src/java.base/share/man/java.1

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  .\" DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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! .\" Title: java
! .\" Language: English
! .\" Date: 03 March 2015
! .\" SectDesc: Basic Tools
! .\" Software: JDK 8
! .\" Arch: generic
! .\" Part Number: E38207-04
! .\" Doc ID: JSSON
  .\"
! .if n .pl 99999
! .TH "java" "1" "03 March 2015" "JDK 8" "Basic Tools"
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! .\" * set default formatting
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! .nh
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! .\" * MAIN CONTENT STARTS HERE *
! .\" -----------------------------------------------------------------
! .SH "NAME"
! java \- Launches a Java application\&.
! .SH "SYNOPSIS"
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fBjava\fR [\fIoptions\fR] \fIclassname\fR [\fIargs\fR]
! .fi
! .if n \{\
! .RE
! .\}
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fBjava\fR [\fIoptions\fR] \fB\-jar\fR \fIfilename\fR [\fIargs\fR]
! .fi
! .if n \{\
! .RE
! .\}
! .PP
! \fIoptions\fR
! .RS 4
! Command\-line options separated by spaces\&. See Options\&.
! .RE
! .PP
! \fIclassname\fR
! .RS 4
! The name of the class to be launched\&.
! .RE
  .PP
! \fIfilename\fR
! .RS 4
! The name of the Java Archive (JAR) file to be called\&. Used only with the
! \fB\-jar\fR
! option\&.
! .RE
! .PP
! \fIargs\fR
! .RS 4
! The arguments passed to the
! \fBmain()\fR
! method separated by spaces\&.
! .RE
! .SH "DESCRIPTION"
! .PP
! The
! \fBjava\fR
! command starts a Java application\&. It does this by starting the Java Runtime Environment (JRE), loading the specified class, and calling that class\*(Aqs
! \fBmain()\fR
! method\&. The method must be declared
! \fIpublic\fR
! and
! \fIstatic\fR, it must not return any value, and it must accept a
! \fBString\fR
! array as a parameter\&. The method declaration has the following form:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fBpublic static void main(String[] args)\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
  .PP
! The
! \fBjava\fR
! command can be used to launch a JavaFX application by loading a class that either has a
! \fBmain()\fR
! method or that extends
! \fBjavafx\&.application\&.Application\fR\&. In the latter case, the launcher constructs an instance of the
! \fBApplication\fR
! class, calls its
! \fBinit()\fR
! method, and then calls the
! \fBstart(javafx\&.stage\&.Stage)\fR
! method\&.
! .PP
! By default, the first argument that is not an option of the
! \fBjava\fR
! command is the fully qualified name of the class to be called\&. If the
! \fB\-jar\fR
! option is specified, its argument is the name of the JAR file containing class and resource files for the application\&. The startup class must be indicated by the
! \fBMain\-Class\fR
! manifest header in its source code\&.
! .PP
! The JRE searches for the startup class (and other classes used by the application) in three sets of locations: the bootstrap class path, the installed extensions, and the user\(cqs class path\&.
! .PP
! Arguments after the class file name or the JAR file name are passed to the
! \fBmain()\fR
! method\&.
! .SH "OPTIONS"
! .PP
! The
! \fBjava\fR
! command supports a wide range of options that can be divided into the following categories:
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Standard Options
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Non\-Standard Options
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Advanced Runtime Options
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Advanced JIT Compiler Options
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Advanced Serviceability Options
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Advanced Garbage Collection Options
! .RE
  .PP
! Standard options are guaranteed to be supported by all implementations of the Java Virtual Machine (JVM)\&. They are used for common actions, such as checking the version of the JRE, setting the class path, enabling verbose output, and so on\&.
  .PP
! Non\-standard options are general purpose options that are specific to the Java HotSpot Virtual Machine, so they are not guaranteed to be supported by all JVM implementations, and are subject to change\&. These options start with
! \fB\-X\fR\&.
  .PP
! Advanced options are not recommended for casual use\&. These are developer options used for tuning specific areas of the Java HotSpot Virtual Machine operation that often have specific system requirements and may require privileged access to system configuration parameters\&. They are also not guaranteed to be supported by all JVM implementations, and are subject to change\&. Advanced options start with
! \fB\-XX\fR\&.
  .PP
! To keep track of the options that were deprecated or removed in the latest release, there is a section named Deprecated and Removed Options at the end of the document\&.
  .PP
! Boolean options are used to either enable a feature that is disabled by default or disable a feature that is enabled by default\&. Such options do not require a parameter\&. Boolean
! \fB\-XX\fR
! options are enabled using the plus sign (\fB\-XX:+\fR\fIOptionName\fR) and disabled using the minus sign (\fB\-XX:\-\fR\fIOptionName\fR)\&.
  .PP
- For options that require an argument, the argument may be separated from the option name by a space, a colon (:), or an equal sign (=), or the argument may directly follow the option (the exact syntax differs for each option)\&. If you are expected to specify the size in bytes, you can use no suffix, or use the suffix
- \fBk\fR
- or
- \fBK\fR
- for kilobytes (KB),
- \fBm\fR
- or
- \fBM\fR
- for megabytes (MB),
- \fBg\fR
  or
- \fBG\fR
- for gigabytes (GB)\&. For example, to set the size to 8 GB, you can specify either
- \fB8g\fR,
- \fB8192m\fR,
- \fB8388608k\fR, or
- \fB8589934592\fR
- as the argument\&. If you are expected to specify the percentage, use a number from 0 to 1 (for example, specify
- \fB0\&.25\fR
- for 25%)\&.
- .SS "Standard Options"
- .PP
- These are the most commonly used options that are supported by all implementations of the JVM\&.
- .PP
- \-agentlib:\fIlibname\fR[=\fIoptions\fR]
- .RS 4
- Loads the specified native agent library\&. After the library name, a comma\-separated list of options specific to the library can be used\&.
- .sp
- If the option
- \fB\-agentlib:foo\fR
- is specified, then the JVM attempts to load the library named
- \fBlibfoo\&.so\fR
- in the location specified by the
- \fBLD_LIBRARY_PATH\fR
- system variable (on OS X this variable is
- \fBDYLD_LIBRARY_PATH\fR)\&.
- .sp
- The following example shows how to load the heap profiling tool (HPROF) library and get sample CPU information every 20 ms, with a stack depth of 3:
- .sp
- .if n \{\
- .RS 4
- .\}
- .nf
- \fB\-agentlib:hprof=cpu=samples,interval=20,depth=3\fR
-  
- .fi
- .if n \{\
- .RE
- .\}
- The following example shows how to load the Java Debug Wire Protocol (JDWP) library and listen for the socket connection on port 8000, suspending the JVM before the main class loads:
- .sp
- .if n \{\
- .RS 4
- .\}
- .nf
- \fB\-agentlib:jdwp=transport=dt_socket,server=y,address=8000\fR
-  
- .fi
- .if n \{\
- .RE
- .\}
- For more information about the native agent libraries, refer to the following:
- .sp
- .RS 4
- .ie n \{\
- \h'-04'\(bu\h'+03'\c
- .\}
- .el \{\
- .sp -1
- .IP \(bu 2.3
- .\}
- The
- \fBjava\&.lang\&.instrument\fR
- package description at http://docs\&.oracle\&.com/javase/8/docs/api/java/lang/instrument/package\-summary\&.html
- .RE
- .sp
- .RS 4
- .ie n \{\
- \h'-04'\(bu\h'+03'\c
- .\}
- .el \{\
- .sp -1
- .IP \(bu 2.3
- .\}
- Agent Command Line Options in the JVM Tools Interface guide at http://docs\&.oracle\&.com/javase/8/docs/platform/jvmti/jvmti\&.html#starting
- .RE
- .RE
- .PP
- \-agentpath:\fIpathname\fR[=\fIoptions\fR]
- .RS 4
- Loads the native agent library specified by the absolute path name\&. This option is equivalent to
- \fB\-agentlib\fR
- but uses the full path and file name of the library\&.
- .RE
- .PP
- \-client
- .RS 4
- Selects the Java HotSpot Client VM\&. The 64\-bit version of the Java SE Development Kit (JDK) currently ignores this option and instead uses the Server JVM\&.
- .sp
- For default JVM selection, see Server\-Class Machine Detection at
- http://docs\&.oracle\&.com/javase/8/docs/technotes/guides/vm/server\-class\&.html
- .RE
- .PP
- \-D\fIproperty\fR=\fIvalue\fR
- .RS 4
- Sets a system property value\&. The
- \fIproperty\fR
- variable is a string with no spaces that represents the name of the property\&. The
- \fIvalue\fR
- variable is a string that represents the value of the property\&. If
- \fIvalue\fR
- is a string with spaces, then enclose it in quotation marks (for example
- \fB\-Dfoo="foo bar"\fR)\&.
- .RE
- .PP
- \-d32
- .RS 4
- Runs the application in a 32\-bit environment\&. If a 32\-bit environment is not installed or is not supported, then an error will be reported\&. By default, the application is run in a 32\-bit environment unless a 64\-bit system is used\&.
- .RE
- .PP
- \-d64
- .RS 4
- Runs the application in a 64\-bit environment\&. If a 64\-bit environment is not installed or is not supported, then an error will be reported\&. By default, the application is run in a 32\-bit environment unless a 64\-bit system is used\&.
- .sp
- Currently only the Java HotSpot Server VM supports 64\-bit operation, and the
- \fB\-server\fR
- option is implicit with the use of
- \fB\-d64\fR\&. The
- \fB\-client\fR
- option is ignored with the use of
- \fB\-d64\fR\&. This is subject to change in a future release\&.
- .RE
- .PP
- \-disableassertions[:[\fIpackagename\fR]\&.\&.\&.|:\fIclassname\fR]
- .br
- \-da[:[\fIpackagename\fR]\&.\&.\&.|:\fIclassname\fR]
- .RS 4
- Disables assertions\&. By default, assertions are disabled in all packages and classes\&.
- .sp
- With no arguments,
- \fB\-disableassertions\fR
- (\fB\-da\fR) disables assertions in all packages and classes\&. With the
- \fIpackagename\fR
- argument ending in
- \fB\&.\&.\&.\fR, the switch disables assertions in the specified package and any subpackages\&. If the argument is simply
- \fB\&.\&.\&.\fR, then the switch disables assertions in the unnamed package in the current working directory\&. With the
- \fIclassname\fR
- argument, the switch disables assertions in the specified class\&.
- .sp
- The
- \fB\-disableassertions\fR
- (\fB\-da\fR) option applies to all class loaders and to system classes (which do not have a class loader)\&. There is one exception to this rule: if the option is provided with no arguments, then it does not apply to system classes\&. This makes it easy to disable assertions in all classes except for system classes\&. The
- \fB\-disablesystemassertions\fR
- option enables you to disable assertions in all system classes\&.
- .sp
- To explicitly enable assertions in specific packages or classes, use the
- \fB\-enableassertions\fR
- (\fB\-ea\fR) option\&. Both options can be used at the same time\&. For example, to run the
- \fBMyClass\fR
- application with assertions enabled in package
- \fBcom\&.wombat\&.fruitbat\fR
- (and any subpackages) but disabled in class
- \fBcom\&.wombat\&.fruitbat\&.Brickbat\fR, use the following command:
- .sp
- .if n \{\
- .RS 4
- .\}
- .nf
- \fBjava \-ea:com\&.wombat\&.fruitbat\&.\&.\&. \-da:com\&.wombat\&.fruitbat\&.Brickbat MyClass\fR
-  
- .fi
- .if n \{\
- .RE
- .\}
- .RE
  .PP
! \-disablesystemassertions
! .br
! \-dsa
! .RS 4
! Disables assertions in all system classes\&.
! .RE
  .PP
! \-enableassertions[:[\fIpackagename\fR]\&.\&.\&.|:\fIclassname\fR]
! .br
! \-ea[:[\fIpackagename\fR]\&.\&.\&.|:\fIclassname\fR]
! .RS 4
! Enables assertions\&. By default, assertions are disabled in all packages and classes\&.
! .sp
! With no arguments,
! \fB\-enableassertions\fR
! (\fB\-ea\fR) enables assertions in all packages and classes\&. With the
! \fIpackagename\fR
! argument ending in
! \fB\&.\&.\&.\fR, the switch enables assertions in the specified package and any subpackages\&. If the argument is simply
! \fB\&.\&.\&.\fR, then the switch enables assertions in the unnamed package in the current working directory\&. With the
! \fIclassname\fR
! argument, the switch enables assertions in the specified class\&.
! .sp
! The
! \fB\-enableassertions\fR
! (\fB\-ea\fR) option applies to all class loaders and to system classes (which do not have a class loader)\&. There is one exception to this rule: if the option is provided with no arguments, then it does not apply to system classes\&. This makes it easy to enable assertions in all classes except for system classes\&. The
! \fB\-enablesystemassertions\fR
! option provides a separate switch to enable assertions in all system classes\&.
! .sp
! To explicitly disable assertions in specific packages or classes, use the
! \fB\-disableassertions\fR
! (\fB\-da\fR) option\&. If a single command contains multiple instances of these switches, then they are processed in order before loading any classes\&. For example, to run the
! \fBMyClass\fR
! application with assertions enabled only in package
! \fBcom\&.wombat\&.fruitbat\fR
! (and any subpackages) but disabled in class
! \fBcom\&.wombat\&.fruitbat\&.Brickbat\fR, use the following command:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fBjava \-ea:com\&.wombat\&.fruitbat\&.\&.\&. \-da:com\&.wombat\&.fruitbat\&.Brickbat MyClass\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \-enablesystemassertions
! .br
! \-esa
! .RS 4
! Enables assertions in all system classes\&.
  .RE
! .PP
! \-help
! .br
! \-?
! .RS 4
! Displays usage information for the
! \fBjava\fR
! command without actually running the JVM\&.
  .RE
! .PP
! \-jar \fIfilename\fR
! .RS 4
! Executes a program encapsulated in a JAR file\&. The
! \fIfilename\fR
! argument is the name of a JAR file with a manifest that contains a line in the form
! \fBMain\-Class:\fR\fIclassname\fR
  that defines the class with the
! \fBpublic static void main(String[] args)\fR
! method that serves as your application\*(Aqs starting point\&.
! .sp
! When you use the
! \fB\-jar\fR
! option, the specified JAR file is the source of all user classes, and other class path settings are ignored\&.
! .sp
! For more information about JAR files, see the following resources:
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! jar(1)
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! The Java Archive (JAR) Files guide at http://docs\&.oracle\&.com/javase/8/docs/technotes/guides/jar/index\&.html
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Lesson: Packaging Programs in JAR Files at
! 
! http://docs\&.oracle\&.com/javase/tutorial/deployment/jar/index\&.html
! .RE
! .RE
! .PP
! \-javaagent:\fIjarpath\fR[=\fIoptions\fR]
! .RS 4
! Loads the specified Java programming language agent\&. For more information about instrumenting Java applications, see the
! \fBjava\&.lang\&.instrument\fR
! package description in the Java API documentation at http://docs\&.oracle\&.com/javase/8/docs/api/java/lang/instrument/package\-summary\&.html
! .RE
! .PP
! \-jre\-restrict\-search
! .RS 4
! Includes user\-private JREs in the version search\&.
! .RE
! .PP
! \-no\-jre\-restrict\-search
! .RS 4
! Excludes user\-private JREs from the version search\&.
! .RE
! .PP
! \-server
! .RS 4
! Selects the Java HotSpot Server VM\&. The 64\-bit version of the JDK supports only the Server VM, so in that case the option is implicit\&.
! .sp
! For default JVM selection, see Server\-Class Machine Detection at
! http://docs\&.oracle\&.com/javase/8/docs/technotes/guides/vm/server\-class\&.html
! .RE
! .PP
! \-showversion
! .RS 4
! Displays version information and continues execution of the application\&. This option is equivalent to the
! \fB\-version\fR
! option except that the latter instructs the JVM to exit after displaying version information\&.
! .RE
! .PP
! \-splash:\fIimgname\fR
! .RS 4
! Shows the splash screen with the image specified by
! \fIimgname\fR\&. For example, to show the
! \fBsplash\&.gif\fR
! file from the
! \fBimages\fR
! directory when starting your application, use the following option:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-splash:images/splash\&.gif\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
! .PP
! \-verbose:class
! .RS 4
! Displays information about each loaded class\&.
! .RE
! .PP
! \-verbose:gc
! .RS 4
! Displays information about each garbage collection (GC) event\&.
! .RE
! .PP
! \-verbose:jni
! .RS 4
! Displays information about the use of native methods and other Java Native Interface (JNI) activity\&.
! .RE
! .PP
! \-version
! .RS 4
! Displays version information and then exits\&. This option is equivalent to the
! \fB\-showversion\fR
! option except that the latter does not instruct the JVM to exit after displaying version information\&.
! .RE
! .PP
! \-version:\fIrelease\fR
! .RS 4
! Specifies the release version to be used for running the application\&. If the version of the
! \fBjava\fR
! command called does not meet this specification and an appropriate implementation is found on the system, then the appropriate implementation will be used\&.
! .sp
! The
! \fIrelease\fR
! argument specifies either the exact version string, or a list of version strings and ranges separated by spaces\&. A
! \fIversion string\fR
! is the developer designation of the version number in the following form:
! \fB1\&.\fR\fIx\fR\fB\&.0_\fR\fIu\fR
! (where
! \fIx\fR
! is the major version number, and
! \fIu\fR
! is the update version number)\&. A
! \fIversion range\fR
! is made up of a version string followed by a plus sign (\fB+\fR) to designate this version or later, or a part of a version string followed by an asterisk (\fB*\fR) to designate any version string with a matching prefix\&. Version strings and ranges can be combined using a space for a logical
! \fIOR\fR
! combination, or an ampersand (\fB&\fR) for a logical
! \fIAND\fR
! combination of two version strings/ranges\&. For example, if running the class or JAR file requires either JRE 6u13 (1\&.6\&.0_13), or any JRE 6 starting from 6u10 (1\&.6\&.0_10), specify the following:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-version:"1\&.6\&.0_13 1\&.6* & 1\&.6\&.0_10+"\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Quotation marks are necessary only if there are spaces in the
! \fIrelease\fR
! parameter\&.
! .sp
! For JAR files, the preference is to specify version requirements in the JAR file manifest rather than on the command line\&.
! .RE
! .SS "Non\-Standard Options"
! .PP
! These options are general purpose options that are specific to the Java HotSpot Virtual Machine\&.
! .PP
! \-X
! .RS 4
! Displays help for all available
! \fB\-X\fR
! options\&.
! .RE
! .PP
! \-Xbatch
! .RS 4
! Disables background compilation\&. By default, the JVM compiles the method as a background task, running the method in interpreter mode until the background compilation is finished\&. The
! \fB\-Xbatch\fR
! flag disables background compilation so that compilation of all methods proceeds as a foreground task until completed\&.
! .sp
! This option is equivalent to
! \fB\-XX:\-BackgroundCompilation\fR\&.
! .RE
! .PP
! \-Xbootclasspath:\fIpath\fR
! .RS 4
! Specifies a list of directories, JAR files, and ZIP archives separated by colons (:) to search for boot class files\&. These are used in place of the boot class files included in the JDK\&.
! .sp
! Do not deploy applications that use this option to override a class in
! \fBrt\&.jar\fR, because this violates the JRE binary code license\&.
! .RE
! .PP
! \-Xbootclasspath/a:\fIpath\fR
! .RS 4
! Specifies a list of directories, JAR files, and ZIP archives separated by colons (:) to append to the end of the default bootstrap class path\&.
! .sp
! Do not deploy applications that use this option to override a class in
! \fBrt\&.jar\fR, because this violates the JRE binary code license\&.
! .RE
! .PP
! \-Xbootclasspath/p:\fIpath\fR
! .RS 4
! Specifies a list of directories, JAR files, and ZIP archives separated by colons (:) to prepend to the front of the default bootstrap class path\&.
! .sp
! Do not deploy applications that use this option to override a class in
! \fBrt\&.jar\fR, because this violates the JRE binary code license\&.
! .RE
! .PP
! \-Xcheck:jni
! .RS 4
! Performs additional checks for Java Native Interface (JNI) functions\&. Specifically, it validates the parameters passed to the JNI function and the runtime environment data before processing the JNI request\&. Any invalid data encountered indicates a problem in the native code, and the JVM will terminate with an irrecoverable error in such cases\&. Expect a performance degradation when this option is used\&.
! .RE
! .PP
! \-Xcomp
! .RS 4
! Forces compilation of methods on first invocation\&. By default, the Client VM (\fB\-client\fR) performs 1,000 interpreted method invocations and the Server VM (\fB\-server\fR) performs 10,000 interpreted method invocations to gather information for efficient compilation\&. Specifying the
! \fB\-Xcomp\fR
! option disables interpreted method invocations to increase compilation performance at the expense of efficiency\&.
! .sp
! You can also change the number of interpreted method invocations before compilation using the
! \fB\-XX:CompileThreshold\fR
! option\&.
! .RE
! .PP
! \-Xdebug
! .RS 4
! Does nothing\&. Provided for backward compatibility\&.
! .RE
! .PP
! \-Xdiag
! .RS 4
! Shows additional diagnostic messages\&.
! .RE
! .PP
! \-Xfuture
! .RS 4
! Enables strict class\-file format checks that enforce close conformance to the class\-file format specification\&. Developers are encouraged to use this flag when developing new code because the stricter checks will become the default in future releases\&.
! .sp
! This option is deprecated and may be removed in a future release.
! .RE
! .PP
! \-Xint
! .RS 4
! Runs the application in interpreted\-only mode\&. Compilation to native code is disabled, and all bytecode is executed by the interpreter\&. The performance benefits offered by the just in time (JIT) compiler are not present in this mode\&.
  .RE
! .PP
! \-Xinternalversion
! .RS 4
  Displays more detailed JVM version information than the
! \fB\-version\fR
! option, and then exits\&.
  .RE
! .PP
! \-Xloggc:\fIfilename\fR
! .RS 4
! Sets the file to which verbose GC events information should be redirected for logging\&. The information written to this file is similar to the output of
! \fB\-verbose:gc\fR
! with the time elapsed since the first GC event preceding each logged event\&. The
! \fB\-Xloggc\fR
! option overrides
! \fB\-verbose:gc\fR
! if both are given with the same
! \fBjava\fR
! command\&.
! .sp
! Example:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-Xloggc:garbage\-collection\&.log\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
! .PP
! \-Xmaxjitcodesize=\fIsize\fR
! .RS 4
! Specifies the maximum code cache size (in bytes) for JIT\-compiled code\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. The default maximum code cache size is 240 MB; if you disable tiered compilation with the option
! \fB\-XX:\-TieredCompilation\fR, then the default size is 48 MB:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-Xmaxjitcodesize=240m\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! This option is equivalent to
! \fB\-XX:ReservedCodeCacheSize\fR\&.
! .RE
! .PP
! \-Xmixed
! .RS 4
! Executes all bytecode by the interpreter except for hot methods, which are compiled to native code\&.
! .RE
! .PP
! \-Xmn\fIsize\fR
! .RS 4
! Sets the initial and maximum size (in bytes) of the heap for the young generation (nursery)\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&.
! .sp
! The young generation region of the heap is used for new objects\&. GC is performed in this region more often than in other regions\&. If the size for the young generation is too small, then a lot of minor garbage collections will be performed\&. If the size is too large, then only full garbage collections will be performed, which can take a long time to complete\&. Oracle recommends that you keep the size for the young generation between a half and a quarter of the overall heap size\&.
! .sp
! The following examples show how to set the initial and maximum size of young generation to 256 MB using various units:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-Xmn256m\fR
! \fB\-Xmn262144k\fR
! \fB\-Xmn268435456\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Instead of the
! \fB\-Xmn\fR
! option to set both the initial and maximum size of the heap for the young generation, you can use
! \fB\-XX:NewSize\fR
! to set the initial size and
! \fB\-XX:MaxNewSize\fR
! to set the maximum size\&.
! .RE
! .PP
! \-Xms\fIsize\fR
! .RS 4
! Sets the initial size (in bytes) of the heap\&. This value must be a multiple of 1024 and greater than 1 MB\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&.
! .sp
! The following examples show how to set the size of allocated memory to 6 MB using various units:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-Xms6291456\fR
! \fB\-Xms6144k\fR
! \fB\-Xms6m\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! If you do not set this option, then the initial size will be set as the sum of the sizes allocated for the old generation and the young generation\&. The initial size of the heap for the young generation can be set using the
! \fB\-Xmn\fR
! option or the
! \fB\-XX:NewSize\fR
! option\&.
! .RE
! .PP
! \-Xmx\fIsize\fR
! .RS 4
! Specifies the maximum size (in bytes) of the memory allocation pool in bytes\&. This value must be a multiple of 1024 and greater than 2 MB\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. The default value is chosen at runtime based on system configuration\&. For server deployments,
! \fB\-Xms\fR
! and
! \fB\-Xmx\fR
! are often set to the same value\&. See the section "Ergonomics" in
! \fIJava SE HotSpot Virtual Machine Garbage Collection Tuning Guide\fR
! at http://docs\&.oracle\&.com/javase/8/docs/technotes/guides/vm/gctuning/index\&.html\&.
! .sp
! The following examples show how to set the maximum allowed size of allocated memory to 80 MB using various units:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-Xmx83886080\fR
! \fB\-Xmx81920k\fR
! \fB\-Xmx80m\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! The
! \fB\-Xmx\fR
! option is equivalent to
! \fB\-XX:MaxHeapSize\fR\&.
! .RE
! .PP
! \-Xnoclassgc
! .RS 4
! Disables garbage collection (GC) of classes\&. This can save some GC time, which shortens interruptions during the application run\&.
! .sp
! When you specify
! \fB\-Xnoclassgc\fR
! at startup, the class objects in the application will be left untouched during GC and will always be considered live\&. This can result in more memory being permanently occupied which, if not used carefully, will throw an out of memory exception\&.
! .RE
! .PP
! \-Xprof
! .RS 4
! Profiles the running program and sends profiling data to standard output\&. This option is provided as a utility that is useful in program development and is not intended to be used in production systems\&.
! .RE
! .PP
! \-Xrs
! .RS 4
! Reduces the use of operating system signals by the JVM\&.
! .sp
! Shutdown hooks enable orderly shutdown of a Java application by running user cleanup code (such as closing database connections) at shutdown, even if the JVM terminates abruptly\&.
! .sp
! The JVM catches signals to implement shutdown hooks for unexpected termination\&. The JVM uses
! \fBSIGHUP\fR,
! \fBSIGINT\fR, and
! \fBSIGTERM\fR
! to initiate the running of shutdown hooks\&.
! .sp
! The JVM uses a similar mechanism to implement the feature of dumping thread stacks for debugging purposes\&. The JVM uses
! \fBSIGQUIT\fR
! to perform thread dumps\&.
! .sp
  Applications embedding the JVM frequently need to trap signals such as
! \fBSIGINT\fR
! or
! \fBSIGTERM\fR, which can lead to interference with the JVM signal handlers\&. The
! \fB\-Xrs\fR
! option is available to address this issue\&. When
! \fB\-Xrs\fR
! is used, the signal masks for
! \fBSIGINT\fR,
! \fBSIGTERM\fR,
! \fBSIGHUP\fR, and
! \fBSIGQUIT\fR
! are not changed by the JVM, and signal handlers for these signals are not installed\&.
! .sp
! There are two consequences of specifying
! \fB\-Xrs\fR:
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! \fBSIGQUIT\fR
! thread dumps are not available\&.
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! User code is responsible for causing shutdown hooks to run, for example, by calling
! \fBSystem\&.exit()\fR
! when the JVM is to be terminated\&.
! .RE
! .RE
! .PP
! \-Xshare:\fImode\fR
! .RS 4
! Sets the class data sharing (CDS) mode\&. Possible
! \fImode\fR
! arguments for this option include the following:
! .PP
! auto
! .RS 4
! Use CDS if possible\&. This is the default value for Java HotSpot 32\-Bit Client VM\&.
! .RE
! .PP
! on
! .RS 4
! Require the use of CDS\&. Print an error message and exit if class data sharing cannot be used\&.
! .RE
! .PP
! off
! .RS 4
! Do not use CDS\&. This is the default value for Java HotSpot 32\-Bit Server VM, Java HotSpot 64\-Bit Client VM, and Java HotSpot 64\-Bit Server VM\&.
! .RE
! .PP
! dump
! .RS 4
! Manually generate the CDS archive\&. Specify the application class path as described in "Setting the Class Path "\&.
! .sp
! You should regenerate the CDS archive with each new JDK release\&.
! .RE
! .RE
! .PP
! \-XshowSettings:\fIcategory\fR
! .RS 4
! Shows settings and continues\&. Possible
! \fIcategory\fR
! arguments for this option include the following:
! .PP
! all
! .RS 4
! Shows all categories of settings\&. This is the default value\&.
! .RE
! .PP
! locale
! .RS 4
! Shows settings related to locale\&.
! .RE
! .PP
! properties
! .RS 4
! Shows settings related to system properties\&.
! .RE
! .PP
! vm
! .RS 4
! Shows the settings of the JVM\&.
! .RE
! .RE
! .PP
! \-Xss\fIsize\fR
! .RS 4
! Sets the thread stack size (in bytes)\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate KB,
! \fBm\fR
! or
! \fBM\fR
! to indicate MB,
! \fBg\fR
! or
! \fBG\fR
! to indicate GB\&. The default value depends on the platform:
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Linux/ARM (32\-bit): 320 KB
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Linux/i386 (32\-bit): 320 KB
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
  Linux/x64 (64\-bit): 1024 KB
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! OS X (64\-bit): 1024 KB
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Oracle Solaris/i386 (32\-bit): 320 KB
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Oracle Solaris/x64 (64\-bit): 1024 KB
! .RE
! .sp
! The following examples set the thread stack size to 1024 KB in different units:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-Xss1m\fR
! \fB\-Xss1024k\fR
! \fB\-Xss1048576\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! This option is equivalent to
! \fB\-XX:ThreadStackSize\fR\&.
! .RE
! .PP
! \-Xusealtsigs
! .RS 4
! Use alternative signals instead of
! \fBSIGUSR1\fR
! and
! \fBSIGUSR2\fR
! for JVM internal signals\&. This option is equivalent to
! \fB\-XX:+UseAltSigs\fR\&.
! .RE
! .PP
! \-Xverify:\fImode\fR
! .RS 4
! Sets the mode of the bytecode verifier\&. Bytecode verification helps to troubleshoot some problems, but it also adds overhead to the running application\&. Possible
! \fImode\fR
! arguments for this option include the following:
! .PP
! none
! .RS 4
! Do not verify the bytecode\&. This reduces startup time and also reduces the protection provided by Java\&.
! .sp
! This option is deprecated and may be removed in a future release.
! .RE
! .PP
! remote
! .RS 4
! Verify those classes that are not loaded by the bootstrap class loader\&. This is the default behavior if you do not specify the
! \fB\-Xverify\fR
! option\&.
! .RE
! .PP
! all
! .RS 4
! Verify all classes\&.
! .RE
! .RE
! .SS "Advanced Runtime Options"
! .PP
! These options control the runtime behavior of the Java HotSpot VM\&.
! .PP
! \-XX:+DisableAttachMechanism
! .RS 4
! Enables the option that disables the mechanism that lets tools attach to the JVM\&. By default, this option is disabled, meaning that the attach mechanism is enabled and you can use tools such as
! \fBjcmd\fR,
! \fBjstack\fR,
! \fBjmap\fR, and
! \fBjinfo\fR\&.
! .RE
! .PP
! \-XX:ErrorFile=\fIfilename\fR
! .RS 4
! Specifies the path and file name to which error data is written when an irrecoverable error occurs\&. By default, this file is created in the current working directory and named
! \fBhs_err_pid\fR\fIpid\fR\fB\&.log\fR
! where
! \fIpid\fR
! is the identifier of the process that caused the error\&. The following example shows how to set the default log file (note that the identifier of the process is specified as
! \fB%p\fR):
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:ErrorFile=\&./hs_err_pid%p\&.log\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! The following example shows how to set the error log to
! \fB/var/log/java/java_error\&.log\fR:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:ErrorFile=/var/log/java/java_error\&.log\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! If the file cannot be created in the specified directory (due to insufficient space, permission problem, or another issue), then the file is created in the temporary directory for the operating system\&. The temporary directory is
! \fB/tmp\fR\&.
! .RE
! .PP
! \-XX:+FailOverToOldVerifier
! .RS 4
! Enables automatic failover to the old verifier when the new type checker fails\&. By default, this option is disabled and it is ignored (that is, treated as disabled) for classes with a recent bytecode version\&. You can enable it for classes with older versions of the bytecode\&.
! .RE
  .PP
- \-XX:LargePageSizeInBytes=\fIsize\fR
- .RS 4
- On Solaris, sets the maximum size (in bytes) for large pages used for Java heap\&. The
- \fIsize\fR
- argument must be a power of 2 (2, 4, 8, 16, \&.\&.\&.)\&. Append the letter
- \fBk\fR
- or
- \fBK\fR
- to indicate kilobytes,
- \fBm\fR
- or
- \fBM\fR
- to indicate megabytes,
- \fBg\fR
- or
- \fBG\fR
- to indicate gigabytes\&. By default, the size is set to 0, meaning that the JVM chooses the size for large pages automatically\&.
- .sp
- The following example illustrates how to set the large page size to 4 megabytes (MB):
- .sp
- .if n \{\
- .RS 4
- .\}
- .nf
- \fB\-XX:LargePageSizeInBytes=4m\fR
-  
- .fi
- .if n \{\
- .RE
- .\}
- .RE
- .PP
- \-XX:MaxDirectMemorySize=\fIsize\fR
- .RS 4
- Sets the maximum total size (in bytes) of the New I/O (the
- \fBjava\&.nio\fR
- package) direct\-buffer allocations\&. Append the letter
- \fBk\fR
- or
- \fBK\fR
- to indicate kilobytes,
- \fBm\fR
- or
- \fBM\fR
- to indicate megabytes,
- \fBg\fR
- or
- \fBG\fR
- to indicate gigabytes\&. By default, the size is set to 0, meaning that the JVM chooses the size for NIO direct\-buffer allocations automatically\&.
- .sp
- The following examples illustrate how to set the NIO size to 1024 KB in different units:
- .sp
- .if n \{\
- .RS 4
- .\}
- .nf
- \fB\-XX:MaxDirectMemorySize=1m\fR
- \fB\-XX:MaxDirectMemorySize=1024k\fR
- \fB\-XX:MaxDirectMemorySize=1048576\fR
-  
- .fi
- .if n \{\
- .RE
- .\}
- .RE
- .PP
- \-XX:NativeMemoryTracking=\fImode\fR
- .RS 4
- Specifies the mode for tracking JVM native memory usage\&. Possible
- \fImode\fR
- arguments for this option include the following:
- .PP
- off
- .RS 4
- Do not track JVM native memory usage\&. This is the default behavior if you do not specify the
- \fB\-XX:NativeMemoryTracking\fR
- option\&.
- .RE
- .PP
- summary
- .RS 4
- Only track memory usage by JVM subsystems, such as Java heap, class, code, and thread\&.
- .RE
- .PP
- detail
- .RS 4
- In addition to tracking memory usage by JVM subsystems, track memory usage by individual
- \fBCallSite\fR, individual virtual memory region and its committed regions\&.
- .RE
- .RE
- .PP
- \-XX:ObjectAlignmentInBytes=\fIalignment\fR
- .RS 4
- Sets the memory alignment of Java objects (in bytes)\&. By default, the value is set to 8 bytes\&. The specified value should be a power of two, and must be within the range of 8 and 256 (inclusive)\&. This option makes it possible to use compressed pointers with large Java heap sizes\&.
- .sp
  The heap size limit in bytes is calculated as:
! .sp
! \fB4GB * ObjectAlignmentInBytes\fR
! .sp
! Note: As the alignment value increases, the unused space between objects will also increase\&. As a result, you may not realize any benefits from using compressed pointers with large Java heap sizes\&.
! .RE
  .PP
! \-XX:OnError=\fIstring\fR
! .RS 4
! Sets a custom command or a series of semicolon\-separated commands to run when an irrecoverable error occurs\&. If the string contains spaces, then it must be enclosed in quotation marks\&.
! .sp
! The following example shows how the
! \fB\-XX:OnError\fR
! option can be used to run the
! \fBgcore\fR
! command to create the core image, and the debugger is started to attach to the process in case of an irrecoverable error (the
! \fB%p\fR
! designates the current process):
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:OnError="gcore %p;dbx \- %p"\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
! .PP
! \-XX:OnOutOfMemoryError=\fIstring\fR
! .RS 4
! Sets a custom command or a series of semicolon\-separated commands to run when an
! \fBOutOfMemoryError\fR
! exception is first thrown\&. If the string contains spaces, then it must be enclosed in quotation marks\&. For an example of a command string, see the description of the
! \fB\-XX:OnError\fR
! option\&.
! .RE
! .PP
! \-XX:+PerfDataSaveToFile
! .RS 4
! If enabled, saves
! jstat(1) binary data when the Java application exits\&. This binary data is saved in a file named
! \fBhsperfdata_\fR\fI<pid>\fR, where
! \fI<pid>\fR
! is the process identifier of the Java application you ran\&. Use
! \fBjstat\fR
! to display the performance data contained in this file as follows:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fBjstat \-class file:///\fR\fB\fI<path>\fR\fR\fB/hsperfdata_\fR\fB\fI<pid>\fR\fR
! \fBjstat \-gc file:///\fR\fB\fI<path>\fR\fR\fB/hsperfdata_\fR\fB\fI<pid>\fR\fR
! .fi
! .if n \{\
! .RE
! .\}
  .RE
  .PP
! \-XX:+PrintCommandLineFlags
! .RS 4
! Enables printing of ergonomically selected JVM flags that appeared on the command line\&. It can be useful to know the ergonomic values set by the JVM, such as the heap space size and the selected garbage collector\&. By default, this option is disabled and flags are not printed\&.
! .RE
! .PP
! \-XX:+PrintNMTStatistics
! .RS 4
! Enables printing of collected native memory tracking data at JVM exit when native memory tracking is enabled (see
! \fB\-XX:NativeMemoryTracking\fR)\&. By default, this option is disabled and native memory tracking data is not printed\&.
! .RE
! .PP
! \-XX:+ShowMessageBoxOnError
! .RS 4
! Enables displaying of a dialog box when the JVM experiences an irrecoverable error\&. This prevents the JVM from exiting and keeps the process active so that you can attach a debugger to it to investigate the cause of the error\&. By default, this option is disabled\&.
! .RE
! .PP
! \-XX:ThreadStackSize=\fIsize\fR
! .RS 4
! Sets the thread stack size (in bytes)\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. The default value depends on the platform:
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Linux/ARM (32\-bit): 320 KB
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Linux/i386 (32\-bit): 320 KB
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
  Linux/x64 (64\-bit): 1024 KB
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! OS X (64\-bit): 1024 KB
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Oracle Solaris/i386 (32\-bit): 320 KB
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Oracle Solaris/x64 (64\-bit): 1024 KB
! .RE
! .sp
! The following examples show how to set the thread stack size to 1024 KB in different units:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:ThreadStackSize=1m\fR
! \fB\-XX:ThreadStackSize=1024k\fR
! \fB\-XX:ThreadStackSize=1048576\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! This option is equivalent to
! \fB\-Xss\fR\&.
! .RE
! .PP
! \-XX:+TraceClassLoading
! .RS 4
! Enables tracing of classes as they are loaded\&. By default, this option is disabled and classes are not traced\&.
! .RE
! .PP
! \-XX:+TraceClassLoadingPreorder
! .RS 4
! Enables tracing of all loaded classes in the order in which they are referenced\&. By default, this option is disabled and classes are not traced\&.
! .RE
! .PP
! \-XX:+TraceClassResolution
! .RS 4
! Enables tracing of constant pool resolutions\&. By default, this option is disabled and constant pool resolutions are not traced\&.
! .RE
! .PP
! \-XX:+TraceClassUnloading
! .RS 4
! Enables tracing of classes as they are unloaded\&. By default, this option is disabled and classes are not traced\&.
! .RE
! .PP
! \-XX:+TraceLoaderConstraints
! .RS 4
! Enables tracing of the loader constraints recording\&. By default, this option is disabled and loader constraints recording is not traced\&.
! .RE
! .PP
! \-XX:+UseAltSigs
! .RS 4
! Enables the use of alternative signals instead of
! \fBSIGUSR1\fR
! and
! \fBSIGUSR2\fR
! for JVM internal signals\&. By default, this option is disabled and alternative signals are not used\&. This option is equivalent to
! \fB\-Xusealtsigs\fR\&.
! .RE
! .PP
! \-XX:\-UseBiasedLocking
! .RS 4
! Disables the use of biased locking\&. Some applications with significant amounts of uncontended synchronization may attain significant speedups with this flag enabled, whereas applications with certain patterns of locking may see slowdowns\&. For more information about the biased locking technique, see the example in Java Tuning White Paper at http://www\&.oracle\&.com/technetwork/java/tuning\-139912\&.html#section4\&.2\&.5
! .sp
! By default, this option is enabled\&.
! .RE
! .PP
! \-XX:\-UseCompressedOops
! .RS 4
! Disables the use of compressed pointers\&. By default, this option is enabled, and compressed pointers are used when Java heap sizes are less than 32 GB\&. When this option is enabled, object references are represented as 32\-bit offsets instead of 64\-bit pointers, which typically increases performance when running the application with Java heap sizes less than 32 GB\&. This option works only for 64\-bit JVMs\&.
! .sp
! It is also possible to use compressed pointers when Java heap sizes are greater than 32GB\&. See the
! \fB\-XX:ObjectAlignmentInBytes\fR
! option\&.
! .RE
! .PP
! \-XX:+UseHugeTLBFS
! .RS 4
! This option for Linux is the equivalent of specifying
! \fB\-XX:+UseLargePages\fR\&. This option is disabled by default\&. This option pre\-allocates all large pages up\-front, when memory is reserved; consequently the JVM cannot dynamically grow or shrink large pages memory areas; see
! \fB\-XX:UseTransparentHugePages\fR
! if you want this behavior\&.
! .sp
! For more information, see "Large Pages"\&.
! .RE
! .PP
! \-XX:+UseLargePages
! .RS 4
! Enables the use of large page memory\&. By default, this option is disabled and large page memory is not used\&.
! .sp
! For more information, see "Large Pages"\&.
! .RE
! .PP
! \-XX:+UseMembar
! .RS 4
! Enables issuing of membars on thread state transitions\&. This option is disabled by default on all platforms except ARM servers, where it is enabled\&. (It is recommended that you do not disable this option on ARM servers\&.)
! .RE
! .PP
! \-XX:+UsePerfData
! .RS 4
! Enables the
! \fBperfdata\fR
! feature\&. This option is enabled by default to allow JVM monitoring and performance testing\&. Disabling it suppresses the creation of the
! \fBhsperfdata_userid\fR
! directories\&. To disable the
! \fBperfdata\fR
! feature, specify
! \fB\-XX:\-UsePerfData\fR\&.
! .RE
! .PP
! \-XX:+UseTransparentHugePages
! .RS 4
! On Linux, enables the use of large pages that can dynamically grow or shrink\&. This option is disabled by default\&. You may encounter performance problems with transparent huge pages as the OS moves other pages around to create huge pages; this option is made available for experimentation\&.
! .sp
! For more information, see "Large Pages"\&.
! .RE
! .PP
! \-XX:+AllowUserSignalHandlers
! .RS 4
! Enables installation of signal handlers by the application\&. By default, this option is disabled and the application is not allowed to install signal handlers\&.
! .RE
! .SS "Advanced JIT Compiler Options"
! .PP
! These options control the dynamic just\-in\-time (JIT) compilation performed by the Java HotSpot VM\&.
! .PP
! \-XX:AllocateInstancePrefetchLines=\fIlines\fR
! .RS 4
! Sets the number of lines to prefetch ahead of the instance allocation pointer\&. By default, the number of lines to prefetch is set to 1:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:AllocateInstancePrefetchLines=1\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Only the Java HotSpot Server VM supports this option\&.
! .RE
! .PP
! \-XX:AllocatePrefetchDistance=\fIsize\fR
! .RS 4
! Sets the size (in bytes) of the prefetch distance for object allocation\&. Memory about to be written with the value of new objects is prefetched up to this distance starting from the address of the last allocated object\&. Each Java thread has its own allocation point\&.
! .sp
! Negative values denote that prefetch distance is chosen based on the platform\&. Positive values are bytes to prefetch\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. The default value is set to \-1\&.
! .sp
! The following example shows how to set the prefetch distance to 1024 bytes:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:AllocatePrefetchDistance=1024\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Only the Java HotSpot Server VM supports this option\&.
! .RE
! .PP
! \-XX:AllocatePrefetchInstr=\fIinstruction\fR
! .RS 4
! Sets the prefetch instruction to prefetch ahead of the allocation pointer\&. Only the Java HotSpot Server VM supports this option\&. Possible values are from 0 to 3\&. The actual instructions behind the values depend on the platform\&. By default, the prefetch instruction is set to 0:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:AllocatePrefetchInstr=0\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Only the Java HotSpot Server VM supports this option\&.
! .RE
! .PP
! \-XX:AllocatePrefetchLines=\fIlines\fR
! .RS 4
! Sets the number of cache lines to load after the last object allocation by using the prefetch instructions generated in compiled code\&. The default value is 1 if the last allocated object was an instance, and 3 if it was an array\&.
! .sp
! The following example shows how to set the number of loaded cache lines to 5:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:AllocatePrefetchLines=5\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Only the Java HotSpot Server VM supports this option\&.
! .RE
! .PP
! \-XX:AllocatePrefetchStepSize=\fIsize\fR
! .RS 4
! Sets the step size (in bytes) for sequential prefetch instructions\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. By default, the step size is set to 16 bytes:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:AllocatePrefetchStepSize=16\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Only the Java HotSpot Server VM supports this option\&.
! .RE
! .PP
! \-XX:AllocatePrefetchStyle=\fIstyle\fR
! .RS 4
! Sets the generated code style for prefetch instructions\&. The
! \fIstyle\fR
! argument is an integer from 0 to 3:
! .PP
! 0
! .RS 4
! Do not generate prefetch instructions\&.
! .RE
! .PP
! 1
! .RS 4
! Execute prefetch instructions after each allocation\&. This is the default parameter\&.
! .RE
! .PP
! 2
! .RS 4
! Use the thread\-local allocation block (TLAB) watermark pointer to determine when prefetch instructions are executed\&.
! .RE
! .PP
! 3
! .RS 4
! Use BIS instruction on SPARC for allocation prefetch\&.
! .RE
! .sp
! Only the Java HotSpot Server VM supports this option\&.
! .RE
! .PP
! \-XX:+BackgroundCompilation
! .RS 4
! Enables background compilation\&. This option is enabled by default\&. To disable background compilation, specify
! \fB\-XX:\-BackgroundCompilation\fR
! (this is equivalent to specifying
! \fB\-Xbatch\fR)\&.
! .RE
! .PP
! \-XX:CICompilerCount=\fIthreads\fR
! .RS 4
! Sets the number of compiler threads to use for compilation\&. By default, the number of threads is set to 2 for the server JVM, to 1 for the client JVM, and it scales to the number of cores if tiered compilation is used\&. The following example shows how to set the number of threads to 2:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CICompilerCount=2\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
! .PP
! \-XX:CodeCacheMinimumFreeSpace=\fIsize\fR
! .RS 4
! Sets the minimum free space (in bytes) required for compilation\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. When less than the minimum free space remains, compiling stops\&. By default, this option is set to 500 KB\&. The following example shows how to set the minimum free space to 1024 MB:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CodeCacheMinimumFreeSpace=1024m\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
! .PP
! \-XX:CompileCommand=\fIcommand\fR,\fImethod\fR[,\fIoption\fR]
! .RS 4
! Specifies a command to perform on a method\&. For example, to exclude the
! \fBindexOf()\fR
! method of the
! \fBString\fR
! class from being compiled, use the following:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CompileCommand=exclude,java/lang/String\&.indexOf\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Note that the full class name is specified, including all packages and subpackages separated by a slash (\fB/\fR)\&. For easier cut and paste operations, it is also possible to use the method name format produced by the
! \fB\-XX:+PrintCompilation\fR
! and
! \fB\-XX:+LogCompilation\fR
! options:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CompileCommand=exclude,java\&.lang\&.String::indexOf\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! If the method is specified without the signature, the command will be applied to all methods with the specified name\&. However, you can also specify the signature of the method in the class file format\&. In this case, you should enclose the arguments in quotation marks, because otherwise the shell treats the semicolon as command end\&. For example, if you want to exclude only the
! \fBindexOf(String)\fR
! method of the
! \fBString\fR
! class from being compiled, use the following:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CompileCommand="exclude,java/lang/String\&.indexOf,(Ljava/lang/String;)I"\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! You can also use the asterisk (*) as a wildcard for class and method names\&. For example, to exclude all
! \fBindexOf()\fR
! methods in all classes from being compiled, use the following:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CompileCommand=exclude,*\&.indexOf\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! The commas and periods are aliases for spaces, making it easier to pass compiler commands through a shell\&. You can pass arguments to
! \fB\-XX:CompileCommand\fR
! using spaces as separators by enclosing the argument in quotation marks:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CompileCommand="exclude java/lang/String indexOf"\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Note that after parsing the commands passed on the command line using the
! \fB\-XX:CompileCommand\fR
! options, the JIT compiler then reads commands from the
! \fB\&.hotspot_compiler\fR
! file\&. You can add commands to this file or specify a different file using the
! \fB\-XX:CompileCommandFile\fR
! option\&.
! .sp
! To add several commands, either specify the
! \fB\-XX:CompileCommand\fR
! option multiple times, or separate each argument with the newline separator (\fB\en\fR)\&. The following commands are available:
! .PP
! break
! .RS 4
! Set a breakpoint when debugging the JVM to stop at the beginning of compilation of the specified method\&.
! .RE
! .PP
! compileonly
! .RS 4
! Exclude all methods from compilation except for the specified method\&. As an alternative, you can use the
! \fB\-XX:CompileOnly\fR
! option, which allows to specify several methods\&.
! .RE
! .PP
! dontinline
! .RS 4
! Prevent inlining of the specified method\&.
! .RE
! .PP
! exclude
! .RS 4
! Exclude the specified method from compilation\&.
! .RE
! .PP
! help
! .RS 4
! Print a help message for the
! \fB\-XX:CompileCommand\fR
! option\&.
! .RE
! .PP
! inline
! .RS 4
! Attempt to inline the specified method\&.
! .RE
! .PP
! log
! .RS 4
! Exclude compilation logging (with the
! \fB\-XX:+LogCompilation\fR
! option) for all methods except for the specified method\&. By default, logging is performed for all compiled methods\&.
! .RE
! .PP
! option
! .RS 4
! This command can be used to pass a JIT compilation option to the specified method in place of the last argument (\fIoption\fR)\&. The compilation option is set at the end, after the method name\&. For example, to enable the
! \fBBlockLayoutByFrequency\fR
! option for the
! \fBappend()\fR
! method of the
! \fBStringBuffer\fR
! class, use the following:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CompileCommand=option,java/lang/StringBuffer\&.append,BlockLayoutByFrequency\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! You can specify multiple compilation options, separated by commas or spaces\&.
! .RE
  .PP
! print
! .RS 4
! Print generated assembler code after compilation of the specified method\&.
  .RE
  .PP
- quiet
- .RS 4
- Do not print the compile commands\&. By default, the commands that you specify with the \-\fBXX:CompileCommand\fR
- option are printed; for example, if you exclude from compilation the
- \fBindexOf()\fR
- method of the
- \fBString\fR
- class, then the following will be printed to standard output:
- .sp
- .if n \{\
- .RS 4
- .\}
- .nf
- \fBCompilerOracle: exclude java/lang/String\&.indexOf\fR
-  
- .fi
- .if n \{\
- .RE
- .\}
  You can suppress this by specifying the
! \fB\-XX:CompileCommand=quiet\fR
! option before other
! \fB\-XX:CompileCommand\fR
! options\&.
  .RE
  .RE
! .PP
! \-XX:CompileCommandFile=\fIfilename\fR
! .RS 4
! Sets the file from which JIT compiler commands are read\&. By default, the
! \fB\&.hotspot_compiler\fR
! file is used to store commands performed by the JIT compiler\&.
! .sp
! Each line in the command file represents a command, a class name, and a method name for which the command is used\&. For example, this line prints assembly code for the
! \fBtoString()\fR
! method of the
! \fBString\fR
  class:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fBprint java/lang/String toString\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! For more information about specifying the commands for the JIT compiler to perform on methods, see the
! \fB\-XX:CompileCommand\fR
! option\&.
! .RE
! .PP
! \-XX:CompileOnly=\fImethods\fR
! .RS 4
! Sets the list of methods (separated by commas) to which compilation should be restricted\&. Only the specified methods will be compiled\&. Specify each method with the full class name (including the packages and subpackages)\&. For example, to compile only the
! \fBlength()\fR
! method of the
! \fBString\fR
! class and the
! \fBsize()\fR
! method of the
! \fBList\fR
! class, use the following:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CompileOnly=java/lang/String\&.length,java/util/List\&.size\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Note that the full class name is specified, including all packages and subpackages separated by a slash (\fB/\fR)\&. For easier cut and paste operations, it is also possible to use the method name format produced by the
! \fB\-XX:+PrintCompilation\fR
! and
! \fB\-XX:+LogCompilation\fR
! options:
! .sp
! .if n \{\
! .RS 4
! .\}
  .nf
! \fB\-XX:CompileOnly=java\&.lang\&.String::length,java\&.util\&.List::size\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Although wildcards are not supported, you can specify only the class or package name to compile all methods in that class or package, as well as specify just the method to compile methods with this name in any class:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CompileOnly=java/lang/String\fR
! \fB\-XX:CompileOnly=java/lang\fR
! \fB\-XX:CompileOnly=\&.length\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \-XX:CompileThreshold=\fIinvocations\fR
! .RS 4
! Sets the number of interpreted method invocations before compilation\&. By default, in the server JVM, the JIT compiler performs 10,000 interpreted method invocations to gather information for efficient compilation\&. For the client JVM, the default setting is 1,500 invocations\&. This option is ignored when tiered compilation is enabled; see the option
! \fB\-XX:+TieredCompilation\fR\&. The following example shows how to set the number of interpreted method invocations to 5,000:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CompileThreshold=5000\fR
!  
! .fi
! .if n \{\
  .RE
- .\}
- You can completely disable interpretation of Java methods before compilation by specifying the
- \fB\-Xcomp\fR
- option\&.
  .RE
! .PP
! \-XX:+DoEscapeAnalysis
! .RS 4
! Enables the use of escape analysis\&. This option is enabled by default\&. To disable the use of escape analysis, specify
! \fB\-XX:\-DoEscapeAnalysis\fR\&. Only the Java HotSpot Server VM supports this option\&.
! .RE
! .PP
! \-XX:InitialCodeCacheSize=\fIsize\fR
! .RS 4
! Sets the initial code cache size (in bytes)\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. The default value is set to 500 KB\&. The initial code cache size should be not less than the system\*(Aqs minimal memory page size\&. The following example shows how to set the initial code cache size to 32 KB:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:InitialCodeCacheSize=32k\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
! .PP
! \-XX:+Inline
! .RS 4
! Enables method inlining\&. This option is enabled by default to increase performance\&. To disable method inlining, specify
! \fB\-XX:\-Inline\fR\&.
! .RE
! .PP
! \-XX:InlineSmallCode=\fIsize\fR
! .RS 4
! Sets the maximum code size (in bytes) for compiled methods that should be inlined\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. Only compiled methods with the size smaller than the specified size will be inlined\&. By default, the maximum code size is set to 1000 bytes:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:InlineSmallCode=1000\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
! .PP
! \-XX:+LogCompilation
! .RS 4
  Enables logging of compilation activity to a file named
! \fBhotspot\&.log\fR
! in the current working directory\&. You can specify a different log file path and name using the
! \fB\-XX:LogFile\fR
! option\&.
! .sp
! By default, this option is disabled and compilation activity is not logged\&. The
! \fB\-XX:+LogCompilation\fR
! option has to be used together with the
! \fB\-XX:UnlockDiagnosticVMOptions\fR
! option that unlocks diagnostic JVM options\&.
! .sp
! You can enable verbose diagnostic output with a message printed to the console every time a method is compiled by using the
! \fB\-XX:+PrintCompilation\fR
! option\&.
! .RE
! .PP
! \-XX:MaxInlineSize=\fIsize\fR
! .RS 4
! Sets the maximum bytecode size (in bytes) of a method to be inlined\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. By default, the maximum bytecode size is set to 35 bytes:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:MaxInlineSize=35\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \-XX:MaxNodeLimit=\fInodes\fR
! .RS 4
! Sets the maximum number of nodes to be used during single method compilation\&. By default, the maximum number of nodes is set to 65,000:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:MaxNodeLimit=65000\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
  .RE
  .PP
! \-XX:MaxTrivialSize=\fIsize\fR
! .RS 4
! Sets the maximum bytecode size (in bytes) of a trivial method to be inlined\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. By default, the maximum bytecode size of a trivial method is set to 6 bytes:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:MaxTrivialSize=6\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \-XX:+OptimizeStringConcat
! .RS 4
! Enables the optimization of
! \fBString\fR
! concatenation operations\&. This option is enabled by default\&. To disable the optimization of
! \fBString\fR
! concatenation operations, specify
! \fB\-XX:\-OptimizeStringConcat\fR\&. Only the Java HotSpot Server VM supports this option\&.
  .RE
- .PP
- \-XX:+PrintAssembly
- .RS 4
- Enables printing of assembly code for bytecoded and native methods by using the external
- \fBdisassembler\&.so\fR
- library\&. This enables you to see the generated code, which may help you to diagnose performance issues\&.
- .sp
- By default, this option is disabled and assembly code is not printed\&. The
- \fB\-XX:+PrintAssembly\fR
- option has to be used together with the
- \fB\-XX:UnlockDiagnosticVMOptions\fR
- option that unlocks diagnostic JVM options\&.
  .RE
  .PP
! \-XX:+PrintCompilation
! .RS 4
! Enables verbose diagnostic output from the JVM by printing a message to the console every time a method is compiled\&. This enables you to see which methods actually get compiled\&. By default, this option is disabled and diagnostic output is not printed\&.
! .sp
! You can also log compilation activity to a file by using the
! \fB\-XX:+LogCompilation\fR
! option\&.
! .RE
  .PP
! \-XX:+PrintInlining
! .RS 4
! Enables printing of inlining decisions\&. This enables you to see which methods are getting inlined\&.
! .sp
! By default, this option is disabled and inlining information is not printed\&. The
! \fB\-XX:+PrintInlining\fR
! option has to be used together with the
! \fB\-XX:+UnlockDiagnosticVMOptions\fR
! option that unlocks diagnostic JVM options\&.
  .RE
- .PP
- \-XX:ReservedCodeCacheSize=\fIsize\fR
- .RS 4
- Sets the maximum code cache size (in bytes) for JIT\-compiled code\&. Append the letter
- \fBk\fR
- or
- \fBK\fR
- to indicate kilobytes,
- \fBm\fR
- or
- \fBM\fR
- to indicate megabytes,
- \fBg\fR
- or
- \fBG\fR
- to indicate gigabytes\&. The default maximum code cache size is 240 MB; if you disable tiered compilation with the option
- \fB\-XX:\-TieredCompilation\fR, then the default size is 48 MB\&. This option has a limit of 2 GB; otherwise, an error is generated\&. The maximum code cache size should not be less than the initial code cache size; see the option
- \fB\-XX:InitialCodeCacheSize\fR\&. This option is equivalent to
- \fB\-Xmaxjitcodesize\fR\&.
  .RE
  .PP
! \-XX:RTMAbortRatio=\fIabort_ratio\fR
! .RS 4
! The RTM abort ratio is specified as a percentage (%) of all executed RTM transactions\&. If a number of aborted transactions becomes greater than this ratio, then the compiled code will be deoptimized\&. This ratio is used when the
! \fB\-XX:+UseRTMDeopt\fR
! option is enabled\&. The default value of this option is 50\&. This means that the compiled code will be deoptimized if 50% of all transactions are aborted\&.
! .RE
  .PP
! \-XX:RTMRetryCount=\fInumber_of_retries\fR
! .RS 4
! RTM locking code will be retried, when it is aborted or busy, the number of times specified by this option before falling back to the normal locking mechanism\&. The default value for this option is 5\&. The
! \fB\-XX:UseRTMLocking\fR
! option must be enabled\&.
! .RE
  .PP
! \-XX:\-TieredCompilation
! .RS 4
! Disables the use of tiered compilation\&. By default, this option is enabled\&. Only the Java HotSpot Server VM supports this option\&.
  .RE
  .PP
! \-XX:+UseAES
! .RS 4
! Enables hardware\-based AES intrinsics for Intel, AMD, and SPARC hardware\&. Intel Westmere (2010 and newer), AMD Bulldozer (2011 and newer), and SPARC (T4 and newer) are the supported hardware\&. UseAES is used in conjunction with UseAESIntrinsics\&.
! .RE
  .PP
! \-XX:+UseAESIntrinsics
! .RS 4
! UseAES and UseAESIntrinsics flags are enabled by default and are supported only for Java HotSpot Server VM 32\-bit and 64\-bit\&. To disable hardware\-based AES intrinsics, specify
! \fB\-XX:\-UseAES \-XX:\-UseAESIntrinsics\fR\&. For example, to enable hardware AES, use the following flags:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:+UseAES \-XX:+UseAESIntrinsics\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! To support UseAES and UseAESIntrinsics flags for 32\-bit and 64\-bit use
! \fB\-server\fR
! option to choose Java HotSpot Server VM\&. These flags are not supported on Client VM\&.
! .RE
  .PP
! \-XX:+UseCodeCacheFlushing
! .RS 4
! Enables flushing of the code cache before shutting down the compiler\&. This option is enabled by default\&. To disable flushing of the code cache before shutting down the compiler, specify
! \fB\-XX:\-UseCodeCacheFlushing\fR\&.
! .RE
  .PP
! \-XX:+UseCondCardMark
! .RS 4
! Enables checking of whether the card is already marked before updating the card table\&. This option is disabled by default and should only be used on machines with multiple sockets, where it will increase performance of Java applications that rely heavily on concurrent operations\&. Only the Java HotSpot Server VM supports this option\&.
  .RE
- .PP
- \-XX:+UseRTMDeopt
- .RS 4
- Auto\-tunes RTM locking depending on the abort ratio\&. This ratio is specified by
- \fB\-XX:RTMAbortRatio\fR
- option\&. If the number of aborted transactions exceeds the abort ratio, then the method containing the lock will be deoptimized and recompiled with all locks as normal locks\&. This option is disabled by default\&. The
- \fB\-XX:+UseRTMLocking\fR
- option must be enabled\&.
  .RE
  .PP
! \-XX:+UseRTMLocking
! .RS 4
! Generate Restricted Transactional Memory (RTM) locking code for all inflated locks, with the normal locking mechanism as the fallback handler\&. This option is disabled by default\&. Options related to RTM are only available for the Java HotSpot Server VM on x86 CPUs that support Transactional Synchronization Extensions (TSX)\&.
! .sp
! RTM is part of Intel\*(Aqs TSX, which is an x86 instruction set extension and facilitates the creation of multithreaded applications\&. RTM introduces the new instructions
! \fBXBEGIN\fR,
! \fBXABORT\fR,
! \fBXEND\fR, and
! \fBXTEST\fR\&. The
! \fBXBEGIN\fR
! and
! \fBXEND\fR
! instructions enclose a set of instructions to run as a transaction\&. If no conflict is found when running the transaction, the memory and register modifications are committed together at the
! \fBXEND\fR
! instruction\&. The
! \fBXABORT\fR
! instruction can be used to explicitly abort a transaction and the
! \fBXEND\fR
! instruction to check if a set of instructions are being run in a transaction\&.
! .sp
! A lock on a transaction is inflated when another thread tries to access the same transaction, thereby blocking the thread that did not originally request access to the transaction\&. RTM requires that a fallback set of operations be specified in case a transaction aborts or fails\&. An RTM lock is a lock that has been delegated to the TSX\*(Aqs system\&.
! .sp
! RTM improves performance for highly contended locks with low conflict in a critical region (which is code that must not be accessed by more than one thread concurrently)\&. RTM also improves the performance of coarse\-grain locking, which typically does not perform well in multithreaded applications\&. (Coarse\-grain locking is the strategy of holding locks for long periods to minimize the overhead of taking and releasing locks, while fine\-grained locking is the strategy of trying to achieve maximum parallelism by locking only when necessary and unlocking as soon as possible\&.) Also, for lightly contended locks that are used by different threads, RTM can reduce false cache line sharing, also known as cache line ping\-pong\&. This occurs when multiple threads from different processors are accessing different resources, but the resources share the same cache line\&. As a result, the processors repeatedly invalidate the cache lines of other processors, which forces them to read from main memory instead of their cache\&.
  .RE
- .PP
- \-XX:+UseSHA
- .RS 4
- Enables hardware\-based intrinsics for SHA crypto hash functions for SPARC hardware\&.
- \fBUseSHA\fR
- is used in conjunction with the
- \fBUseSHA1Intrinsics\fR,
- \fBUseSHA256Intrinsics\fR, and
- \fBUseSHA512Intrinsics\fR
- options\&.
- .sp
- The
- \fBUseSHA\fR
- and
- \fBUseSHA*Intrinsics\fR
- flags are enabled by default, and are supported only for Java HotSpot Server VM 64\-bit on SPARC T4 and newer\&.
- .sp
- This feature is only applicable when using the
- \fBsun\&.security\&.provider\&.Sun\fR
- provider for SHA operations\&.
- .sp
- To disable all hardware\-based SHA intrinsics, specify
- \fB\-XX:\-UseSHA\fR\&. To disable only a particular SHA intrinsic, use the appropriate corresponding option\&. For example:
- \fB\-XX:\-UseSHA256Intrinsics\fR\&.
  .RE
  .PP
! \-XX:+UseSHA1Intrinsics
! .RS 4
! Enables intrinsics for SHA\-1 crypto hash function\&.
! .RE
  .PP
! \-XX:+UseSHA256Intrinsics
! .RS 4
! Enables intrinsics for SHA\-224 and SHA\-256 crypto hash functions\&.
! .RE
  .PP
! \-XX:+UseSHA512Intrinsics
! .RS 4
! Enables intrinsics for SHA\-384 and SHA\-512 crypto hash functions\&.
! .RE
  .PP
! \-XX:+UseSuperWord
! .RS 4
! Enables the transformation of scalar operations into superword operations\&. This option is enabled by default\&. To disable the transformation of scalar operations into superword operations, specify
! \fB\-XX:\-UseSuperWord\fR\&. Only the Java HotSpot Server VM supports this option\&.
! .RE
! .SS "Advanced Serviceability Options"
  .PP
! These options provide the ability to gather system information and perform extensive debugging\&.
  .PP
! \-XX:+ExtendedDTraceProbes
! .RS 4
! Enables additional
! \fBdtrace\fR
! tool probes that impact the performance\&. By default, this option is disabled and
! \fBdtrace\fR
! performs only standard probes\&.
! .RE
  .PP
! \-XX:+HeapDumpOnOutOfMemory
! .RS 4
! Enables the dumping of the Java heap to a file in the current directory by using the heap profiler (HPROF) when a
! \fBjava\&.lang\&.OutOfMemoryError\fR
! exception is thrown\&. You can explicitly set the heap dump file path and name using the
! \fB\-XX:HeapDumpPath\fR
! option\&. By default, this option is disabled and the heap is not dumped when an
! \fBOutOfMemoryError\fR
! exception is thrown\&.
! .RE
  .PP
! \-XX:HeapDumpPath=\fIpath\fR
! .RS 4
! Sets the path and file name for writing the heap dump provided by the heap profiler (HPROF) when the
! \fB\-XX:+HeapDumpOnOutOfMemoryError\fR
! option is set\&. By default, the file is created in the current working directory, and it is named
! \fBjava_pid\fR\fIpid\fR\fB\&.hprof\fR
! where
! \fIpid\fR
! is the identifier of the process that caused the error\&. The following example shows how to set the default file explicitly (\fB%p\fR
! represents the current process identificator):
! .sp
! .if n \{\
! .RS 4
! .\}
  .nf
! \fB\-XX:HeapDumpPath=\&./java_pid%p\&.hprof\fR
!  
  .fi
- .if n \{\
- .RE
- .\}
- The following example shows how to set the heap dump file to
- \fB/var/log/java/java_heapdump\&.hprof\fR:
- .sp
- .if n \{\
- .RS 4
- .\}
- .nf
- \fB\-XX:HeapDumpPath=/var/log/java/java_heapdump\&.hprof\fR
-  
- .fi
- .if n \{\
- .RE
- .\}
- .RE
  .PP
! \-XX:LogFile=\fIpath\fR
! .RS 4
! Sets the path and file name where log data is written\&. By default, the file is created in the current working directory, and it is named
! \fBhotspot\&.log\fR\&.
! .sp
! The following example shows how to set the log file to
! \fB/var/log/java/hotspot\&.log\fR:
! .sp
! .if n \{\
! .RS 4
! .\}
  .nf
! \fB\-XX:LogFile=/var/log/java/hotspot\&.log\fR
!  
  .fi
- .if n \{\
- .RE
- .\}
- .RE
- .PP
- \-XX:+PrintClassHistogram
- .RS 4
- Enables printing of a class instance histogram after a
- \fBControl+C\fR
- event (\fBSIGTERM\fR)\&. By default, this option is disabled\&.
- .sp
- Setting this option is equivalent to running the
- \fBjmap \-histo\fR
- command, or the
- \fBjcmd \fR\fIpid\fR\fB GC\&.class_histogram\fR
- command, where
- \fIpid\fR
- is the current Java process identifier\&.
- .RE
- .PP
- \-XX:+PrintConcurrentLocks
- .RS 4
- Enables printing of locks after a event\&. By default, this option is disabled\&.
- .sp
- Enables printing of
- \fBjava\&.util\&.concurrent\fR
- locks after a
- \fBControl+C\fR
- event (\fBSIGTERM\fR)\&. By default, this option is disabled\&.
- .sp
- Setting this option is equivalent to running the
- \fBjstack \-l\fR
- command or the
- \fBjcmd \fR\fIpid\fR\fB Thread\&.print \-l\fR
- command, where
- \fIpid\fR
- is the current Java process identifier\&.
- .RE
  .PP
! \-XX:+UnlockDiagnosticVMOptions
! .RS 4
! Unlocks the options intended for diagnosing the JVM\&. By default, this option is disabled and diagnostic options are not available\&.
! .RE
! .SS "Advanced Garbage Collection Options"
! .PP
! These options control how garbage collection (GC) is performed by the Java HotSpot VM\&.
! .PP
! \-XX:+AggressiveHeap
! .RS 4
! Enables Java heap optimization\&. This sets various parameters to be optimal for long\-running jobs with intensive memory allocation, based on the configuration of the computer (RAM and CPU)\&. By default, the option is disabled and the heap is not optimized\&.
! .RE
! .PP
! \-XX:+AlwaysPreTouch
! .RS 4
! Enables touching of every page on the Java heap during JVM initialization\&. This gets all pages into the memory before entering the
! \fBmain()\fR
! method\&. The option can be used in testing to simulate a long\-running system with all virtual memory mapped to physical memory\&. By default, this option is disabled and all pages are committed as JVM heap space fills\&.
! .RE
! .PP
! \-XX:+CMSClassUnloadingEnabled
! .RS 4
! Enables class unloading when using the concurrent mark\-sweep (CMS) garbage collector\&. This option is enabled by default\&. To disable class unloading for the CMS garbage collector, specify
! \fB\-XX:\-CMSClassUnloadingEnabled\fR\&.
! .RE
! .PP
! \-XX:CMSExpAvgFactor=\fIpercent\fR
! .RS 4
! Sets the percentage of time (0 to 100) used to weight the current sample when computing exponential averages for the concurrent collection statistics\&. By default, the exponential averages factor is set to 25%\&. The following example shows how to set the factor to 15%:
! .sp
! .if n \{\
! .RS 4
! .\}
  .nf
! \fB\-XX:CMSExpAvgFactor=15\fR
!  
  .fi
- .if n \{\
- .RE
- .\}
  .RE
  .PP
! \-XX:CMSInitiatingOccupancyFraction=\fIpercent\fR
! .RS 4
! Sets the percentage of the old generation occupancy (0 to 100) at which to start a CMS collection cycle\&. The default value is set to \-1\&. Any negative value (including the default) implies that
! \fB\-XX:CMSTriggerRatio\fR
! is used to define the value of the initiating occupancy fraction\&.
! .sp
! The following example shows how to set the occupancy fraction to 20%:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CMSInitiatingOccupancyFraction=20\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \-XX:+CMSScavengeBeforeRemark
! .RS 4
! Enables scavenging attempts before the CMS remark step\&. By default, this option is disabled\&.
! .RE
  .PP
! \-XX:CMSTriggerRatio=\fIpercent\fR
! .RS 4
! Sets the percentage (0 to 100) of the value specified by
! \fB\-XX:MinHeapFreeRatio\fR
! that is allocated before a CMS collection cycle commences\&. The default value is set to 80%\&.
! .sp
! The following example shows how to set the occupancy fraction to 75%:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:CMSTriggerRatio=75\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \-XX:ConcGCThreads=\fIthreads\fR
! .RS 4
! Sets the number of threads used for concurrent GC\&. The default value depends on the number of CPUs available to the JVM\&.
! .sp
! For example, to set the number of threads for concurrent GC to 2, specify the following option:
! .sp
! .if n \{\
! .RS 4
! .\}
  .nf
! \fB\-XX:ConcGCThreads=2\fR
!  
  .fi
- .if n \{\
- .RE
- .\}
- .RE
  .PP
! \-XX:+DisableExplicitGC
! .RS 4
! Enables the option that disables processing of calls to
! \fBSystem\&.gc()\fR\&. This option is disabled by default, meaning that calls to
! \fBSystem\&.gc()\fR
! are processed\&. If processing of calls to
! \fBSystem\&.gc()\fR
! is disabled, the JVM still performs GC when necessary\&.
! .RE
  .PP
! \-XX:+ExplicitGCInvokesConcurrent
! .RS 4
! Enables invoking of concurrent GC by using the
! \fBSystem\&.gc()\fR
! request\&. This option is disabled by default and can be enabled only together with the
! \fB\-XX:+UseConcMarkSweepGC\fR
! option\&.
! .RE
  .PP
! \-XX:+ExplicitGCInvokesConcurrentAndUnloadsClasses
! .RS 4
! Enables invoking of concurrent GC by using the
! \fBSystem\&.gc()\fR
! request and unloading of classes during the concurrent GC cycle\&. This option is disabled by default and can be enabled only together with the
! \fB\-XX:+UseConcMarkSweepGC\fR
! option\&.
! .RE
  .PP
! \-XX:G1HeapRegionSize=\fIsize\fR
! .RS 4
! Sets the size of the regions into which the Java heap is subdivided when using the garbage\-first (G1) collector\&. The value can be between 1 MB and 32 MB\&. The default region size is determined ergonomically based on the heap size\&.
! .sp
! The following example shows how to set the size of the subdivisions to 16 MB:
! .sp
! .if n \{\
  .RS 4
! .\}
! .nf
! \fB\-XX:G1HeapRegionSize=16m\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \-XX:+G1PrintHeapRegions
! .RS 4
! Enables the printing of information about which regions are allocated and which are reclaimed by the G1 collector\&. By default, this option is disabled\&.
  .RE
  .PP
! \-XX:G1ReservePercent=\fIpercent\fR
! .RS 4
! Sets the percentage of the heap (0 to 50) that is reserved as a false ceiling to reduce the possibility of promotion failure for the G1 collector\&. By default, this option is set to 10%\&.
! .sp
! The following example shows how to set the reserved heap to 20%:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:G1ReservePercent=20\fR
!  
! .fi
! .if n \{\
  .RE
! .\}
! .RE
! .PP
! \-XX:InitialHeapSize=\fIsize\fR
  .RS 4
! Sets the initial size (in bytes) of the memory allocation pool\&. This value must be either 0, or a multiple of 1024 and greater than 1 MB\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. The default value is chosen at runtime based on system configuration\&. See the section "Ergonomics" in
! \fIJava SE HotSpot Virtual Machine Garbage Collection Tuning Guide\fR
! at http://docs\&.oracle\&.com/javase/8/docs/technotes/guides/vm/gctuning/index\&.html\&.
! .sp
! The following examples show how to set the size of allocated memory to 6 MB using various units:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:InitialHeapSize=6291456\fR
! \fB\-XX:InitialHeapSize=6144k\fR
! \fB\-XX:InitialHeapSize=6m\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! If you set this option to 0, then the initial size will be set as the sum of the sizes allocated for the old generation and the young generation\&. The size of the heap for the young generation can be set using the
! \fB\-XX:NewSize\fR
! option\&.
! .RE
  .PP
! \-XX:InitialSurvivorRatio=\fIratio\fR
! .RS 4
! Sets the initial survivor space ratio used by the throughput garbage collector (which is enabled by the
! \fB\-XX:+UseParallelGC\fR
! and/or \-\fBXX:+UseParallelOldGC\fR
! options)\&. Adaptive sizing is enabled by default with the throughput garbage collector by using the
! \fB\-XX:+UseParallelGC\fR
! and
! \fB\-XX:+UseParallelOldGC\fR
! options, and survivor space is resized according to the application behavior, starting with the initial value\&. If adaptive sizing is disabled (using the
! \fB\-XX:\-UseAdaptiveSizePolicy\fR
! option), then the
! \fB\-XX:SurvivorRatio\fR
! option should be used to set the size of the survivor space for the entire execution of the application\&.
! .sp
! The following formula can be used to calculate the initial size of survivor space (S) based on the size of the young generation (Y), and the initial survivor space ratio (R):
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fBS=Y/(R+2)\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! The 2 in the equation denotes two survivor spaces\&. The larger the value specified as the initial survivor space ratio, the smaller the initial survivor space size\&.
! .sp
! By default, the initial survivor space ratio is set to 8\&. If the default value for the young generation space size is used (2 MB), the initial size of the survivor space will be 0\&.2 MB\&.
! .sp
! The following example shows how to set the initial survivor space ratio to 4:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:InitialSurvivorRatio=4\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
  .RE
  .PP
! \-XX:InitiatingHeapOccupancyPercent=\fIpercent\fR
! .RS 4
! Sets the percentage of the heap occupancy (0 to 100) at which to start a concurrent GC cycle\&. It is used by garbage collectors that trigger a concurrent GC cycle based on the occupancy of the entire heap, not just one of the generations (for example, the G1 garbage collector)\&.
! .sp
! By default, the initiating value is set to 45%\&. A value of 0 implies nonstop GC cycles\&. The following example shows how to set the initiating heap occupancy to 75%:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:InitiatingHeapOccupancyPercent=75\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
  .RE
! .PP
! \-XX:MaxGCPauseMillis=\fItime\fR
! .RS 4
! Sets a target for the maximum GC pause time (in milliseconds)\&. This is a soft goal, and the JVM will make its best effort to achieve it\&. By default, there is no maximum pause time value\&.
! .sp
! The following example shows how to set the maximum target pause time to 500 ms:
! .sp
! .if n \{\
  .RS 4
! .\}
! .nf
! \fB\-XX:MaxGCPauseMillis=500\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \-XX:MaxHeapSize=\fIsize\fR
! .RS 4
! Sets the maximum size (in byes) of the memory allocation pool\&. This value must be a multiple of 1024 and greater than 2 MB\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. The default value is chosen at runtime based on system configuration\&. For server deployments,
! \fB\-XX:InitialHeapSize\fR
! and
! \fB\-XX:MaxHeapSize\fR
! are often set to the same value\&. See the section "Ergonomics" in
! \fIJava SE HotSpot Virtual Machine Garbage Collection Tuning Guide\fR
! at http://docs\&.oracle\&.com/javase/8/docs/technotes/guides/vm/gctuning/index\&.html\&.
! .sp
! The following examples show how to set the maximum allowed size of allocated memory to 80 MB using various units:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:MaxHeapSize=83886080\fR
! \fB\-XX:MaxHeapSize=81920k\fR
! \fB\-XX:MaxHeapSize=80m\fR
!  
! .fi
! .if n \{\
  .RE
- .\}
- On Oracle Solaris 7 and Oracle Solaris 8 SPARC platforms, the upper limit for this value is approximately 4,000 MB minus overhead amounts\&. On Oracle Solaris 2\&.6 and x86 platforms, the upper limit is approximately 2,000 MB minus overhead amounts\&. On Linux platforms, the upper limit is approximately 2,000 MB minus overhead amounts\&.
- .sp
- The
- \fB\-XX:MaxHeapSize\fR
- option is equivalent to
- \fB\-Xmx\fR\&.
  .RE
! .PP
! \-XX:MaxHeapFreeRatio=\fIpercent\fR
! .RS 4
! Sets the maximum allowed percentage of free heap space (0 to 100) after a GC event\&. If free heap space expands above this value, then the heap will be shrunk\&. By default, this value is set to 70%\&.
! .sp
! The following example shows how to set the maximum free heap ratio to 75%:
! .sp
! .if n \{\
  .RS 4
! .\}
! .nf
! \fB\-XX:MaxHeapFreeRatio=75\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
  .RE
  .PP
! \-XX:MaxMetaspaceSize=\fIsize\fR
! .RS 4
! Sets the maximum amount of native memory that can be allocated for class metadata\&. By default, the size is not limited\&. The amount of metadata for an application depends on the application itself, other running applications, and the amount of memory available on the system\&.
! .sp
! The following example shows how to set the maximum class metadata size to 256 MB:
! .sp
! .if n \{\
! .RS 4
! .\}
  .nf
! \fB\-XX:MaxMetaspaceSize=256m\fR
!  
  .fi
- .if n \{\
- .RE
- .\}
  .RE
  .PP
! \-XX:MaxNewSize=\fIsize\fR
  .RS 4
! Sets the maximum size (in bytes) of the heap for the young generation (nursery)\&. The default value is set ergonomically\&.
! .RE
  .PP
! \-XX:MaxTenuringThreshold=\fIthreshold\fR
! .RS 4
! Sets the maximum tenuring threshold for use in adaptive GC sizing\&. The largest value is 15\&. The default value is 15 for the parallel (throughput) collector, and 6 for the CMS collector\&.
! .sp
! The following example shows how to set the maximum tenuring threshold to 10:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:MaxTenuringThreshold=10\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
  .RE
  .PP
! \-XX:MetaspaceSize=\fIsize\fR
! .RS 4
! Sets the size of the allocated class metadata space that will trigger a garbage collection the first time it is exceeded\&. This threshold for a garbage collection is increased or decreased depending on the amount of metadata used\&. The default size depends on the platform\&.
  .RE
! .PP
! \-XX:MinHeapFreeRatio=\fIpercent\fR
! .RS 4
! Sets the minimum allowed percentage of free heap space (0 to 100) after a GC event\&. If free heap space falls below this value, then the heap will be expanded\&. By default, this value is set to 40%\&.
! .sp
! The following example shows how to set the minimum free heap ratio to 25%:
! .sp
! .if n \{\
  .RS 4
! .\}
! .nf
! \fB\-XX:MinHeapFreeRatio=25\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \-XX:NewRatio=\fIratio\fR
! .RS 4
! Sets the ratio between young and old generation sizes\&. By default, this option is set to 2\&. The following example shows how to set the young/old ratio to 1:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:NewRatio=1\fR
!  
! .fi
! .if n \{\
  .RE
- .\}
  .RE
  .PP
! \-XX:NewSize=\fIsize\fR
! .RS 4
! Sets the initial size (in bytes) of the heap for the young generation (nursery)\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&.
! .sp
! The young generation region of the heap is used for new objects\&. GC is performed in this region more often than in other regions\&. If the size for the young generation is too low, then a large number of minor GCs will be performed\&. If the size is too high, then only full GCs will be performed, which can take a long time to complete\&. Oracle recommends that you keep the size for the young generation between a half and a quarter of the overall heap size\&.
! .sp
! The following examples show how to set the initial size of young generation to 256 MB using various units:
! .sp
! .if n \{\
! .RS 4
! .\}
  .nf
! \fB\-XX:NewSize=256m\fR
! \fB\-XX:NewSize=262144k\fR
! \fB\-XX:NewSize=268435456\fR
!  
  .fi
- .if n \{\
- .RE
- .\}
- The
- \fB\-XX:NewSize\fR
- option is equivalent to
- \fB\-Xmn\fR\&.
- .RE
  .PP
! \-XX:ParallelGCThreads=\fIthreads\fR
! .RS 4
! Sets the number of threads used for parallel garbage collection in the young and old generations\&. The default value depends on the number of CPUs available to the JVM\&.
! .sp
! For example, to set the number of threads for parallel GC to 2, specify the following option:
! .sp
! .if n \{\
! .RS 4
! .\}
  .nf
! \fB\-XX:ParallelGCThreads=2\fR
!  
  .fi
- .if n \{\
- .RE
- .\}
- .RE
  .PP
! \-XX:+ParallelRefProcEnabled
! .RS 4
! Enables parallel reference processing\&. By default, this option is disabled\&.
! .RE
  .PP
! \-XX:+PrintAdaptiveSizePolicy
! .RS 4
! Enables printing of information about adaptive generation sizing\&. By default, this option is disabled\&.
! .RE
  .PP
! \-XX:+PrintGC
! .RS 4
! Enables printing of messages at every GC\&. By default, this option is disabled\&.
  .RE
  .PP
! \-XX:+PrintGCApplicationConcurrentTime
! .RS 4
! Enables printing of how much time elapsed since the last pause (for example, a GC pause)\&. By default, this option is disabled\&.
! .RE
  .PP
! \-XX:+PrintGCApplicationStoppedTime
! .RS 4
! Enables printing of how much time the pause (for example, a GC pause) lasted\&. By default, this option is disabled\&.
  .RE
  .PP
! \-XX:+PrintGCDateStamps
! .RS 4
! Enables printing of a date stamp at every GC\&. By default, this option is disabled\&.
! .RE
  .PP
! \-XX:+PrintGCDetails
! .RS 4
! Enables printing of detailed messages at every GC\&. By default, this option is disabled\&.
! .RE
  .PP
! \-XX:+PrintGCTaskTimeStamps
! .RS 4
! Enables printing of time stamps for every individual GC worker thread task\&. By default, this option is disabled\&.
! .RE
! .PP
! \-XX:+PrintGCTimeStamps
! .RS 4
! Enables printing of time stamps at every GC\&. By default, this option is disabled\&.
! .RE
! .PP
! \-XX:+PrintStringDeduplicationStatistics
! .RS 4
! Prints detailed deduplication statistics\&. By default, this option is disabled\&. See the
! \fB\-XX:+UseStringDeduplication\fR
! option\&.
! .RE
! .PP
! \-XX:+PrintTenuringDistribution
! .RS 4
! Enables printing of tenuring age information\&. The following is an example of the output:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fBDesired survivor size 48286924 bytes, new threshold 10 (max 10)\fR
! \fB\- age 1: 28992024 bytes, 28992024 total\fR
! \fB\- age 2: 1366864 bytes, 30358888 total\fR
! \fB\- age 3: 1425912 bytes, 31784800 total\fR
! \fB\&.\&.\&.\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! Age 1 objects are the youngest survivors (they were created after the previous scavenge, survived the latest scavenge, and moved from eden to survivor space)\&. Age 2 objects have survived two scavenges (during the second scavenge they were copied from one survivor space to the next)\&. And so on\&.
! .sp
! In the preceding example, 28 992 024 bytes survived one scavenge and were copied from eden to survivor space, 1 366 864 bytes are occupied by age 2 objects, etc\&. The third value in each row is the cumulative size of objects of age n or less\&.
! .sp
! By default, this option is disabled\&.
! .RE
  .PP
! \-XX:+ScavengeBeforeFullGC
! .RS 4
! Enables GC of the young generation before each full GC\&. This option is enabled by default\&. Oracle recommends that you
! \fIdo not\fR
! disable it, because scavenging the young generation before a full GC can reduce the number of objects reachable from the old generation space into the young generation space\&. To disable GC of the young generation before each full GC, specify
! \fB\-XX:\-ScavengeBeforeFullGC\fR\&.
! .RE
  .PP
! \-XX:SoftRefLRUPolicyMSPerMB=\fItime\fR
  .RS 4
! Sets the amount of time (in milliseconds) a softly reachable object is kept active on the heap after the last time it was referenced\&. The default value is one second of lifetime per free megabyte in the heap\&. The
! \fB\-XX:SoftRefLRUPolicyMSPerMB\fR
! option accepts integer values representing milliseconds per one megabyte of the current heap size (for Java HotSpot Client VM) or the maximum possible heap size (for Java HotSpot Server VM)\&. This difference means that the Client VM tends to flush soft references rather than grow the heap, whereas the Server VM tends to grow the heap rather than flush soft references\&. In the latter case, the value of the
! \fB\-Xmx\fR
! option has a significant effect on how quickly soft references are garbage collected\&.
! .sp
! The following example shows how to set the value to 2\&.5 seconds:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:SoftRefLRUPolicyMSPerMB=2500\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \-XX:StringDeduplicationAgeThreshold=\fIthreshold\fR
! .RS 4
! \fBString\fR
! objects reaching the specified age are considered candidates for deduplication\&. An object\*(Aqs age is a measure of how many times it has survived garbage collection\&. This is sometimes referred to as tenuring; see the
! \fB\-XX:+PrintTenuringDistribution\fR
! option\&. Note that
! \fBString\fR
! objects that are promoted to an old heap region before this age has been reached are always considered candidates for deduplication\&. The default value for this option is
! \fB3\fR\&. See the
! \fB\-XX:+UseStringDeduplication\fR
! option\&.
  .RE
  .PP
! \-XX:SurvivorRatio=\fIratio\fR
! .RS 4
! Sets the ratio between eden space size and survivor space size\&. By default, this option is set to 8\&. The following example shows how to set the eden/survivor space ratio to 4:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:SurvivorRatio=4\fR
!  
! .fi
! .if n \{\
  .RE
- .\}
  .RE
! .PP
! \-XX:TargetSurvivorRatio=\fIpercent\fR
  .RS 4
- Sets the desired percentage of survivor space (0 to 100) used after young garbage collection\&. By default, this option is set to 50%\&.
- .sp
- The following example shows how to set the target survivor space ratio to 30%:
- .sp
- .if n \{\
- .RS 4
- .\}
- .nf
- \fB\-XX:TargetSurvivorRatio=30\fR
-  
- .fi
- .if n \{\
- .RE
- .\}
- .RE
  .PP
! \-XX:TLABSize=\fIsize\fR
! .RS 4
! Sets the initial size (in bytes) of a thread\-local allocation buffer (TLAB)\&. Append the letter
! \fBk\fR
! or
! \fBK\fR
! to indicate kilobytes,
! \fBm\fR
! or
! \fBM\fR
! to indicate megabytes,
! \fBg\fR
! or
! \fBG\fR
! to indicate gigabytes\&. If this option is set to 0, then the JVM chooses the initial size automatically\&.
! .sp
! The following example shows how to set the initial TLAB size to 512 KB:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB\-XX:TLABSize=512k\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \-XX:+UseAdaptiveSizePolicy
! .RS 4
! Enables the use of adaptive generation sizing\&. This option is enabled by default\&. To disable adaptive generation sizing, specify
! \fB\-XX:\-UseAdaptiveSizePolicy\fR
! and set the size of the memory allocation pool explicitly (see the
! \fB\-XX:SurvivorRatio\fR
! option)\&.
  .RE
  .PP
! \-XX:+UseCMSInitiatingOccupancyOnly
! .RS 4
! Enables the use of the occupancy value as the only criterion for initiating the CMS collector\&. By default, this option is disabled and other criteria may be used\&.
! .RE
  .PP
! \-XX:+UseConcMarkSweepGC
! .RS 4
! Enables the use of the CMS garbage collector for the old generation\&. Oracle recommends that you use the CMS garbage collector when application latency requirements cannot be met by the throughput (\fB\-XX:+UseParallelGC\fR) garbage collector\&. The G1 garbage collector (\fB\-XX:+UseG1GC\fR) is another alternative\&.
! .sp
! By default, this option is disabled and the collector is chosen automatically based on the configuration of the machine and type of the JVM\&. When this option is enabled, the
! \fB\-XX:+UseParNewGC\fR
! option is automatically set and you should not disable it, because the following combination of options has been deprecated in JDK 8:
! \fB\-XX:+UseConcMarkSweepGC \-XX:\-UseParNewGC\fR\&.
  .RE
- .PP
- \-XX:+UseG1GC
- .RS 4
- Enables the use of the garbage\-first (G1) garbage collector\&. It is a server\-style garbage collector, targeted for multiprocessor machines with a large amount of RAM\&. It meets GC pause time goals with high probability, while maintaining good throughput\&. The G1 collector is recommended for applications requiring large heaps (sizes of around 6 GB or larger) with limited GC latency requirements (stable and predictable pause time below 0\&.5 seconds)\&.
- .sp
- By default, this option is disabled and the collector is chosen automatically based on the configuration of the machine and type of the JVM\&.
  .RE
! .PP
! \-XX:+UseGCOverheadLimit
  .RS 4
! Enables the use of a policy that limits the proportion of time spent by the JVM on GC before an
! \fBOutOfMemoryError\fR
! exception is thrown\&. This option is enabled, by default and the parallel GC will throw an
! \fBOutOfMemoryError\fR
! if more than 98% of the total time is spent on garbage collection and less than 2% of the heap is recovered\&. When the heap is small, this feature can be used to prevent applications from running for long periods of time with little or no progress\&. To disable this option, specify
! \fB\-XX:\-UseGCOverheadLimit\fR\&.
! .RE
  .PP
! \-XX:+UseNUMA
! .RS 4
! Enables performance optimization of an application on a machine with nonuniform memory architecture (NUMA) by increasing the application\*(Aqs use of lower latency memory\&. By default, this option is disabled and no optimization for NUMA is made\&. The option is only available when the parallel garbage collector is used (\fB\-XX:+UseParallelGC\fR)\&.
  .RE
  .PP
! \-XX:+UseParallelGC
! .RS 4
! Enables the use of the parallel scavenge garbage collector (also known as the throughput collector) to improve the performance of your application by leveraging multiple processors\&.
! .sp
! By default, this option is disabled and the collector is chosen automatically based on the configuration of the machine and type of the JVM\&. If it is enabled, then the
! \fB\-XX:+UseParallelOldGC\fR
! option is automatically enabled, unless you explicitly disable it\&.
  .RE
! .PP
! \-XX:+UseParallelOldGC
  .RS 4
! Enables the use of the parallel garbage collector for full GCs\&. By default, this option is disabled\&. Enabling it automatically enables the
! \fB\-XX:+UseParallelGC\fR
! option\&.
! .RE
  .PP
! \-XX:+UseParNewGC
! .RS 4
! Enables the use of parallel threads for collection in the young generation\&. By default, this option is disabled\&. It is automatically enabled when you set the
! \fB\-XX:+UseConcMarkSweepGC\fR
! option\&. Using the
! \fB\-XX:+UseParNewGC\fR
! option without the
! \fB\-XX:+UseConcMarkSweepGC\fR
! option was deprecated in JDK 8\&.
  .RE
  .PP
! \-XX:+UseSerialGC
! .RS 4
! Enables the use of the serial garbage collector\&. This is generally the best choice for small and simple applications that do not require any special functionality from garbage collection\&. By default, this option is disabled and the collector is chosen automatically based on the configuration of the machine and type of the JVM\&.
  .RE
- .PP
- \-XX:+UseSHM
- .RS 4
- On Linux, enables the JVM to use shared memory to setup large pages\&.
- .sp
- For more information, see "Large Pages"\&.
  .RE
  .PP
! \-XX:+UseStringDeduplication
! .RS 4
! Enables string deduplication\&. By default, this option is disabled\&. To use this option, you must enable the garbage\-first (G1) garbage collector\&. See the
! \fB\-XX:+UseG1GC\fR
! option\&.
! .sp
! \fIString deduplication\fR
! reduces the memory footprint of
! \fBString\fR
! objects on the Java heap by taking advantage of the fact that many
! \fBString\fR
! objects are identical\&. Instead of each
! \fBString\fR
! object pointing to its own character array, identical
! \fBString\fR
! objects can point to and share the same character array\&.
! .RE
  .PP
! \-XX:+UseTLAB
! .RS 4
! Enables the use of thread\-local allocation blocks (TLABs) in the young generation space\&. This option is enabled by default\&. To disable the use of TLABs, specify
! \fB\-XX:\-UseTLAB\fR\&.
  .RE
- .SS "Deprecated and Removed Options"
  .PP
! These options were included in the previous release, but have since been considered unnecessary\&.
  .PP
! \-Xincgc
! .RS 4
! Enables incremental garbage collection\&. This option was deprecated in JDK 8 with no replacement\&.
! .RE
  .PP
! \-Xrun\fIlibname\fR
! .RS 4
! Loads the specified debugging/profiling library\&. This option was superseded by the
! \fB\-agentlib\fR
! option\&.
! .RE
  .PP
! \-XX:CMSIncrementalDutyCycle=\fIpercent\fR
! .RS 4
! Sets the percentage of time (0 to 100) between minor collections that the concurrent collector is allowed to run\&. This option was deprecated in JDK 8 with no replacement, following the deprecation of the
! \fB\-XX:+CMSIncrementalMode\fR
! option\&.
! .RE
  .PP
! \-XX:CMSIncrementalDutyCycleMin=\fIpercent\fR
! .RS 4
! Sets the percentage of time (0 to 100) between minor collections that is the lower bound for the duty cycle when
! \fB\-XX:+CMSIncrementalPacing\fR
! is enabled\&. This option was deprecated in JDK 8 with no replacement, following the deprecation of the
! \fB\-XX:+CMSIncrementalMode\fR
! option\&.
  .RE
  .PP
! \-XX:+CMSIncrementalMode
! .RS 4
! Enables the incremental mode for the CMS collector\&. This option was deprecated in JDK 8 with no replacement, along with other options that start with
! \fBCMSIncremental\fR\&.
  .RE
  .PP
! \-XX:CMSIncrementalOffset=\fIpercent\fR
! .RS 4
! Sets the percentage of time (0 to 100) by which the incremental mode duty cycle is shifted to the right within the period between minor collections\&. This option was deprecated in JDK 8 with no replacement, following the deprecation of the
! \fB\-XX:+CMSIncrementalMode\fR
! option\&.
! .RE
  .PP
! \-XX:+CMSIncrementalPacing
! .RS 4
! Enables automatic adjustment of the incremental mode duty cycle based on statistics collected while the JVM is running\&. This option was deprecated in JDK 8 with no replacement, following the deprecation of the
! \fB\-XX:+CMSIncrementalMode\fR
! option\&.
! .RE
  .PP
! \-XX:CMSIncrementalSafetyFactor=\fIpercent\fR
! .RS 4
! Sets the percentage of time (0 to 100) used to add conservatism when computing the duty cycle\&. This option was deprecated in JDK 8 with no replacement, following the deprecation of the
! \fB\-XX:+CMSIncrementalMode\fR
! option\&.
  .RE
  .PP
! \-XX:CMSInitiatingPermOccupancyFraction=\fIpercent\fR
! .RS 4
! Sets the percentage of the permanent generation occupancy (0 to 100) at which to start a GC\&. This option was deprecated in JDK 8 with no replacement\&.
! .RE
  .PP
! \-XX:MaxPermSize=\fIsize\fR
! .RS 4
! Sets the maximum permanent generation space size (in bytes)\&. This option was deprecated in JDK 8, and superseded by the
! \fB\-XX:MaxMetaspaceSize\fR
! option\&.
! .RE
  .PP
! \-XX:PermSize=\fIsize\fR
! .RS 4
! Sets the space (in bytes) allocated to the permanent generation that triggers a garbage collection if it is exceeded\&. This option was deprecated un JDK 8, and superseded by the
! \fB\-XX:MetaspaceSize\fR
! option\&.
! .RE
  .PP
! \-XX:+UseSplitVerifier
! .RS 4
! Enables splitting of the verification process\&. By default, this option was enabled in the previous releases, and verification was split into two phases: type referencing (performed by the compiler) and type checking (performed by the JVM runtime)\&. This option was deprecated in JDK 8, and verification is now split by default without a way to disable it\&.
! .RE
  .PP
! \-XX:+UseStringCache
! .RS 4
! Enables caching of commonly allocated strings\&. This option was removed from JDK 8 with no replacement\&.
  .RE
! .SH "PERFORMANCE TUNING EXAMPLES"
! .PP
! The following examples show how to use experimental tuning flags to either optimize throughput or to provide lower response time\&.
  .PP
! \fBExample 1 \fRTuning for Higher Throughput
! .RS 4
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fBjava \-d64 \-server \-XX:+UseLargePages \-Xmn10g  \-Xms26g \-Xmx26g\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
  .PP
! \fBExample 2 \fRTuning for Lower Response Time
! .RS 4
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fBjava \-d64 \-XX:+UseG1GC \-Xms26g Xmx26g \-XX:MaxGCPauseMillis=500 \-XX:+PrintGCTimeStamp\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
  .RE
! .SH "LARGE PAGES"
  .PP
! Also known as huge pages, large pages are memory pages that are significantly larger than the standard memory page size (which varies depending on the processor and operating system)\&. Large pages optimize processor Translation\-Lookaside Buffers\&.
! .PP
! A Translation\-Lookaside Buffer (TLB) is a page translation cache that holds the most\-recently used virtual\-to\-physical address translations\&. TLB is a scarce system resource\&. A TLB miss can be costly as the processor must then read from the hierarchical page table, which may require multiple memory accesses\&. By using a larger memory page size, a single TLB entry can represent a larger memory range\&. There will be less pressure on TLB, and memory\-intensive applications may have better performance\&.
! .PP
! However, large pages page memory can negatively affect system performance\&. For example, when a large mount of memory is pinned by an application, it may create a shortage of regular memory and cause excessive paging in other applications and slow down the entire system\&. Also, a system that has been up for a long time could produce excessive fragmentation, which could make it impossible to reserve enough large page memory\&. When this happens, either the OS or JVM reverts to using regular pages\&.
! .SS "Large Pages Support"
! .PP
! Solaris and Linux support large pages\&.
! .sp
! .it 1 an-trap
! .nr an-no-space-flag 1
! .nr an-break-flag 1
! .br
! .ps +1
! \fBSolaris\fR
! .RS 4
  .PP
! Solaris 9 and later include Multiple Page Size Support (MPSS); no additional configuration is necessary\&. See http://www\&.oracle\&.com/technetwork/server\-storage/solaris10/overview/solaris9\-features\-scalability\-135663\&.html\&.
  .RE
! .sp
! .it 1 an-trap
! .nr an-no-space-flag 1
! .nr an-break-flag 1
! .br
! .ps +1
! \fBLinux\fR
! .RS 4
  .PP
! The 2\&.6 kernel supports large pages\&. Some vendors have backported the code to their 2\&.4\-based releases\&. To check if your system can support large page memory, try the following:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB# cat /proc/meminfo | grep Huge\fR
! \fBHugePages_Total: 0\fR
! \fBHugePages_Free: 0\fR
! \fBHugepagesize: 2048 kB\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .PP
! If the output shows the three "Huge" variables, then your system can support large page memory but it needs to be configured\&. If the command prints nothing, then your system does not support large pages\&. To configure the system to use large page memory, login as
! \fBroot\fR, and then follow these steps:
! .sp
! .RS 4
! .ie n \{\
! \h'-04' 1.\h'+01'\c
! .\}
! .el \{\
! .sp -1
! .IP "  1." 4.2
! .\}
! If you are using the option
! \fB\-XX:+UseSHM\fR
! (instead of
! \fB\-XX:+UseHugeTLBFS\fR), then increase the
! \fBSHMMAX\fR
! value\&. It must be larger than the Java heap size\&. On a system with 4 GB of physical RAM (or less), the following will make all the memory sharable:
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB# echo 4294967295 > /proc/sys/kernel/shmmax\fR
!  
! .fi
! .if n \{\
! .RE
! .\}
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04' 2.\h'+01'\c
! .\}
! .el \{\
! .sp -1
! .IP "  2." 4.2
! .\}
! If you are using the option
! \fB\-XX:+UseSHM\fR
! or
! \fB\-XX:+UseHugeTLBFS\fR, then specify the number of large pages\&. In the following example, 3 GB of a 4 GB system are reserved for large pages (assuming a large page size of 2048kB, then 3 GB = 3 * 1024 MB = 3072 MB = 3072 * 1024 kB = 3145728 kB and 3145728 kB / 2048 kB = 1536):
! .sp
! .if n \{\
! .RS 4
! .\}
! .nf
! \fB# echo 1536 > /proc/sys/vm/nr_hugepages\fR
!  
! .fi
! .if n \{\
  .RE
! .\}
! .RE
! .if n \{\
! .sp
! .\}
! .RS 4
! .it 1 an-trap
! .nr an-no-space-flag 1
! .nr an-break-flag 1
! .br
! .ps +1
! \fBNote\fR
! .ps -1
! .br
! .TS
! allbox tab(:);
! l.
! T{
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Note that the values contained in
! \fB/proc\fR
! will reset after you reboot your system, so may want to set them in an initialization script (for example,
! \fBrc\&.local\fR
! or
! \fBsysctl\&.conf\fR)\&.
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! If you configure (or resize) the OS kernel parameters
! \fB/proc/sys/kernel/shmmax\fR
! or
! \fB/proc/sys/vm/nr_hugepages\fR, Java processes may allocate large pages for areas in addition to the Java heap\&. These steps can allocate large pages for the following areas:
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Java heap
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! Code cache
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! The marking bitmap data structure for the parallel GC
! .RE
! .sp
! Consequently, if you configure the
! \fBnr_hugepages\fR
! parameter to the size of the Java heap, then the JVM can fail in allocating the code cache areas on large pages because these areas are quite large in size\&.
! .RE
! T}
! .TE
! .sp 1
! .sp .5v
! .RE
! .RE
! .SH "EXIT STATUS"
  .PP
! The following exit values are typically returned by the launcher when the launcher is called with the wrong arguments, serious errors, or exceptions thrown by the JVM\&. However, a Java application may choose to return any value by using the API call
! \fBSystem\&.exit(exitValue)\fR\&. The values are:
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! \fB0\fR: Successful completion
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! \fB>0\fR: An error occurred
! .RE
! .SH "SEE ALSO"
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! javac(1)
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! jdb(1)
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! jar(1)
! .RE
! .sp
! .RS 4
! .ie n \{\
! \h'-04'\(bu\h'+03'\c
! .\}
! .el \{\
! .sp -1
! .IP \(bu 2.3
! .\}
! jstat(1)
! .RE
! .br
! 'pl 8.5i
! 'bp
--- 18,5637 ----
  .\"
  .\" Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  .\" or visit www.oracle.com if you need additional information or have any
  .\" questions.
  .\"
! .\" Automatically generated by Pandoc 2.3.1
  .\"
! .TH "JAVA" "1" "2019" "JDK 13" "JDK Commands"
! .hy
! .SH NAME
  .PP
! java \- launch a Java application
! .SH SYNOPSIS
  .PP
! To launch a class file:
  .PP
! \f[CB]java\f[R] [\f[I]options\f[R]] \f[I]mainclass\f[R] [\f[I]args\f[R] ...]
  .PP
! To launch the main class in a JAR file:
  .PP
! \f[CB]java\f[R] [\f[I]options\f[R]] \f[CB]\-jar\f[R] \f[I]jarfile\f[R]
! [\f[I]args\f[R] ...]
  .PP
! To launch the main class in a module:
  .PP
! \f[CB]java\f[R] [\f[I]options\f[R]] \f[CB]\-m\f[R]
! \f[I]module\f[R][\f[CB]/\f[R]\f[I]mainclass\f[R]] [\f[I]args\f[R] ...]
  .PP
  or
  .PP
! \f[CB]java\f[R] [\f[I]options\f[R]] \f[CB]\-\-module\f[R]
! \f[I]module\f[R][\f[CB]/\f[R]\f[I]mainclass\f[R]] [\f[I]args\f[R] ...]
  .PP
! To launch a single source\-file program:
  .PP
! \f[CB]java\f[R] [\f[I]options\f[R]] \f[I]source\-file\f[R] [\f[I]args\f[R]
! \&...]
! .TP
! .B \f[I]options\f[R]
! Optional: Specifies command\-line options separated by spaces.
! See \f[B]Overview of Java Options\f[R] for a description of available
! options.
! .RS
  .RE
! .TP
! .B \f[I]mainclass\f[R]
! Specifies the name of the class to be launched.
! Command\-line entries following \f[CB]classname\f[R] are the arguments for
! the main method.
! .RS
  .RE
! .TP
! .B \f[CB]\-jar\f[R] \f[I]jarfile\f[R]
! Executes a program encapsulated in a JAR file.
! The \f[I]jarfile\f[R] argument is the name of a JAR file with a manifest
! that contains a line in the form \f[CB]Main\-Class:\f[R]\f[I]classname\f[R]
  that defines the class with the
! \f[CB]public\ static\ void\ main(String[]\ args)\f[R] method that serves
! as your application\[aq]s starting point.
! When you use \f[CB]\-jar\f[R], the specified JAR file is the source of all
! user classes, and other class path settings are ignored.
! If you\[aq]re using JAR files, then see \f[B]jar\f[R].
! .RS
! .RE
! .TP
! .B \f[CB]\-m\f[R] or \f[CB]\-\-module\f[R] \f[I]module\f[R][\f[CB]/\f[R]\f[I]mainclass\f[R]]
! Executes the main class in a module specified by \f[I]mainclass\f[R] if
! it is given, or, if it is not given, the value in the \f[I]module\f[R].
! In other words, \f[I]mainclass\f[R] can be used when it is not specified
! by the module, or to override the value when it is specified.
! .RS
! .PP
! See \f[B]Standard Options for Java\f[R].
! .RE
! .TP
! .B \f[I]source\-file\f[R]
! Only used to launch a single source\-file program.
! Specifies the source file that contains the main class when using
! source\-file mode.
! See \f[B]Using Source\-File Mode to Launch Single\-File Source\-Code
! Programs\f[R]
! .RS
! .RE
! .TP
! .B \f[I]args\f[R] ...
! Optional: Arguments following \f[I]mainclass\f[R], \f[I]source\-file\f[R],
! \f[CB]\-jar\f[R] \f[I]jarfile\f[R], and \f[CB]\-m\f[R] or \f[CB]\-\-module\f[R]
! \f[I]module\f[R]\f[CB]/\f[R]\f[I]mainclass\f[R] are passed as arguments to
! the main class.
! .RS
! .RE
! .SH DESCRIPTION
! .PP
! The \f[CB]java\f[R] command starts a Java application.
! It does this by starting the Java Runtime Environment (JRE), loading the
! specified class, and calling that class\[aq]s \f[CB]main()\f[R] method.
! The method must be declared \f[CB]public\f[R] and \f[CB]static\f[R], it must
! not return any value, and it must accept a \f[CB]String\f[R] array as a
! parameter.
! The method declaration has the following form:
! .RS
! .PP
! \f[CB]public\ static\ void\ main(String[]\ args)\f[R]
! .RE
! .PP
! In source\-file mode, the \f[CB]java\f[R] command can launch a class
! declared in a source file.
! See \f[B]Using Source\-File Mode to Launch Single\-File Source\-Code
! Programs\f[R] for a description of using the source\-file mode.
! .RS
! .PP
! \f[B]Note:\f[R] You can use the \f[CB]JDK_JAVA_OPTIONS\f[R] launcher
! environment variable to prepend its content to the actual command line
! of the \f[CB]java\f[R] launcher.
! See \f[B]Using the JDK_JAVA_OPTIONS Launcher Environment Variable\f[R].
! .RE
! .PP
! By default, the first argument that isn\[aq]t an option of the
! \f[CB]java\f[R] command is the fully qualified name of the class to be
! called.
! If \f[CB]\-jar\f[R] is specified, then its argument is the name of the JAR
! file containing class and resource files for the application.
! The startup class must be indicated by the \f[CB]Main\-Class\f[R] manifest
! header in its manifest file.
! .PP
! Arguments after the class file name or the JAR file name are passed to
! the \f[CB]main()\f[R] method.
! .SS \f[CB]javaw\f[R]
! .PP
! \f[B]Windows:\f[R] The \f[CB]javaw\f[R] command is identical to
! \f[CB]java\f[R], except that with \f[CB]javaw\f[R] there\[aq]s no associated
! console window.
! Use \f[CB]javaw\f[R] when you don\[aq]t want a command prompt window to
! appear.
! The \f[CB]javaw\f[R] launcher will, however, display a dialog box with
! error information if a launch fails.
! .SH USING SOURCE\-FILE MODE TO LAUNCH SINGLE\-FILE SOURCE\-CODE PROGRAMS
! .PP
! To launch a class declared in a source file, run the \f[CB]java\f[R]
! launcher in source\-file mode.
! Entering source\-file mode is determined by two items on the
! \f[CB]java\f[R] command line:
! .IP \[bu] 2
! The first item on the command line that is not an option or part of an
! option.
! In other words, the item in the command line that would otherwise be the
! main class name.
! .IP \[bu] 2
! The \f[CB]\-\-source\f[R] \f[I]version\f[R] option, if present.
! .PP
! If the class identifies an existing file that has a \f[CB]\&.java\f[R]
! extension, or if the \f[CB]\-\-source\f[R] option is specified, then
! source\-file mode is selected.
! The source file is then compiled and run.
! The \f[CB]\-\-source\f[R] option can be used to specify the source
! \f[I]version\f[R] or \f[I]N\f[R] of the source code.
! This determines the API that can be used.
! When you set \f[CB]\-\-source\f[R] \f[I]N\f[R], you can only use the public
! API that was defined in JDK \f[I]N\f[R].
! .RS
! .PP
! \f[B]Note:\f[R] The valid values of \f[I]N\f[R] change for each release,
! with new values added and old values removed.
! You\[aq]ll get an error message if you use a value of \f[I]N\f[R] that is
! no longer supported.
! Supported values of \f[I]N\f[R] for this release are \f[CB]7\f[R],
! \f[CB]8\f[R], \f[CB]9\f[R], \f[CB]10\f[R], \f[CB]11\f[R], \f[CB]12\f[R], and
! \f[CB]13\f[R].
! .RE
! .PP
! If the file does not have the \f[CB]\&.java\f[R] extension, the
! \f[CB]\-\-source\f[R] option must be used to tell the \f[CB]java\f[R]
! command to use the source\-file mode.
! The \f[CB]\-\-source\f[R] option is used for cases when the source file is
! a "script" to be executed and the name of the source file does not
! follow the normal naming conventions for Java source files.
! .PP
! In source\-file mode, the effect is as though the source file is
! compiled into memory, and the first class found in the source file is
! executed.
! Any arguments placed after the name of the source file in the original
! command line are passed to the compiled class when it is executed.
! .PP
! For example, if a file were named \f[CB]HelloWorld.java\f[R] and contained
! a class named \f[CB]hello.World\f[R], then the source\-file mode command
! to launch the class would be:
! .RS
! .PP
! \f[CB]java\ HelloWorld.java\f[R]
! .RE
! .PP
! The example illustrates that the class can be in a named package, and
! does not need to be in the unnamed package.
! This use of source\-file mode is informally equivalent to using the
! following two commands where \f[CB]hello.World\f[R] is the name of the
! class in the package:
! .IP
! .nf
! \f[CB]
! javac\ \-d\ <memory>\ HelloWorld.java
! java\ \-cp\ <memory>\ hello.World
! \f[R]
! .fi
! .PP
! \f[B]In source\-file mode, any additional command\-line options are
! processed as follows:\f[R]
! .IP \[bu] 2
! The launcher scans the options specified before the source file for any
! that are relevant in order to compile the source file.
! .RS 2
! .PP
! This includes: \f[CB]\-\-class\-path\f[R], \f[CB]\-\-module\-path\f[R],
! \f[CB]\-\-add\-exports\f[R], \f[CB]\-\-add\-modules\f[R],
! \f[CB]\-\-limit\-modules\f[R], \f[CB]\-\-patch\-module\f[R],
! \f[CB]\-\-upgrade\-module\-path\f[R], and any variant forms of those
! options.
! It also includes the new \f[CB]\-\-enable\-preview\f[R] option, described
! in JEP 12.
! .RE
! .IP \[bu] 2
! No provision is made to pass any additional options to the compiler,
! such as \f[CB]\-processor\f[R] or \f[CB]\-Werror\f[R].
! .IP \[bu] 2
! Command\-line argument files (\f[CB]\@\f[R]\-files) may be used in the
! standard way.
! Long lists of arguments for either the VM or the program being invoked
! may be placed in files specified on the command\-line by prefixing the
! filename with an \f[CB]\@\f[R] character.
! .PP
! \f[B]In source\-file mode, compilation proceeds as follows:\f[R]
! .IP \[bu] 2
! Any command\-line options that are relevant to the compilation
! environment are taken into account.
! .IP \[bu] 2
! No other source files are found and compiled, as if the source path is
! set to an empty value.
! .IP \[bu] 2
! Annotation processing is disabled, as if \f[CB]\-proc:none\f[R] is in
! effect.
! .IP \[bu] 2
! If a version is specified, via the \f[CB]\-\-source\f[R] option, the value
! is used as the argument for an implicit \f[CB]\-\-release\f[R] option for
! the compilation.
! This sets both the source version accepted by compiler and the system
! API that may be used by the code in the source file.
! .IP \[bu] 2
! The source file is compiled in the context of an unnamed module.
! .IP \[bu] 2
! The source file should contain one or more top\-level classes, the first
! of which is taken as the class to be executed.
! .IP \[bu] 2
! The compiler does not enforce the optional restriction defined at the
! end of JLS §7.6, that a type in a named package should exist in a file
! whose name is composed from the type name followed by the
! \f[CB]\&.java\f[R] extension.
! .IP \[bu] 2
! If the source file contains errors, appropriate error messages are
! written to the standard error stream, and the launcher exits with a
! non\-zero exit code.
! .PP
! \f[B]In source\-file mode, execution proceeds as follows:\f[R]
! .IP \[bu] 2
! The class to be executed is the first top\-level class found in the
! source file.
! It must contain a declaration of the standard
! \f[CB]public\ static\ void\ main(String[])\f[R] method.
! .IP \[bu] 2
! The compiled classes are loaded by a custom class loader, that delegates
! to the application class loader.
! This implies that classes appearing on the application class path cannot
! refer to any classes declared in the source file.
! .IP \[bu] 2
! The compiled classes are executed in the context of an unnamed module,
! as though \f[CB]\-\-add\-modules=ALL\-DEFAULT\f[R] is in effect.
! This is in addition to any other \f[CB]\-\-add\-module\f[R] options that
! may be have been specified on the command line.
! .IP \[bu] 2
! Any arguments appearing after the name of the file on the command line
! are passed to the standard main method in the obvious way.
! .IP \[bu] 2
! It is an error if there is a class on the application class path whose
! name is the same as that of the class to be executed.
! .PP
! See \f[B]JEP 330: Launch Single\-File Source\-Code Programs\f[R]
! [http://openjdk.java.net/jeps/330] for complete details.
! .SH USING THE JDK_JAVA_OPTIONS LAUNCHER ENVIRONMENT VARIABLE
! .PP
! \f[CB]JDK_JAVA_OPTIONS\f[R] prepends its content to the options parsed
! from the command line.
! The content of the \f[CB]JDK_JAVA_OPTIONS\f[R] environment variable is a
! list of arguments separated by white\-space characters (as determined by
! \f[CB]isspace()\f[R]).
! These are prepended to the command line arguments passed to
! \f[CB]java\f[R] launcher.
! The encoding requirement for the environment variable is the same as the
! \f[CB]java\f[R] command line on the system.
! \f[CB]JDK_JAVA_OPTIONS\f[R] environment variable content is treated in the
! same manner as that specified in the command line.
! .PP
! Single (\f[CB]\[aq]\f[R]) or double (\f[CB]"\f[R]) quotes can be used to
! enclose arguments that\ contain whitespace characters.
! All content between the open quote and the first matching close quote
! are preserved by simply removing the pair of quotes.
! In case a matching quote is not found, the launcher will abort with an
! error message.
! \f[CB]\@\f[R]\-files are supported as they are specified in the command
! line.
! However, as in \f[CB]\@\f[R]\-files, use of a wildcard is not supported.
! In order to mitigate potential misuse of \f[CB]JDK_JAVA_OPTIONS\f[R]
! behavior, options that specify the main class (such as \f[CB]\-jar\f[R])
! or cause the \f[CB]java\f[R] launcher to exit without executing the main
! class (such as \f[CB]\-h\f[R]) are disallowed in the environment variable.
! If any of these options appear in the environment variable, the launcher
! will abort with an error message.
! When \f[CB]JDK_JAVA_OPTIONS\f[R] is set, the launcher prints a message to
! stderr as a reminder.
! .PP
! \f[B]Example:\f[R]
! .IP
! .nf
! \f[CB]
! $\ export\ JDK_JAVA_OPTIONS=\[aq]\-g\ \@file1\ \-Dprop=value\ \@file2\ \-Dws.prop="white\ spaces"\[aq]
! $\ java\ \-Xint\ \@file3
! \f[R]
! .fi
! .PP
! is equivalent to the command line:
! .IP
! .nf
! \f[CB]
! java\ \-g\ \@file1\ \-Dprop=value\ \@file2\ \-Dws.prop="white\ spaces"\ \-Xint\ \@file3
! \f[R]
! .fi
! .SH OVERVIEW OF JAVA OPTIONS
! .PP
! The \f[CB]java\f[R] command supports a wide range of options in the
! following categories:
! .IP \[bu] 2
! \f[B]Standard Options for Java\f[R]: Options guaranteed to be supported
! by all implementations of the Java Virtual Machine (JVM).
! They\[aq]re used for common actions, such as checking the version of the
! JRE, setting the class path, enabling verbose output, and so on.
! .IP \[bu] 2
! \f[B]Extra Options for Java\f[R]: General purpose options that are
! specific to the Java HotSpot Virtual Machine.
! They aren\[aq]t guaranteed to be supported by all JVM implementations,
! and are subject to change.
! These options start with \f[CB]\-X\f[R].
! .PP
! The advanced options aren\[aq]t recommended for casual use.
! These are developer options used for tuning specific areas of the Java
! HotSpot Virtual Machine operation that often have specific system
! requirements and may require privileged access to system configuration
! parameters.
! Several examples of performance tuning are provided in \f[B]Performance
! Tuning Examples\f[R].
! These options aren\[aq]t guaranteed to be supported by all JVM
! implementations and are subject to change.
! Advanced options start with \f[CB]\-XX\f[R].
! .IP \[bu] 2
! \f[B]Advanced Runtime Options for Java\f[R]: Control the runtime behavior
! of the Java HotSpot VM.
! .IP \[bu] 2
! \f[B]Advanced JIT Compiler Options for java\f[R]: Control the dynamic
! just\-in\-time (JIT) compilation performed by the Java HotSpot VM.
! .IP \[bu] 2
! \f[B]Advanced Serviceability Options for Java\f[R]: Enable gathering
! system information and performing extensive debugging.
! .IP \[bu] 2
! \f[B]Advanced Garbage Collection Options for Java\f[R]: Control how
! garbage collection (GC) is performed by the Java HotSpot
! .PP
! Boolean options are used to either enable a feature that\[aq]s disabled
! by default or disable a feature that\[aq]s enabled by default.
! Such options don\[aq]t require a parameter.
! Boolean \f[CB]\-XX\f[R] options are enabled using the plus sign
! (\f[CB]\-XX:+\f[R]\f[I]OptionName\f[R]) and disabled using the minus sign
! (\f[CB]\-XX:\-\f[R]\f[I]OptionName\f[R]).
! .PP
! For options that require an argument, the argument may be separated from
! the option name by a space, a colon (:), or an equal sign (=), or the
! argument may directly follow the option (the exact syntax differs for
! each option).
! If you\[aq]re expected to specify the size in bytes, then you can use no
! suffix, or use the suffix \f[CB]k\f[R] or \f[CB]K\f[R] for kilobytes (KB),
! \f[CB]m\f[R] or \f[CB]M\f[R] for megabytes (MB), or \f[CB]g\f[R] or \f[CB]G\f[R]
! for gigabytes (GB).
! For example, to set the size to 8 GB, you can specify either
! \f[CB]8g\f[R], \f[CB]8192m\f[R], \f[CB]8388608k\f[R], or \f[CB]8589934592\f[R]
! as the argument.
! If you are expected to specify the percentage, then use a number from 0
! to 1.
! For example, specify \f[CB]0.25\f[R] for 25%.
! .PP
! The following sections describe the options that are obsolete,
! deprecated, and removed:
! .IP \[bu] 2
! \f[B]Deprecated Java Options\f[R]: Accepted and acted upon \-\-\- a
! warning is issued when they\[aq]re used.
! .IP \[bu] 2
! \f[B]Obsolete Java Options\f[R]: Accepted but ignored \-\-\- a warning is
! issued when they\[aq]re used.
! .IP \[bu] 2
! \f[B]Removed Java Options\f[R]: Removed \-\-\- using them results in an
! error.
! .SH STANDARD OPTIONS FOR JAVA
! .PP
! These are the most commonly used options supported by all
! implementations of the JVM.
! .RS
! .PP
! \f[B]Note:\f[R] To specify an argument for a long option, you can use
! either \f[CB]\-\-\f[R]\f[I]name\f[R]\f[CB]=\f[R]\f[I]value\f[R] or
! \f[CB]\-\-\f[R]\f[I]name\f[R] \f[I]value\f[R].
! .RE
! .TP
! .B \f[CB]\-agentlib:\f[R]\f[I]libname\f[R][\f[CB]=\f[R]\f[I]options\f[R]]
! Loads the specified native agent library.
! After the library name, a comma\-separated list of options specific to
! the library can be used.
! .RS
! .IP \[bu] 2
! \f[B]Oracle Solaris, Linux, and macOS:\f[R] If the option
! \f[CB]\-agentlib:foo\f[R] is specified, then the JVM attempts to load the
! library named \f[CB]libfoo.so\f[R] in the location specified by the
! \f[CB]LD_LIBRARY_PATH\f[R] system variable (on macOS this variable is
! \f[CB]DYLD_LIBRARY_PATH\f[R]).
! .IP \[bu] 2
! \f[B]Windows:\f[R] If the option \f[CB]\-agentlib:foo\f[R] is specified,
! then the JVM attempts to load the library named \f[CB]foo.dll\f[R] in the
! location specified by the \f[CB]PATH\f[R] system variable.
! .RS 2
! .PP
! The following example shows how to load the Java Debug Wire Protocol
! (JDWP) library and listen for the socket connection on port 8000,
! suspending the JVM before the main class loads:
! .RS
! .PP
! \f[CB]\-agentlib:jdwp=transport=dt_socket,server=y,address=8000\f[R]
! .RE
! .RE
! .RE
! .TP
! .B \f[CB]\-agentpath:\f[R]\f[I]pathname\f[R][\f[CB]=\f[R]\f[I]options\f[R]]
! Loads the native agent library specified by the absolute path name.
! This option is equivalent to \f[CB]\-agentlib\f[R] but uses the full path
! and file name of the library.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-class\-path\f[R] \f[I]classpath\f[R], \f[CB]\-classpath\f[R] \f[I]classpath\f[R], or \f[CB]\-cp\f[R] \f[I]classpath\f[R]
! A semicolon (\f[CB];\f[R]) separated list of directories, JAR archives,
! and ZIP archives to search for class files.
! .RS
! .PP
! Specifying \f[I]classpath\f[R] overrides any setting of the
! \f[CB]CLASSPATH\f[R] environment variable.
! If the class path option isn\[aq]t used and \f[I]classpath\f[R] isn\[aq]t
! set, then the user class path consists of the current directory (.).
! .PP
! As a special convenience, a class path element that contains a base name
! of an asterisk (*) is considered equivalent to specifying a list of all
! the files in the directory with the extension \f[CB]\&.jar\f[R] or
! \f[CB]\&.JAR\f[R] .
! A Java program can\[aq]t tell the difference between the two
! invocations.
! For example, if the directory mydir contains \f[CB]a.jar\f[R] and
! \f[CB]b.JAR\f[R], then the class path element mydir/* is expanded to
! \f[CB]A.jar:b.JAR\f[R], except that the order of JAR files is unspecified.
! All \f[CB]\&.jar\f[R] files in the specified directory, even hidden ones,
! are included in the list.
! A class path entry consisting of an asterisk (*) expands to a list of
! all the jar files in the current directory.
! The \f[CB]CLASSPATH\f[R] environment variable, where defined, is similarly
! expanded.
! Any class path wildcard expansion that occurs before the Java VM is
! started.
! Java programs never see wildcards that aren\[aq]t expanded except by
! querying the environment, such as by calling
! \f[CB]System.getenv("CLASSPATH")\f[R].
! .RE
! .TP
! .B \f[CB]\-\-disable\-\@files\f[R]
! Can be used anywhere on the command line, including in an argument file,
! to prevent further \f[CB]\@filename\f[R] expansion.
! This option stops expanding \f[CB]\@\f[R]\-argfiles after the option.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-enable\-preview\f[R]
! Allows classes to depend on \f[B]preview features\f[R]
! [https://docs.oracle.com/en/java/javase/12/language/index.html#JSLAN\-GUID\-5A82FE0E\-0CA4\-4F1F\-B075\-564874FE2823]
! of the release.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-module\-path\f[R] \f[I]modulepath\f[R]... or \f[CB]\-p\f[R] \f[I]modulepath\f[R]
! A semicolon (\f[CB];\f[R]) separated list of directories in which each
! directory is a directory of modules.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-upgrade\-module\-path\f[R] \f[I]modulepath\f[R]...
! A semicolon (\f[CB];\f[R]) separated list of directories in which each
! directory is a directory of modules that replace upgradeable modules in
! the runtime image.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-add\-modules\f[R] \f[I]module\f[R][\f[CB],\f[R]\f[I]module\f[R]...]
! Specifies the root modules to resolve in addition to the initial module.
! \f[I]module\f[R] also can be \f[CB]ALL\-DEFAULT\f[R], \f[CB]ALL\-SYSTEM\f[R],
! and \f[CB]ALL\-MODULE\-PATH\f[R].
! .RS
! .RE
! .TP
! .B \f[CB]\-\-list\-modules\f[R]
! Lists the observable modules and then exits.
! .RS
! .RE
! .TP
! .B \f[CB]\-d\f[R] \f[I]module_name\f[R] or \f[CB]\-\-describe\-module\f[R] \f[I]module_name\f[R]
! Describes a specified module and then exits.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-dry\-run\f[R]
! Creates the VM but doesn\[aq]t execute the main method.
! This \f[CB]\-\-dry\-run\f[R] option might be useful for validating the
! command\-line options such as the module system configuration.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-validate\-modules\f[R]
! Validates all modules and exit.
! This option is helpful for finding conflicts and other errors with
! modules on the module path.
! .RS
! .RE
! .TP
! .B \f[CB]\-D\f[R]\f[I]property\f[R]\f[CB]=\f[R]\f[I]value\f[R]
! Sets a system property value.
! The \f[I]property\f[R] variable is a string with no spaces that
! represents the name of the property.
! The \f[I]value\f[R] variable is a string that represents the value of the
! property.
! If \f[I]value\f[R] is a string with spaces, then enclose it in quotation
! marks (for example \f[CB]\-Dfoo="foo\ bar"\f[R]).
! .RS
! .RE
! .TP
! .B \f[CB]\-disableassertions\f[R][\f[CB]:\f[R][\f[I]packagename\f[R]]...|\f[CB]:\f[R]\f[I]classname\f[R]] or \f[CB]\-da\\[\f[R]:\f[CB]\\[*packagename*\\]...|\f[R]:`\f[I]classname\f[R]]
! Disables assertions.
! By default, assertions are disabled in all packages and classes.
! With no arguments, \f[CB]\-disableassertions\f[R] (\f[CB]\-da\f[R]) disables
! assertions in all packages and classes.
! With the \f[I]packagename\f[R] argument ending in \f[CB]\&...\f[R], the
! switch disables assertions in the specified package and any subpackages.
! If the argument is simply \f[CB]\&...\f[R], then the switch disables
! assertions in the unnamed package in the current working directory.
! With the \f[I]classname\f[R] argument, the switch disables assertions in
! the specified class.
! .RS
! .PP
! The \f[CB]\-disableassertions\f[R] (\f[CB]\-da\f[R]) option applies to all
! class loaders and to system classes (which don\[aq]t have a class
! loader).
! There\[aq]s one exception to this rule: If the option is provided with
! no arguments, then it doesn\[aq]t apply to system classes.
! This makes it easy to disable assertions in all classes except for
! system classes.
! The \f[CB]\-disablesystemassertions\f[R] option enables you to disable
! assertions in all system classes.
! To explicitly enable assertions in specific packages or classes, use the
! \f[CB]\-enableassertions\f[R] (\f[CB]\-ea\f[R]) option.
! Both options can be used at the same time.
! For example, to run the \f[CB]MyClass\f[R] application with assertions
! enabled in the package \f[CB]com.wombat.fruitbat\f[R] (and any
! subpackages) but disabled in the class
! \f[CB]com.wombat.fruitbat.Brickbat\f[R], use the following command:
! .RS
! .PP
! \f[CB]java\ \-ea:com.wombat.fruitbat...\ \-da:com.wombat.fruitbat.Brickbat\ MyClass\f[R]
! .RE
! .RE
! .TP
! .B \f[CB]\-disablesystemassertions\f[R] or \f[CB]\-dsa\f[R]
! Disables assertions in all system classes.
! .RS
! .RE
! .TP
! .B \f[CB]\-enableassertions\f[R][\f[CB]:\f[R][\f[I]packagename\f[R]]...|\f[CB]:\f[R]\f[I]classname\f[R]] or \f[CB]\-ea\\[\f[R]:\f[CB]\\[*packagename*\\]...|\f[R]:`\f[I]classname\f[R]]
! Enables assertions.
! By default, assertions are disabled in all packages and classes.
! With no arguments, \f[CB]\-enableassertions\f[R] (\f[CB]\-ea\f[R]) enables
! assertions in all packages and classes.
! With the \f[I]packagename\f[R] argument ending in \f[CB]\&...\f[R], the
! switch enables assertions in the specified package and any subpackages.
! If the argument is simply \f[CB]\&...\f[R], then the switch enables
! assertions in the unnamed package in the current working directory.
! With the \f[I]classname\f[R] argument, the switch enables assertions in
! the specified class.
! .RS
! .PP
! The \f[CB]\-enableassertions\f[R] (\f[CB]\-ea\f[R]) option applies to all
! class loaders and to system classes (which don\[aq]t have a class
! loader).
! There\[aq]s one exception to this rule: If the option is provided with
! no arguments, then it doesn\[aq]t apply to system classes.
! This makes it easy to enable assertions in all classes except for system
! classes.
! The \f[CB]\-enablesystemassertions\f[R] option provides a separate switch
! to enable assertions in all system classes.
! To explicitly disable assertions in specific packages or classes, use
! the \f[CB]\-disableassertions\f[R] (\f[CB]\-da\f[R]) option.
! If a single command contains multiple instances of these switches, then
! they\[aq]re processed in order, before loading any classes.
! For example, to run the \f[CB]MyClass\f[R] application with assertions
! enabled only in the package \f[CB]com.wombat.fruitbat\f[R] (and any
! subpackages) but disabled in the class
! \f[CB]com.wombat.fruitbat.Brickbat\f[R], use the following command:
! .RS
! .PP
! \f[CB]java\ \-ea:com.wombat.fruitbat...\ \-da:com.wombat.fruitbat.Brickbat\ MyClass\f[R]
! .RE
! .RE
! .TP
! .B \f[CB]\-enablesystemassertions\f[R] or \f[CB]\-esa\f[R]
! Enables assertions in all system classes.
! .RS
! .RE
! .TP
! .B \f[CB]\-help\f[R], \f[CB]\-h\f[R], or \f[CB]\-?\f[R]
! Prints the help message to the error stream.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-help\f[R]
! Prints the help message to the output stream.
! .RS
! .RE
! .TP
! .B \f[CB]\-javaagent:\f[R]\f[I]jarpath\f[R][\f[CB]=\f[R]\f[I]options\f[R]]
! Loads the specified Java programming language agent.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-show\-version\f[R]
! Prints the product version to the output stream and continues.
! .RS
! .RE
! .TP
! .B \f[CB]\-showversion\f[R]
! Prints the product version to the error stream and continues.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-show\-module\-resolution\f[R]
! Shows module resolution output during startup.
! .RS
! .RE
! .TP
! .B \f[CB]\-splash:\f[R]\f[I]imagepath\f[R]
! Shows the splash screen with the image specified by \f[I]imagepath\f[R].
! HiDPI scaled images are automatically supported and used if available.
! The unscaled image file name, such as \f[CB]image.ext\f[R], should always
! be passed as the argument to the \f[CB]\-splash\f[R] option.
! The most appropriate scaled image provided is picked up automatically.
! .RS
! .PP
! For example, to show the \f[CB]splash.gif\f[R] file from the
! \f[CB]images\f[R] directory when starting your application, use the
! following option:
! .RS
! .PP
! \f[CB]\-splash:images/splash.gif\f[R]
! .RE
! .PP
! See the SplashScreen API documentation for more information.
! .RE
! .TP
! .B \f[CB]\-verbose:class\f[R]
! Displays information about each loaded class.
! .RS
! .RE
! .TP
! .B \f[CB]\-verbose:gc\f[R]
! Displays information about each garbage collection (GC) event.
! .RS
! .RE
! .TP
! .B \f[CB]\-verbose:jni\f[R]
! Displays information about the use of native methods and other Java
! Native Interface (JNI) activity.
! .RS
! .RE
! .TP
! .B \f[CB]\-verbose:module\f[R]
! Displays information about the modules in use.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-version\f[R]
! Prints product version to the error stream and exits.
! .RS
! .RE
! .TP
! .B \f[CB]\-version\f[R]
! Prints product version to the output stream and exits.
! .RS
! .RE
! .TP
! .B \f[CB]\-X\f[R]
! Prints the help on extra options to the error stream.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-help\-extra\f[R]
! Prints the help on extra options to the output stream.
! .RS
! .RE
! .TP
! .B \f[CB]\@\f[R]\f[I]argfile\f[R]
! Specifies one or more argument files prefixed by \f[CB]\@\f[R] used by the
! \f[CB]java\f[R] command.
! It isn\[aq]t uncommon for the \f[CB]java\f[R] command line to be very long
! because of the \f[CB]\&.jar\f[R] files needed in the classpath.
! The \f[CB]\@\f[R]\f[I]argfile\f[R] option overcomes command\-line length
! limitations by enabling the launcher to expand the contents of argument
! files after shell expansion, but before argument processing.
! Contents in the argument files are expanded because otherwise, they
! would be specified on the command line until the
! \f[CB]\-Xdisable\-\@files\f[R] option was encountered.
! .RS
! .PP
! The argument files can also contain the main class name and all options.
! If an argument file contains all of the options required by the
! \f[CB]java\f[R] command, then the command line could simply be:
! .RS
! .PP
! \f[CB]java\ \@\f[R]\f[I]argfile\f[R]
! .RE
! .PP
! See \f[B]java Command\-Line Argument Files\f[R] for a description and
! examples of using \f[CB]\@\f[R]\-argfiles.
! .RE
! .SH EXTRA OPTIONS FOR JAVA
! .PP
! The following \f[CB]java\f[R] options are general purpose options that are
! specific to the Java HotSpot Virtual Machine.
! .TP
! .B \f[CB]\-Xbatch\f[R]
! Disables background compilation.
! By default, the JVM compiles the method as a background task, running
! the method in interpreter mode until the background compilation is
! finished.
! The \f[CB]\-Xbatch\f[R] flag disables background compilation so that
! compilation of all methods proceeds as a foreground task until
! completed.
! This option is equivalent to \f[CB]\-XX:\-BackgroundCompilation\f[R].
! .RS
! .RE
! .TP
! .B \f[CB]\-Xbootclasspath/a:\f[R]\f[I]directories\f[R]|\f[I]zip\f[R]|\f[I]JAR\-files\f[R]
! Specifies a list of directories, JAR files, and ZIP archives to append
! to the end of the default bootstrap class path.
! .RS
! .PP
! \f[B]Oracle Solaris, Linux, and macOS:\f[R] Colons (\f[CB]:\f[R]) separate
! entities in this list.
! .PP
! \f[B]Windows:\f[R] Semicolons (\f[CB];\f[R]) separate entities in this
! list.
! .RE
! .TP
! .B \f[CB]\-Xcheck:jni\f[R]
! Performs additional checks for Java Native Interface (JNI) functions.
! Specifically, it validates the parameters passed to the JNI function and
! the runtime environment data before processing the JNI request.
! It also checks for pending exceptions between JNI calls.
! Any invalid data encountered indicates a problem in the native code, and
! the JVM terminates with an irrecoverable error in such cases.
! Expect a performance degradation when this option is used.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xcomp\f[R]
! Forces compilation of methods on first invocation.
! By default, the Client VM (\f[CB]\-client\f[R]) performs 1,000 interpreted
! method invocations and the Server VM (\f[CB]\-server\f[R]) performs 10,000
! interpreted method invocations to gather information for efficient
! compilation.
! Specifying the \f[CB]\-Xcomp\f[R] option disables interpreted method
! invocations to increase compilation performance at the expense of
! efficiency.
! You can also change the number of interpreted method invocations before
! compilation using the \f[CB]\-XX:CompileThreshold\f[R] option.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xdebug\f[R]
! Does nothing.
! Provided for backward compatibility.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xdiag\f[R]
! Shows additional diagnostic messages.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xint\f[R]
! Runs the application in interpreted\-only mode.
! Compilation to native code is disabled, and all bytecode is executed by
! the interpreter.
! The performance benefits offered by the just\-in\-time (JIT) compiler
! aren\[aq]t present in this mode.
! .RS
  .RE
! .TP
! .B \f[CB]\-Xinternalversion\f[R]
  Displays more detailed JVM version information than the
! \f[CB]\-version\f[R] option, and then exits.
! .RS
  .RE
! .TP
! .B \f[CB]\-Xlog:\f[R]\f[I]option\f[R]
! Configure or enable logging with the Java Virtual Machine (JVM) unified
! logging framework.
! See \f[B]Enable Logging with the JVM Unified Logging Framework\f[R].
! .RS
! .RE
! .TP
! .B \f[CB]\-Xmixed\f[R]
! Executes all bytecode by the interpreter except for hot methods, which
! are compiled to native code.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xmn\f[R] \f[I]size\f[R]
! Sets the initial and maximum size (in bytes) of the heap for the young
! generation (nursery).
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
! \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
! \f[CB]G\f[R] to indicate gigabytes.
! The young generation region of the heap is used for new objects.
! GC is performed in this region more often than in other regions.
! If the size for the young generation is too small, then a lot of minor
! garbage collections are performed.
! If the size is too large, then only full garbage collections are
! performed, which can take a long time to complete.
! It is recommended that you keep the size for the young generation
! greater than 25% and less than 50% of the overall heap size.
! The following examples show how to set the initial and maximum size of
! young generation to 256 MB using various units:
! .RS
! .IP
! .nf
! \f[CB]
! \-Xmn256m
! \-Xmn262144k
! \-Xmn268435456
! \f[R]
! .fi
! .PP
! Instead of the \f[CB]\-Xmn\f[R] option to set both the initial and maximum
! size of the heap for the young generation, you can use
! \f[CB]\-XX:NewSize\f[R] to set the initial size and
! \f[CB]\-XX:MaxNewSize\f[R] to set the maximum size.
! .RE
! .TP
! .B \f[CB]\-Xms\f[R] \f[I]size\f[R]
! Sets the initial size (in bytes) of the heap.
! This value must be a multiple of 1024 and greater than 1 MB.
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
! \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, \f[CB]g\f[R] or \f[CB]G\f[R]
! to indicate gigabytes.
! The following examples show how to set the size of allocated memory to 6
! MB using various units:
! .RS
! .IP
! .nf
! \f[CB]
! \-Xms6291456
! \-Xms6144k
! \-Xms6m
! \f[R]
! .fi
! .PP
! If you don\[aq]t set this option, then the initial size is set as the
! sum of the sizes allocated for the old generation and the young
! generation.
! The initial size of the heap for the young generation can be set using
! the \f[CB]\-Xmn\f[R] option or the \f[CB]\-XX:NewSize\f[R] option.
! .RE
! .TP
! .B \f[CB]\-Xmx\f[R] \f[I]size\f[R]
! Specifies the maximum size (in bytes) of the memory allocation pool in
! bytes.
! This value must be a multiple of 1024 and greater than 2 MB.
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
! \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
! \f[CB]G\f[R] to indicate gigabytes.
! The default value is chosen at runtime based on system configuration.
! For server deployments, \f[CB]\-Xms\f[R] and \f[CB]\-Xmx\f[R] are often set
! to the same value.
! The following examples show how to set the maximum allowed size of
! allocated memory to 80 MB using various units:
! .RS
! .IP
! .nf
! \f[CB]
! \-Xmx83886080
! \-Xmx81920k
! \-Xmx80m
! \f[R]
! .fi
! .PP
! The \f[CB]\-Xmx\f[R] option is equivalent to \f[CB]\-XX:MaxHeapSize\f[R].
! .RE
! .TP
! .B \f[CB]\-Xnoclassgc\f[R]
! Disables garbage collection (GC) of classes.
! This can save some GC time, which shortens interruptions during the
! application run.
! When you specify \f[CB]\-Xnoclassgc\f[R] at startup, the class objects in
! the application are left untouched during GC and are always be
! considered live.
! This can result in more memory being permanently occupied which, if not
! used carefully, throws an out\-of\-memory exception.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xrs\f[R]
! Reduces the use of operating system signals by the JVM.
! Shutdown hooks enable the orderly shutdown of a Java application by
! running user cleanup code (such as closing database connections) at
! shutdown, even if the JVM terminates abruptly.
! .RS
! .IP \[bu] 2
! \f[B]Oracle Solaris, Linux, and macOS:\f[R]
! .RS 2
! .IP \[bu] 2
! The JVM catches signals to implement shutdown hooks for unexpected
! termination.
! The JVM uses \f[CB]SIGHUP\f[R], \f[CB]SIGINT\f[R], and \f[CB]SIGTERM\f[R] to
! initiate the running of shutdown hooks.
! .IP \[bu] 2
  Applications embedding the JVM frequently need to trap signals such as
! \f[CB]SIGINT\f[R] or \f[CB]SIGTERM\f[R], which can lead to interference with
! the JVM signal handlers.
! The \f[CB]\-Xrs\f[R] option is available to address this issue.
! When \f[CB]\-Xrs\f[R] is used, the signal masks for \f[CB]SIGINT\f[R],
! \f[CB]SIGTERM\f[R], \f[CB]SIGHUP\f[R], and \f[CB]SIGQUIT\f[R] aren\[aq]t
! changed by the JVM, and signal handlers for these signals aren\[aq]t
! installed.
! .RE
! .IP \[bu] 2
! \f[B]Windows:\f[R]
! .RS 2
! .IP \[bu] 2
! The JVM watches for console control events to implement shutdown hooks
! for unexpected termination.
! Specifically, the JVM registers a console control handler that begins
! shutdown\-hook processing and returns \f[CB]TRUE\f[R] for
! \f[CB]CTRL_C_EVENT\f[R], \f[CB]CTRL_CLOSE_EVENT\f[R],
! \f[CB]CTRL_LOGOFF_EVENT\f[R], and \f[CB]CTRL_SHUTDOWN_EVENT\f[R].
! .IP \[bu] 2
! The JVM uses a similar mechanism to implement the feature of dumping
! thread stacks for debugging purposes.
! The JVM uses \f[CB]CTRL_BREAK_EVENT\f[R] to perform thread dumps.
! .IP \[bu] 2
! If the JVM is run as a service (for example, as a servlet engine for a
! web server), then it can receive \f[CB]CTRL_LOGOFF_EVENT\f[R] but
! shouldn\[aq]t initiate shutdown because the operating system doesn\[aq]t
! actually terminate the process.
! To avoid possible interference such as this, the \f[CB]\-Xrs\f[R] option
! can be used.
! When the \f[CB]\-Xrs\f[R] option is used, the JVM doesn\[aq]t install a
! console control handler, implying that it doesn\[aq]t watch for or
! process \f[CB]CTRL_C_EVENT\f[R], \f[CB]CTRL_CLOSE_EVENT\f[R],
! \f[CB]CTRL_LOGOFF_EVENT\f[R], or \f[CB]CTRL_SHUTDOWN_EVENT\f[R].
! .RE
! .PP
! There are two consequences of specifying \f[CB]\-Xrs\f[R]:
! .IP \[bu] 2
! \f[B]Oracle Solaris, Linux, and macOS:\f[R] \f[CB]SIGQUIT\f[R] thread dumps
! aren\[aq]t available.
! .IP \[bu] 2
! \f[B]Windows:\f[R] Ctrl + Break thread dumps aren\[aq]t available.
! .PP
! User code is responsible for causing shutdown hooks to run, for example,
! by calling the \f[CB]System.exit()\f[R] when the JVM is to be terminated.
! .RE
! .TP
! .B \f[CB]\-Xshare:\f[R]\f[I]mode\f[R]
! Sets the class data sharing (CDS) mode.
! .RS
! .PP
! Possible \f[I]mode\f[R] arguments for this option include the following:
! .TP
! .B \f[CB]auto\f[R]
! Use shared class data if possible (default).
! .RS
! .RE
! .TP
! .B \f[CB]on\f[R]
! Require using shared class data, otherwise fail.
! .RS
! .RE
! .RS
! .PP
! \f[B]Note:\f[R] The \f[CB]\-Xshare:on\f[R] option is used for testing
! purposes only and may cause intermittent failures due to the use of
! address space layout randomization by the operation system.
! This option should not be used in production environments.
! .RE
! .TP
! .B \f[CB]off\f[R]
! Do not attempt to use shared class data.
! .RS
! .RE
! .RE
! .TP
! .B \f[CB]\-XshowSettings\f[R]
! Shows all settings and then continues.
! .RS
! .RE
! .TP
! .B \f[CB]\-XshowSettings:\f[R]\f[I]category\f[R]
! Shows settings and continues.
! Possible \f[I]category\f[R] arguments for this option include the
! following:
! .RS
! .TP
! .B \f[CB]all\f[R]
! Shows all categories of settings.
! This is the default value.
! .RS
! .RE
! .TP
! .B \f[CB]locale\f[R]
! Shows settings related to locale.
! .RS
! .RE
! .TP
! .B \f[CB]properties\f[R]
! Shows settings related to system properties.
! .RS
! .RE
! .TP
! .B \f[CB]vm\f[R]
! Shows the settings of the JVM.
! .RS
! .RE
! .TP
! .B \f[CB]system\f[R]
! \f[B]Linux:\f[R] Shows host system or container configuration and
! continues.
! .RS
! .RE
! .RE
! .TP
! .B \f[CB]\-Xss\f[R] \f[I]size\f[R]
! Sets the thread stack size (in bytes).
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate KB, \f[CB]m\f[R] or
! \f[CB]M\f[R] to indicate MB, or \f[CB]g\f[R] or \f[CB]G\f[R] to indicate GB.
! The default value depends on the platform:
! .RS
! .IP \[bu] 2
  Linux/x64 (64\-bit): 1024 KB
! .IP \[bu] 2
! macOS (64\-bit): 1024 KB
! .IP \[bu] 2
! Oracle Solaris (64\-bit): 1024 KB
! .IP \[bu] 2
! Windows: The default value depends on virtual memory
! .PP
! The following examples set the thread stack size to 1024 KB in different
! units:
! .IP
! .nf
! \f[CB]
! \-Xss1m
! \-Xss1024k
! \-Xss1048576
! \f[R]
! .fi
! .PP
! This option is similar to \f[CB]\-XX:ThreadStackSize\f[R].
! .RE
! .TP
! .B \f[CB]\-\-add\-reads\f[R] \f[I]module\f[R]\f[CB]=\f[R]\f[I]target\-module\f[R](\f[CB],\f[R]\f[I]target\-module\f[R])*
! Updates \f[I]module\f[R] to read the \f[I]target\-module\f[R], regardless
! of the module declaration.
! \f[I]target\-module\f[R] can be all unnamed to read all unnamed modules.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-add\-exports\f[R] \f[I]module\f[R]\f[CB]/\f[R]\f[I]package\f[R]\f[CB]=\f[R]\f[I]target\-module\f[R](\f[CB],\f[R]\f[I]target\-module\f[R])*
! Updates \f[I]module\f[R] to export \f[I]package\f[R] to
! \f[I]target\-module\f[R], regardless of module declaration.
! The \f[I]target\-module\f[R] can be all unnamed to export to all unnamed
! modules.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-add\-opens\f[R] \f[I]module\f[R]\f[CB]/\f[R]\f[I]package\f[R]\f[CB]=\f[R]\f[I]target\-module\f[R](\f[CB],\f[R]\f[I]target\-module\f[R])*
! Updates \f[I]module\f[R] to open \f[I]package\f[R] to
! \f[I]target\-module\f[R], regardless of module declaration.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-illegal\-access=\f[R]\f[I]parameter\f[R]
! When present at run time, \f[CB]\-\-illegal\-access=\f[R] takes a keyword
! \f[I]parameter\f[R] to specify a mode of operation:
! .RS
! .RS
! .PP
! \f[B]Note:\f[R] This option will be removed in a future release.
! .RE
! .IP \[bu] 2
! \f[CB]permit\f[R]: This mode opens each package in each module in the
! run\-time image to code in all unnamed modules ( such as code on the
! class path), if that package existed in JDK 8.
! This enables both static access, (for example, by compiled bytecode, and
! deep reflective access) through the platform\[aq]s various reflection
! APIs.
! The first reflective\-access operation to any such package causes a
! warning to be issued.
! However, no warnings are issued after the first occurrence.
! This single warning describes how to enable further warnings.
! This mode is the default for the current JDK but will change in a future
! release.
! .IP \[bu] 2
! \f[CB]warn\f[R]: This mode is identical to \f[CB]permit\f[R] except that a
! warning message is issued for each illegal reflective\-access operation.
! .IP \[bu] 2
! \f[CB]debug\f[R]: This mode is identical to \f[CB]warn\f[R] except that both
! a warning message and a stack trace are issued for each illegal
! reflective\-access operation.
! .IP \[bu] 2
! \f[CB]deny\f[R]: This mode disables all illegal\-access operations except
! for those enabled by other command\-line options, such as
! \f[CB]\-\-add\-opens\f[R].
! This mode will become the default in a future release.
! .PP
! The default mode, \f[CB]\-\-illegal\-access=permit\f[R], is intended to
! make you aware of code on the class path that reflectively accesses any
! JDK\-internal APIs at least once.
! To learn about all such accesses, you can use the \f[CB]warn\f[R] or the
! \f[CB]debug\f[R] modes.
! For each library or framework on the class path that requires illegal
! access, you have two options:
! .IP \[bu] 2
! If the component\[aq]s maintainers have already released a fixed version
! that no longer uses JDK\-internal APIs then you can consider upgrading
! to that version.
! .IP \[bu] 2
! If the component still needs to be fixed, then you can contact its
! maintainers and ask them to replace their use of JDK\-internal APIs with
! the proper exported APIs.
! .PP
! If you must continue to use a component that requires illegal access,
! then you can eliminate the warning messages by using one or more
! \f[CB]\-\-add\-opens\f[R] options to open only those internal packages to
! which access is required.
! .PP
! To verify that your application is ready for a future version of the
! JDK, run it with \f[CB]\-\-illegal\-access=deny\f[R] along with any
! necessary \f[CB]\-\-add\-opens\f[R] options.
! Any remaining illegal\-access errors will most likely be due to static
! references from compiled code to JDK\-internal APIs.
! You can identify those by running the \f[B]jdeps\f[R] tool with the
! \f[CB]\-\-jdk\-internals\f[R] option.
! For performance reasons, the current JDK does not issue warnings for
! illegal static\-access operations.
! .RE
! .TP
! .B \f[CB]\-\-limit\-modules\f[R] \f[I]module\f[R][\f[CB],\f[R]\f[I]module\f[R]...]
! Specifies the limit of the universe of observable modules.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-patch\-module\f[R] \f[I]module\f[R]\f[CB]=\f[R]\f[I]file\f[R](\f[CB];\f[R]\f[I]file\f[R])*
! Overrides or augments a module with classes and resources in JAR files
! or directories.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-disable\-\@files\f[R]
! Can be used anywhere on the command line, including in an argument file,
! to prevent further \f[CB]\@\f[R]\f[I]filename\f[R] expansion.
! This option stops expanding \f[CB]\@\f[R]\-argfiles after the option.
! .RS
! .RE
! .TP
! .B \f[CB]\-\-source\f[R] \f[I]version\f[R]
! Sets the version of the source in source\-file mode.
! .RS
! .RE
! .SH EXTRA OPTIONS FOR MACOS
! .PP
! The following extra options are macOS specific.
! .TP
! .B \f[CB]\-XstartOnFirstThread\f[R]
! Runs the \f[CB]main()\f[R] method on the first (AppKit) thread.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xdock:name=\f[R]\f[I]application_name\f[R]
! Overrides the default application name displayed in dock.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xdock:icon=\f[R]\f[I]path_to_icon_file\f[R]
! Overrides the default icon displayed in dock.
! .RS
! .RE
! .SH ADVANCED OPTIONS FOR JAVA
! .PP
! These \f[CB]java\f[R] options can be used to enable other advanced
! options.
! .TP
! .B \f[CB]\-XX:+UnlockDiagnosticVMOptions\f[R]
! Unlocks the options intended for diagnosing the JVM.
! By default, this option is disabled and diagnostic options aren\[aq]t
! available.
! .RS
! .PP
! Command line options that are enabled with the use of this option are
! not supported.
! If you encounter issues while using any of these options, it is very
! likely that you will be required to reproduce the problem without using
! any of these unsupported options before Oracle Support can assist with
! an investigation.
! It is also possible that any of these options may be removed or their
! behavior changed without any warning.
! .RE
! .TP
! .B \f[CB]\-XX:+UnlockExperimentalVMOptions\f[R]
! Unlocks the options that provide experimental features in the JVM.
! By default, this option is disabled and experimental features aren\[aq]t
! available.
! .RS
! .RE
! .SH ADVANCED RUNTIME OPTIONS FOR JAVA
! .PP
! These \f[CB]java\f[R] options control the runtime behavior of the Java
! HotSpot VM.
! .TP
! .B \f[CB]\-XX:ActiveProcessorCount=\f[R]\f[I]x\f[R]
! Overrides the number of CPUs that the VM will use to calculate the size
! of thread pools it will use for various operations such as Garbage
! Collection and ForkJoinPool.
! .RS
! .PP
! The VM normally determines the number of available processors from the
! operating system.
! This flag can be useful for partitioning CPU resources when running
! multiple Java processes in docker containers.
! This flag is honored even if \f[CB]UseContainerSupport\f[R] is not
! enabled.
! See \f[CB]\-XX:\-UseContainerSupport\f[R] for a description of enabling
! and disabling container support.
! .RE
! .TP
! .B \f[CB]\-XX:AllocateHeapAt=\f[R]\f[I]path\f[R]
! Takes a path to the file system and uses memory mapping to allocate the
! object heap on the memory device.
! Using this option enables the HotSpot VM to allocate the Java object
! heap on an alternative memory device, such as an NV\-DIMM, specified by
! the user.
! .RS
! .PP
! Alternative memory devices that have the same semantics as DRAM,
! including the semantics of atomic operations, can be used instead of
! DRAM for the object heap without changing the existing application code.
! All other memory structures (such as the code heap, metaspace, and
! thread stacks) continue to reside in DRAM.
! .PP
! Some operating systems expose non\-DRAM memory through the file system.
! Memory\-mapped files in these file systems bypass the page cache and
! provide a direct mapping of virtual memory to the physical memory on the
! device.
! The existing heap related flags (such as \f[CB]\-Xmx\f[R] and
! \f[CB]\-Xms\f[R]) and garbage\-collection related flags continue to work
! as before.
! .RE
! .TP
! .B \f[CB]\-XX:\-CompactStrings\f[R]
! Disables the Compact Strings feature.
! By default, this option is enabled.
! When this option is enabled, Java Strings containing only single\-byte
! characters are internally represented and stored as
! single\-byte\-per\-character Strings using ISO\-8859\-1 / Latin\-1
! encoding.
! This reduces, by 50%, the amount of space required for Strings
! containing only single\-byte characters.
! For Java Strings containing at least one multibyte character: these are
! represented and stored as 2 bytes per character using UTF\-16 encoding.
! Disabling the Compact Strings feature forces the use of UTF\-16 encoding
! as the internal representation for all Java Strings.
! .RS
! .PP
! Cases where it may be beneficial to disable Compact Strings include the
! following:
! .IP \[bu] 2
! When it\[aq]s known that an application overwhelmingly will be
! allocating multibyte character Strings
! .IP \[bu] 2
! In the unexpected event where a performance regression is observed in
! migrating from Java SE 8 to Java SE 9 and an analysis shows that Compact
! Strings introduces the regression
! .PP
! In both of these scenarios, disabling Compact Strings makes sense.
! .RE
! .TP
! .B \f[CB]\-XX:ErrorFile=\f[R]\f[I]filename\f[R]
! Specifies the path and file name to which error data is written when an
! irrecoverable error occurs.
! By default, this file is created in the current working directory and
! named \f[CB]hs_err_pid\f[R]\f[I]pid\f[R]\f[CB]\&.log\f[R] where \f[I]pid\f[R]
! is the identifier of the process that encountered the error.
! .RS
! .PP
! The following example shows how to set the default log file (note that
! the identifier of the process is specified as \f[CB]%p\f[R]):
! .RS
! .PP
! \f[CB]\-XX:ErrorFile=./hs_err_pid%p.log\f[R]
! .RE
! .IP \[bu] 2
! \f[B]Oracle Solaris, Linux, and macOS:\f[R] The following example shows
! how to set the error log to \f[CB]/var/log/java/java_error.log\f[R]:
! .RS 2
! .RS
! .PP
! \f[CB]\-XX:ErrorFile=/var/log/java/java_error.log\f[R]
! .RE
! .RE
! .IP \[bu] 2
! \f[B]Windows:\f[R] The following example shows how to set the error log
! file to \f[CB]C:/log/java/java_error.log\f[R]:
! .RS 2
! .RS
! .PP
! \f[CB]\-XX:ErrorFile=C:/log/java/java_error.log\f[R]
! .RE
! .RE
! .PP
! If the file exists, and is writeable, then it will be overwritten.
! Otherwise, if the file can\[aq]t be created in the specified directory
! (due to insufficient space, permission problem, or another issue), then
! the file is created in the temporary directory for the operating system:
! .IP \[bu] 2
! \f[B]Oracle Solaris, Linux, and macOS:\f[R] The temporary directory is
! \f[CB]/tmp\f[R].
! .IP \[bu] 2
! \f[B]Windows:\f[R] The temporary directory is specified by the value of
! the \f[CB]TMP\f[R] environment variable; if that environment variable
! isn\[aq]t defined, then the value of the \f[CB]TEMP\f[R] environment
! variable is used.
! .RE
! .TP
! .B \f[CB]\-XX:+ExtensiveErrorReports\f[R]
! Enables the reporting of more extensive error information in the
! \f[CB]ErrorFile\f[R].
! This option can be turned on in environments where maximal information
! is desired \- even if the resulting logs may be quite large and/or
! contain information that might be considered sensitive.
! The information can vary from release to release, and across different
! platforms.
! By default this option is disabled.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:+FlightRecorder\f[R]
! Enables the use of Java Flight Recorder (JFR) during the runtime of the
! application.
! .RS
! .RS
! .PP
! \f[B]Note:\f[R] The \f[CB]\-XX:+FlightRecorder\f[R] option is no longer
! required to use JFR.
! This was a change made in JDK 8u40.
! .RE
! .RE
! .TP
! .B \f[CB]\-XX:FlightRecorderOptions=\f[R]\f[I]parameter\f[R]\f[CB]=\f[R]\f[I]value\f[R]
! Sets the parameters that control the behavior of JFR.
! .RS
! .PP
! The following list contains the available JFR
! \f[I]parameter\f[R]\f[CB]=\f[R]\f[I]value\f[R] entries:
! .TP
! .B \f[CB]allow_threadbuffers_to_disk=\f[R]{\f[CB]true\f[R]|\f[CB]false\f[R]}
! Specifies whether thread buffers are written directly to disk if the
! buffer thread is blocked.
! By default, this parameter is disabled.
! .RS
! .RE
! .TP
! .B \f[CB]globalbuffersize=\f[R]\f[I]size\f[R]
! Specifies the total amount of primary memory used for data retention.
! The default value is based on the value specified for
! \f[CB]memorysize\f[R].
! Change the \f[CB]memorysize\f[R] parameter to alter the size of global
! buffers.
! .RS
! .RE
! .TP
! .B \f[CB]maxchunksize=\f[R]\f[I]size\f[R]
! Specifies the maximum size (in bytes) of the data chunks in a recording.
! Append \f[CB]m\f[R] or \f[CB]M\f[R] to specify the size in megabytes (MB),
! or \f[CB]g\f[R] or \f[CB]G\f[R] to specify the size in gigabytes (GB).
! By default, the maximum size of data chunks is set to 12 MB.
! The minimum allowed is 1 MB.
! .RS
! .RE
! .TP
! .B \f[CB]memorysize=\f[R]\f[I]size\f[R]
! Determines how much buffer memory should be used, and sets the
! \f[CB]globalbuffersize\f[R] and \f[CB]numglobalbuffers\f[R] parameters based
! on the size specified.
! Append \f[CB]m\f[R] or \f[CB]M\f[R] to specify the size in megabytes (MB),
! or \f[CB]g\f[R] or \f[CB]G\f[R] to specify the size in gigabytes (GB).
! By default, the memory size is set to 10 MB.
! .RS
! .RE
! .TP
! .B \f[CB]numglobalbuffers\f[R]
! Specifies the number of global buffers used.
! The default value is based on the memory size specified.
! Change the \f[CB]memorysize\f[R] parameter to alter the number of global
! buffers.
! .RS
! .RE
! .TP
! .B \f[CB]old\-object\-queue\-size=number\-of\-objects\f[R]
! Maximum number of old objects to track.
! By default, the number of objects is set to 256.
! .RS
! .RE
! .TP
! .B \f[CB]repository=\f[R]\f[I]path\f[R]
! Specifies the repository (a directory) for temporary disk storage.
! By default, the system\[aq]s temporary directory is used.
! .RS
! .RE
! .TP
! .B \f[CB]retransform=\f[R]{\f[CB]true\f[R]|\f[CB]false\f[R]}
! Specifies whether event classes should be retransformed using JVMTI.
! If false, instrumentation is added when event classes are loaded.
! By default, this parameter is enabled.
! .RS
! .RE
! .TP
! .B \f[CB]samplethreads=\f[R]{\f[CB]true\f[R]|\f[CB]false\f[R]}
! Specifies whether thread sampling is enabled.
! Thread sampling occurs only if the sampling event is enabled along with
! this parameter.
! By default, this parameter is enabled.
! .RS
! .RE
! .TP
! .B \f[CB]stackdepth=\f[R]\f[I]depth\f[R]
! Stack depth for stack traces.
! By default, the depth is set to 64 method calls.
! The maximum is 2048.
! Values greater than 64 could create significant overhead and reduce
! performance.
! .RS
! .RE
! .TP
! .B \f[CB]threadbuffersize=\f[R]\f[I]size\f[R]
! Specifies the per\-thread local buffer size (in bytes).
! By default, the local buffer size is set to 8 kilobytes.
! Overriding this parameter could reduce performance and is not
! recommended.
! .RS
! .RE
! .PP
! You can specify values for multiple parameters by separating them with a
! comma.
! .RE
! .TP
! .B \f[CB]\-XX:LargePageSizeInBytes=\f[R]\f[I]size\f[R]
! Sets the maximum size (in bytes) for large pages used for the Java heap.
! The \f[I]size\f[R] argument must be a power of 2 (2, 4, 8, 16, and so
! on).
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
! \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
! \f[CB]G\f[R] to indicate gigabytes.
! By default, the size is set to 0, meaning that the JVM chooses the size
! for large pages automatically.
! See \f[B]Large Pages\f[R].
! .RS
! .PP
! The following example describes how to set the large page size to 4
! megabytes (MB):
! .RS
! .PP
! \f[CB]\-XX:LargePageSizeInBytes=4m\f[R]
! .RE
! .RE
! .TP
! .B \f[CB]\-XX:MaxDirectMemorySize=\f[R]\f[I]size\f[R]
! Sets the maximum total size (in bytes) of the \f[CB]java.nio\f[R] package,
! direct\-buffer allocations.
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
! \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
! \f[CB]G\f[R] to indicate gigabytes.
! By default, the size is set to 0, meaning that the JVM chooses the size
! for NIO direct\-buffer allocations automatically.
! .RS
! .PP
! The following examples illustrate how to set the NIO size to 1024 KB in
! different units:
! .IP
! .nf
! \f[CB]
! \-XX:MaxDirectMemorySize=1m
! \-XX:MaxDirectMemorySize=1024k
! \-XX:MaxDirectMemorySize=1048576
! \f[R]
! .fi
! .RE
! .TP
! .B \f[CB]\-XX:\-MaxFDLimit\f[R]
! Disables the attempt to set the soft limit for the number of open file
! descriptors to the hard limit.
! By default, this option is enabled on all platforms, but is ignored on
! Windows.
! The only time that you may need to disable this is on Mac OS, where its
! use imposes a maximum of 10240, which is lower than the actual system
! maximum.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:NativeMemoryTracking=\f[R]\f[I]mode\f[R]
! Specifies the mode for tracking JVM native memory usage.
! Possible \f[I]mode\f[R] arguments for this option include the following:
! .RS
! .TP
! .B \f[CB]off\f[R]
! Instructs not to track JVM native memory usage.
! This is the default behavior if you don\[aq]t specify the
! \f[CB]\-XX:NativeMemoryTracking\f[R] option.
! .RS
! .RE
! .TP
! .B \f[CB]summary\f[R]
! Tracks memory usage only by JVM subsystems, such as Java heap, class,
! code, and thread.
! .RS
! .RE
! .TP
! .B \f[CB]detail\f[R]
! In addition to tracking memory usage by JVM subsystems, track memory
! usage by individual \f[CB]CallSite\f[R], individual virtual memory region
! and its committed regions.
! .RS
! .RE
! .RE
! .TP
! .B \f[CB]\-XX:ObjectAlignmentInBytes=\f[R]\f[I]alignment\f[R]
! Sets the memory alignment of Java objects (in bytes).
! By default, the value is set to 8 bytes.
! The specified value should be a power of 2, and must be within the range
! of 8 and 256 (inclusive).
! This option makes it possible to use compressed pointers with large Java
! heap sizes.
! .RS
  .PP
  The heap size limit in bytes is calculated as:
! .RS
  .PP
! \f[CB]4GB\ *\ ObjectAlignmentInBytes\f[R]
  .RE
+ .RS
  .PP
! \f[B]Note:\f[R] As the alignment value increases, the unused space
! between objects also increases.
! As a result, you may not realize any benefits from using compressed
! pointers with large Java heap sizes.
! .RE
! .RE
! .TP
! .B \f[CB]\-XX:OnError=\f[R]\f[I]string\f[R]
! Sets a custom command or a series of semicolon\-separated commands to
! run when an irrecoverable error occurs.
! If the string contains spaces, then it must be enclosed in quotation
! marks.
! .RS
! .IP \[bu] 2
! \f[B]Oracle Solaris, Linux, and macOS:\f[R] The following example shows
! how the \f[CB]\-XX:OnError\f[R] option can be used to run the
! \f[CB]gcore\f[R] command to create a core image, and start the
! \f[CB]gdb\f[R] debugger to attach to the process in case of an
! irrecoverable error (the \f[CB]%p\f[R] designates the current process
! identifier):
! .RS 2
! .RS
! .PP
! \f[CB]\-XX:OnError="gcore\ %p;gdb\ \-p\ %p"\f[R]
! .RE
! .RE
! .IP \[bu] 2
! \f[B]Windows:\f[R] The following example shows how the
! \f[CB]\-XX:OnError\f[R] option can be used to run the
! \f[CB]userdump.exe\f[R] utility to obtain a crash dump in case of an
! irrecoverable error (the \f[CB]%p\f[R] designates the current process
! identifier).
! This example assumes that the path to the \f[CB]userdump.exe\f[R] utility
! is specified in the \f[CB]PATH\f[R] environment variable:
! .RS 2
! .RS
! .PP
! \f[CB]\-XX:OnError="userdump.exe\ %p"\f[R]
! .RE
! .RE
! .RE
! .TP
! .B \f[CB]\-XX:OnOutOfMemoryError=\f[R]\f[I]string\f[R]
! Sets a custom command or a series of semicolon\-separated commands to
! run when an \f[CB]OutOfMemoryError\f[R] exception is first thrown.
! If the string contains spaces, then it must be enclosed in quotation
! marks.
! For an example of a command string, see the description of the
! \f[CB]\-XX:OnError\f[R] option.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:+PrintCommandLineFlags\f[R]
! Enables printing of ergonomically selected JVM flags that appeared on
! the command line.
! It can be useful to know the ergonomic values set by the JVM, such as
! the heap space size and the selected garbage collector.
! By default, this option is disabled and flags aren\[aq]t printed.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:+PreserveFramePointer\f[R]
! Selects between using the RBP register as a general purpose register
! (\f[CB]\-XX:\-PreserveFramePointer\f[R]) and using the RBP register to
! hold the frame pointer of the currently executing method
! (\f[CB]\-XX:+PreserveFramePointer\f[R] .
! If the frame pointer is available, then external profiling tools\ (for
! example, Linux perf) can construct more accurate stack traces.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:+PrintNMTStatistics\f[R]
! Enables printing of collected native memory tracking data at JVM exit
! when native memory tracking is enabled (see
! \f[CB]\-XX:NativeMemoryTracking\f[R]).
! By default, this option is disabled and native memory tracking data
! isn\[aq]t printed.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:SharedArchiveFile=\f[R]\f[I]path\f[R]
! Specifies the path and name of the class data sharing (CDS) archive file
! .RS
! .PP
! See \f[B]Application Class Data Sharing\f[R].
! .RE
! .TP
! .B \f[CB]\-XX:SharedArchiveConfigFile\f[R]=\f[I]shared_config_file\f[R]
! Specifies additional shared data added to the archive file.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:SharedClassListFile=\f[R]\f[I]file_name\f[R]
! Specifies the text file that contains the names of the classes to store
! in the class data sharing (CDS) archive.
! This file contains the full name of one class per line, except slashes
! (\f[CB]/\f[R]) replace dots (\f[CB]\&.\f[R]).
! For example, to specify the classes \f[CB]java.lang.Object\f[R] and
! \f[CB]hello.Main\f[R], create a text file that contains the following two
! lines:
! .RS
! .IP
! .nf
! \f[CB]
! java/lang/Object
! hello/Main
! \f[R]
! .fi
! .PP
! The classes that you specify in this text file should include the
! classes that are commonly used by the application.
! They may include any classes from the application, extension, or
! bootstrap class paths.
! .PP
! See \f[B]Application Class Data Sharing\f[R].
! .RE
! .TP
! .B \f[CB]\-XX:+ShowMessageBoxOnError\f[R]
! Enables the display of a dialog box when the JVM experiences an
! irrecoverable error.
! This prevents the JVM from exiting and keeps the process active so that
! you can attach a debugger to it to investigate the cause of the error.
! By default, this option is disabled.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:StartFlightRecording=\f[R]\f[I]parameter\f[R]\f[CB]=\f[R]\f[I]value\f[R]
! Starts a JFR recording for the Java application.
! This option is equivalent to the \f[CB]JFR.start\f[R] diagnostic command
! that starts a recording during runtime.
! You can set the following \f[I]parameter\f[R]\f[CB]=\f[R]\f[I]value\f[R]
! entries when starting a JFR recording:
! .RS
! .TP
! .B \f[CB]delay=\f[R]\f[I]time\f[R]
! Specifies the delay between the Java application launch time and the
! start of the recording.
! Append \f[CB]s\f[R] to specify the time in seconds, \f[CB]m\f[R] for
! minutes, \f[CB]h\f[R] for hours, or \f[CB]d\f[R] for days (for example,
! specifying \f[CB]10m\f[R] means 10 minutes).
! By default, there\[aq]s no delay, and this parameter is set to 0.
! .RS
! .RE
! .TP
! .B \f[CB]disk=\f[R]{\f[CB]true\f[R]|\f[CB]false\f[R]}
! Specifies whether to write data to disk while recording.
! By default, this parameter is enabled.
! .RS
! .RE
! .TP
! .B \f[CB]dumponexit=\f[R]{\f[CB]true\f[R]|\f[CB]false\f[R]}
! Specifies if the running recording is dumped when the JVM shuts down.
! If enabled and a \f[CB]filename\f[R] is not entered, the recording is
! written to a file in the directory where the process was started.
! The file name is a system\-generated name that contains the process ID,
! recording ID, and current timestamp, similar to
! \f[CB]hotspot\-pid\-47496\-id\-1\-2018_01_25_19_10_41.jfr\f[R].
! By default, this parameter is disabled.
! .RS
! .RE
! .TP
! .B \f[CB]duration=\f[R]\f[I]time\f[R]
! Specifies the duration of the recording.
! Append \f[CB]s\f[R] to specify the time in seconds, \f[CB]m\f[R] for
! minutes, \f[CB]h\f[R] for hours, or \f[CB]d\f[R] for days (for example,
! specifying \f[CB]5h\f[R] means 5 hours).
! By default, the duration isn\[aq]t limited, and this parameter is set to
! 0.
! .RS
! .RE
! .TP
! .B \f[CB]filename=\f[R]\f[I]path\f[R]
! Specifies the path and name of the file to which the recording is
! written when the recording is stopped, for example:
! .RS
! .IP \[bu] 2
! \f[CB]recording.jfr\f[R]
! .IP \[bu] 2
! \f[CB]/home/user/recordings/recording.jfr\f[R]
! .IP \[bu] 2
! \f[CB]c:\\recordings\\recording.jfr\f[R]
! .RE
! .TP
! .B \f[CB]name=\f[R]\f[I]identifier\f[R]
! Takes both the name and the identifier of a recording.
! .RS
! .RE
! .TP
! .B \f[CB]maxage=\f[R]\f[I]time\f[R]
! Specifies the maximum age of disk data to keep for the recording.
! This parameter is valid only when the \f[CB]disk\f[R] parameter is set to
! \f[CB]true\f[R].
! Append \f[CB]s\f[R] to specify the time in seconds, \f[CB]m\f[R] for
! minutes, \f[CB]h\f[R] for hours, or \f[CB]d\f[R] for days (for example,
! specifying \f[CB]30s\f[R] means 30 seconds).
! By default, the maximum age isn\[aq]t limited, and this parameter is set
! to \f[CB]0s\f[R].
! .RS
! .RE
! .TP
! .B \f[CB]maxsize=\f[R]\f[I]size\f[R]
! Specifies the maximum size (in bytes) of disk data to keep for the
! recording.
! This parameter is valid only when the \f[CB]disk\f[R] parameter is set to
! \f[CB]true\f[R].
! The value must not be less than the value for the \f[CB]maxchunksize\f[R]
! parameter set with \f[CB]\-XX:FlightRecorderOptions\f[R].
! Append \f[CB]m\f[R] or \f[CB]M\f[R] to specify the size in megabytes, or
! \f[CB]g\f[R] or \f[CB]G\f[R] to specify the size in gigabytes.
! By default, the maximum size of disk data isn\[aq]t limited, and this
! parameter is set to \f[CB]0\f[R].
! .RS
! .RE
! .TP
! .B \f[CB]path\-to\-gc\-roots=\f[R]{\f[CB]true\f[R]|\f[CB]false\f[R]}
! Specifies whether to collect the path to garbage collection (GC) roots
! at the end of a recording.
! By default, this parameter is disabled.
! .RS
! .PP
! The path to GC roots is useful for finding memory leaks, but collecting
! it is time\-consuming.
! Enable this option only when you start a recording for an application
! that you suspect has a memory leak.
! If the \f[CB]settings\f[R] parameter is set to \f[CB]profile\f[R], the stack
! trace from where the potential leaking object was allocated is included
! in the information collected.
! .RE
! .TP
! .B \f[CB]settings=\f[R]\f[I]path\f[R]
! Specifies the path and name of the event settings file (of type JFC).
! By default, the \f[CB]default.jfc\f[R] file is used, which is located in
! \f[CB]JRE_HOME/lib/jfr\f[R].
! This default settings file collects a predefined set of information with
! low overhead, so it has minimal impact on performance and can be used
! with recordings that run continuously.
! .RS
! .PP
! A second settings file is also provided, profile.jfc, which provides
! more data than the default configuration, but can have more overhead and
! impact performance.
! Use this configuration for short periods of time when more information
! is needed.
! .RE
! .PP
! You can specify values for multiple parameters by separating them with a
! comma.
! .RE
! .TP
! .B \f[CB]\-XX:ThreadStackSize=\f[R]\f[I]size\f[R]
! Sets the Java thread stack size (in kilobytes).
! Use of a scaling suffix, such as \f[CB]k\f[R], results in the scaling of
! the kilobytes value so that \f[CB]\-XX:ThreadStackSize=1k\f[R] sets the
! Java thread stack size\ to 1024*1024 bytes or 1 megabyte.
! The default value depends on the platform:
! .RS
! .IP \[bu] 2
  Linux/x64 (64\-bit): 1024 KB
! .IP \[bu] 2
! macOS (64\-bit): 1024 KB
! .IP \[bu] 2
! Oracle Solaris (64\-bit): 1024 KB
! .IP \[bu] 2
! Windows: The default value depends on virtual memory
! .PP
! The following examples show how to set the thread stack size to 1
! megabyte in different units:
! .IP
! .nf
! \f[CB]
! \-XX:ThreadStackSize=1k
! \-XX:ThreadStackSize=1024
! \f[R]
! .fi
! .PP
! This option is similar to \f[CB]\-Xss\f[R].
! .RE
! .TP
! .B \f[CB]\-XX:\-UseBiasedLocking\f[R]
! Disables the use of biased locking.
! Some applications with significant amounts of uncontended
! synchronization may attain significant speedups with this flag enabled,
! but applications with certain patterns of locking may see slowdowns.
! \&.
! .RS
! .PP
! By default, this option is enabled.
! .RE
! .TP
! .B \f[CB]\-XX:\-UseCompressedOops\f[R]
! Disables the use of compressed pointers.
! By default, this option is enabled, and compressed pointers are used
! when Java heap sizes are less than 32 GB.
! When this option is enabled, object references are represented as
! 32\-bit offsets instead of 64\-bit pointers, which typically increases
! performance when running the application with Java heap sizes of less
! than 32 GB.
! This option works only for 64\-bit JVMs.
! .RS
! .PP
! It\[aq]s also possible to use compressed pointers when Java heap sizes
! are greater than 32 GB.
! See the \f[CB]\-XX:ObjectAlignmentInBytes\f[R] option.
! .RE
! .TP
! .B \f[CB]\-XX:\-UseContainerSupport\f[R]
! The VM now provides automatic container detection support, which allows
! the VM to determine the amount of memory and number of processors that
! are available to a Java process running in docker containers.
! It uses this information to allocate system resources.
! This support is only available on Linux x64 platforms.
! \ If supported, the default for this flag is\ \f[CB]true\f[R], and
! container support is enabled by default.
! \ It\ can be disabled with\ \f[CB]\-XX:\-UseContainerSupport\f[R].
! .RS
! .PP
! Unified Logging is available to help to diagnose issues related to this
! support.
! .PP
! Use \f[CB]\-Xlog:os+container=trace\f[R] for maximum logging of container
! information.
! See \f[B]Enable Logging with the JVM Unified Logging Framework\f[R] for a
! description of using Unified Logging.
! .RE
! .TP
! .B \f[CB]\-XX:+UseHugeTLBFS\f[R]
! \f[B]Linux only:\f[R] This option is the equivalent of specifying
! \f[CB]\-XX:+UseLargePages\f[R].
! This option is disabled by default.
! This option pre\-allocates all large pages up\-front, when memory is
! reserved; consequently the JVM can\[aq]t dynamically grow or shrink
! large pages memory areas; see \f[CB]\-XX:UseTransparentHugePages\f[R] if
! you want this behavior.
! .RS
! .PP
! See \f[B]Large Pages\f[R].
! .RE
! .TP
! .B \f[CB]\-XX:+UseLargePages\f[R]
! Enables the use of large page memory.
! By default, this option is disabled and large page memory isn\[aq]t
! used.
! .RS
! .PP
! See \f[B]Large Pages\f[R].
! .RE
! .TP
! .B \f[CB]\-XX:+UseTransparentHugePages\f[R]
! \f[B]Linux only:\f[R] Enables the use of large pages that can dynamically
! grow or shrink.
! This option is disabled by default.
! You may encounter performance problems with transparent huge pages as
! the OS moves other pages around to create huge pages; this option is
! made available for experimentation.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:+AllowUserSignalHandlers\f[R]
! Enables installation of signal handlers by the application.
! By default, this option is disabled and the application isn\[aq]t
! allowed to install signal handlers.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:VMOptionsFile=\f[R]\f[I]filename\f[R]
! Allows user to specify VM options in a file, for example,
! \f[CB]java\ \-XX:VMOptionsFile=/var/my_vm_options\ HelloWorld\f[R].
! .RS
! .RE
! .SH ADVANCED JIT COMPILER OPTIONS FOR JAVA
! .PP
! These \f[CB]java\f[R] options control the dynamic just\-in\-time (JIT)
! compilation performed by the Java HotSpot VM.
! .TP
! .B \f[CB]\-XX:AllocateInstancePrefetchLines=\f[R]\f[I]lines\f[R]
! Sets the number of lines to prefetch ahead of the instance allocation
! pointer.
! By default, the number of lines to prefetch is set to 1:
! .RS
! .RS
! .PP
! \f[CB]\-XX:AllocateInstancePrefetchLines=1\f[R]
! .RE
! .PP
! Only the Java HotSpot Server VM supports this option.
! .RE
! .TP
! .B \f[CB]\-XX:AllocatePrefetchDistance=\f[R]\f[I]size\f[R]
! Sets the size (in bytes) of the prefetch distance for object allocation.
! Memory about to be written with the value of new objects is prefetched
! up to this distance starting from the address of the last allocated
! object.
! Each Java thread has its own allocation point.
! .RS
! .PP
! Negative values denote that prefetch distance is chosen based on the
! platform.
! Positive values are bytes to prefetch.
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
! \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
! \f[CB]G\f[R] to indicate gigabytes.
! The default value is set to \-1.
! .PP
! The following example shows how to set the prefetch distance to 1024
! bytes:
! .RS
! .PP
! \f[CB]\-XX:AllocatePrefetchDistance=1024\f[R]
! .RE
! .PP
! Only the Java HotSpot Server VM supports this option.
! .RE
! .TP
! .B \f[CB]\-XX:AllocatePrefetchInstr=\f[R]\f[I]instruction\f[R]
! Sets the prefetch instruction to prefetch ahead of the allocation
! pointer.
! Only the Java HotSpot Server VM supports this option.
! Possible values are from 0 to 3.
! The actual instructions behind the values depend on the platform.
! By default, the prefetch instruction is set to 0:
! .RS
! .RS
! .PP
! \f[CB]\-XX:AllocatePrefetchInstr=0\f[R]
! .RE
! .PP
! Only the Java HotSpot Server VM supports this option.
! .RE
! .TP
! .B \f[CB]\-XX:AllocatePrefetchLines=\f[R]\f[I]lines\f[R]
! Sets the number of cache lines to load after the last object allocation
! by using the prefetch instructions generated in compiled code.
! The default value is 1 if the last allocated object was an instance, and
! 3 if it was an array.
! .RS
! .PP
! The following example shows how to set the number of loaded cache lines
! to 5:
! .RS
! .PP
! \f[CB]\-XX:AllocatePrefetchLines=5\f[R]
! .RE
! .PP
! Only the Java HotSpot Server VM supports this option.
! .RE
! .TP
! .B \f[CB]\-XX:AllocatePrefetchStepSize=\f[R]\f[I]size\f[R]
! Sets the step size (in bytes) for sequential prefetch instructions.
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
! \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, \f[CB]g\f[R] or \f[CB]G\f[R]
! to indicate gigabytes.
! By default, the step size is set to 16 bytes:
! .RS
! .RS
! .PP
! \f[CB]\-XX:AllocatePrefetchStepSize=16\f[R]
! .RE
! .PP
! Only the Java HotSpot Server VM supports this option.
! .RE
! .TP
! .B \f[CB]\-XX:AllocatePrefetchStyle=\f[R]\f[I]style\f[R]
! Sets the generated code style for prefetch instructions.
! The \f[I]style\f[R] argument is an integer from 0 to 3:
! .RS
! .TP
! .B \f[CB]0\f[R]
! Don\[aq]t generate prefetch instructions.
! .RS
! .RE
! .TP
! .B \f[CB]1\f[R]
! Execute prefetch instructions after each allocation.
! This is the default parameter.
! .RS
! .RE
! .TP
! .B \f[CB]2\f[R]
! Use the thread\-local allocation block (TLAB) watermark pointer to
! determine when prefetch instructions are executed.
! .RS
! .RE
! .TP
! .B \f[CB]3\f[R]
! Use BIS instruction on SPARC for allocation prefetch.
! .RS
! .RE
! .PP
! Only the Java HotSpot Server VM supports this option.
! .RE
! .TP
! .B \f[CB]\-XX:+BackgroundCompilation\f[R]
! Enables background compilation.
! This option is enabled by default.
! To disable background compilation, specify
! \f[CB]\-XX:\-BackgroundCompilation\f[R] (this is equivalent to specifying
! \f[CB]\-Xbatch\f[R]).
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:CICompilerCount=\f[R]\f[I]threads\f[R]
! Sets the number of compiler threads to use for compilation.
! By default, the number of threads is set to 2 for the server JVM, to 1
! for the client JVM, and it scales to the number of cores if tiered
! compilation is used.
! The following example shows how to set the number of threads to 2:
! .RS
! .RS
! .PP
! \f[CB]\-XX:CICompilerCount=2\f[R]
! .RE
! .RE
! .TP
! .B \f[CB]\-XX:CompileCommand=\f[R]\f[I]command\f[R]\f[CB],\f[R]\f[I]method\f[R][\f[CB],\f[R]\f[I]option\f[R]]
! Specifies a \f[I]command\f[R] to perform on a \f[I]method\f[R].
! For example, to exclude the \f[CB]indexOf()\f[R] method of the
! \f[CB]String\f[R] class from being compiled, use the following:
! .RS
! .RS
! .PP
! \f[CB]\-XX:CompileCommand=exclude,java/lang/String.indexOf\f[R]
! .RE
! .PP
! Note that the full class name is specified, including all packages and
! subpackages separated by a slash (\f[CB]/\f[R]).
! For easier cut\-and\-paste operations, it\[aq]s also possible to use the
! method name format produced by the \f[CB]\-XX:+PrintCompilation\f[R] and
! \f[CB]\-XX:+LogCompilation\f[R] options:
! .RS
! .PP
! \f[CB]\-XX:CompileCommand=exclude,java.lang.String::indexOf\f[R]
! .RE
! .PP
! If the method is specified without the signature, then the command is
! applied to all methods with the specified name.
! However, you can also specify the signature of the method in the class
! file format.
! In this case, you should enclose the arguments in quotation marks,
! because otherwise the shell treats the semicolon as a command end.
! For example, if you want to exclude only the \f[CB]indexOf(String)\f[R]
! method of the \f[CB]String\f[R] class from being compiled, use the
! following:
! .RS
! .PP
! \f[CB]\-XX:CompileCommand="exclude,java/lang/String.indexOf,(Ljava/lang/String;)I"\f[R]
! .RE
! .PP
! You can also use the asterisk (*) as a wildcard for class and method
! names.
! For example, to exclude all \f[CB]indexOf()\f[R] methods in all classes
! from being compiled, use the following:
! .RS
! .PP
! \f[CB]\-XX:CompileCommand=exclude,*.indexOf\f[R]
! .RE
! .PP
! The commas and periods are aliases for spaces, making it easier to pass
! compiler commands through a shell.
! You can pass arguments to \f[CB]\-XX:CompileCommand\f[R] using spaces as
! separators by enclosing the argument in quotation marks:
! .RS
! .PP
! \f[CB]\-XX:CompileCommand="exclude\ java/lang/String\ indexOf"\f[R]
! .RE
! .PP
! Note that after parsing the commands passed on the command line using
! the \f[CB]\-XX:CompileCommand\f[R] options, the JIT compiler then reads
! commands from the \f[CB]\&.hotspot_compiler\f[R] file.
! You can add commands to this file or specify a different file using the
! \f[CB]\-XX:CompileCommandFile\f[R] option.
! .PP
! To add several commands, either specify the \f[CB]\-XX:CompileCommand\f[R]
! option multiple times, or separate each argument with the new line
! separator (\f[CB]\\n\f[R]).
! The following commands are available:
! .TP
! .B \f[CB]break\f[R]
! Sets a breakpoint when debugging the JVM to stop at the beginning of
! compilation of the specified method.
! .RS
! .RE
! .TP
! .B \f[CB]compileonly\f[R]
! Excludes all methods from compilation except for the specified method.
! As an alternative, you can use the \f[CB]\-XX:CompileOnly\f[R] option,
! which lets you specify several methods.
! .RS
! .RE
! .TP
! .B \f[CB]dontinline\f[R]
! Prevents inlining of the specified method.
! .RS
! .RE
! .TP
! .B \f[CB]exclude\f[R]
! Excludes the specified method from compilation.
! .RS
! .RE
! .TP
! .B \f[CB]help\f[R]
! Prints a help message for the \f[CB]\-XX:CompileCommand\f[R] option.
! .RS
! .RE
! .TP
! .B \f[CB]inline\f[R]
! Attempts to inline the specified method.
! .RS
! .RE
! .TP
! .B \f[CB]log\f[R]
! Excludes compilation logging (with the \f[CB]\-XX:+LogCompilation\f[R]
! option) for all methods except for the specified method.
! By default, logging is performed for all compiled methods.
! .RS
! .RE
! .TP
! .B \f[CB]option\f[R]
! Passes a JIT compilation option to the specified method in place of the
! last argument (\f[CB]option\f[R]).
! The compilation option is set at the end, after the method name.
! For example, to enable the \f[CB]BlockLayoutByFrequency\f[R] option for
! the \f[CB]append()\f[R] method of the \f[CB]StringBuffer\f[R] class, use the
! following:
! .RS
! .RS
! .PP
! \f[CB]\-XX:CompileCommand=option,java/lang/StringBuffer.append,BlockLayoutByFrequency\f[R]
! .RE
! .PP
! You can specify multiple compilation options, separated by commas or
! spaces.
! .RE
! .TP
! .B \f[CB]print\f[R]
! Prints generated assembler code after compilation of the specified
! method.
! .RS
! .RE
! .TP
! .B \f[CB]quiet\f[R]
! Instructs not to print the compile commands.
! By default, the commands that you specify with the
! \f[CB]\-XX:CompileCommand\f[R] option are printed; for example, if you
! exclude from compilation the \f[CB]indexOf()\f[R] method of the
! \f[CB]String\f[R] class, then the following is printed to standard output:
! .RS
! .RS
  .PP
! \f[CB]CompilerOracle:\ exclude\ java/lang/String.indexOf\f[R]
  .RE
  .PP
  You can suppress this by specifying the
! \f[CB]\-XX:CompileCommand=quiet\f[R] option before other
! \f[CB]\-XX:CompileCommand\f[R] options.
  .RE
  .RE
! .TP
! .B \f[CB]\-XX:CompileCommandFile=\f[R]\f[I]filename\f[R]
! Sets the file from which JIT compiler commands are read.
! By default, the \f[CB]\&.hotspot_compiler\f[R] file is used to store
! commands performed by the JIT compiler.
! .RS
! .PP
! Each line in the command file represents a command, a class name, and a
! method name for which the command is used.
! For example, this line prints assembly code for the \f[CB]toString()\f[R]
! method of the \f[CB]String\f[R] class:
! .RS
! .PP
! \f[CB]print\ java/lang/String\ toString\f[R]
! .RE
! .PP
! If you\[aq]re using commands for the JIT compiler to perform on methods,
! then see the \f[CB]\-XX:CompileCommand\f[R] option.
! .RE
! .TP
! .B \f[CB]\-XX:CompilerDirectivesFile=\f[R]\f[I]file\f[R]
! Adds directives from a file to the directives stack when a program
! starts.
! See \f[B]Compiler Control\f[R]
! [https://docs.oracle.com/en/java/javase/12/vm/compiler\-control1.html#GUID\-94AD8194\-786A\-4F19\-BFFF\-278F8E237F3A].
! .RS
! .PP
! The \f[CB]\-XX:CompilerDirectivesFile\f[R] option has to be used together
! with the \f[CB]\-XX:UnlockDiagnosticVMOptions\f[R] option that unlocks
! diagnostic JVM options.
! .RE
! .TP
! .B \f[CB]\-XX:+CompilerDirectivesPrint\f[R]
! Prints the directives stack when the program starts or when a new
! directive is added.
! .RS
! .PP
! The \f[CB]\-XX:+CompilerDirectivesPrint\f[R] option has to be used
! together with the \f[CB]\-XX:UnlockDiagnosticVMOptions\f[R] option that
! unlocks diagnostic JVM options.
! .RE
! .TP
! .B \f[CB]\-XX:CompileOnly=\f[R]\f[I]methods\f[R]
! Sets the list of methods (separated by commas) to which compilation
! should be restricted.
! Only the specified methods are compiled.
! Specify each method with the full class name (including the packages and
! subpackages).
! For example, to compile only the \f[CB]length()\f[R] method of the
! \f[CB]String\f[R] class and the \f[CB]size()\f[R] method of the
! \f[CB]List\f[R] class, use the following:
! .RS
! .RS
! .PP
! \f[CB]\-XX:CompileOnly=java/lang/String.length,java/util/List.size\f[R]
! .RE
! .PP
! Note that the full class name is specified, including all packages and
! subpackages separated by a slash (\f[CB]/\f[R]).
! For easier cut and paste operations, it\[aq]s also possible to use the
! method name format produced by the \f[CB]\-XX:+PrintCompilation\f[R] and
! \f[CB]\-XX:+LogCompilation\f[R] options:
! .RS
! .PP
! \f[CB]\-XX:CompileOnly=java.lang.String::length,java.util.List::size\f[R]
! .RE
! .PP
! Although wildcards aren\[aq]t supported, you can specify only the class
! or package name to compile all methods in that class or package, as well
! as specify just the method to compile methods with this name in any
  class:
! .IP
  .nf
! \f[CB]
! \-XX:CompileOnly=java/lang/String
! \-XX:CompileOnly=java/lang
! \-XX:CompileOnly=.length
! \f[R]
! .fi
! .RE
! .TP
! .B \f[CB]\-XX:CompileThreshold=\f[R]\f[I]invocations\f[R]
! Sets the number of interpreted method invocations before compilation.
! By default, in the server JVM, the JIT compiler performs 10,000
! interpreted method invocations to gather information for efficient
! compilation.
! For the client JVM, the default setting is 1,500 invocations.
! This option is ignored when tiered compilation is enabled; see the
! option \f[CB]\-XX:\-TieredCompilation\f[R].
! The following example shows how to set the number of interpreted method
! invocations to 5,000:
! .RS
! .RS
! .PP
! \f[CB]\-XX:CompileThreshold=5000\f[R]
! .RE
! .PP
! You can completely disable interpretation of Java methods before
! compilation by specifying the \f[CB]\-Xcomp\f[R] option.
! .RE
! .TP
! .B \f[CB]\-XX:CompileThresholdScaling=\f[R]\f[I]scale\f[R]
! Provides unified control of first compilation.
! This option controls when methods are first compiled for both the tiered
! and the nontiered modes of operation.
! The \f[CB]CompileThresholdScaling\f[R] option has an integer value between
! 0 and +Inf and scales the thresholds corresponding to the current mode
! of operation (both tiered and nontiered).
! Setting \f[CB]CompileThresholdScaling\f[R] to a value less than 1.0
! results in earlier compilation while values greater than 1.0 delay
! compilation.
! Setting \f[CB]CompileThresholdScaling\f[R] to 0 is equivalent to disabling
! compilation.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:+DoEscapeAnalysis\f[R]
! Enables the use of escape analysis.
! This option is enabled by default.
! To disable the use of escape analysis, specify
! \f[CB]\-XX:\-DoEscapeAnalysis\f[R].
! Only the Java HotSpot Server VM supports this option.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:InitialCodeCacheSize=\f[R]\f[I]size\f[R]
! Sets the initial code cache size (in bytes).
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
! \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
! \f[CB]G\f[R] to indicate gigabytes.
! The default value is set to 500 KB.
! The initial code cache size shouldn\[aq]t be less than the system\[aq]s
! minimal memory page size.
! The following example shows how to set the initial code cache size to 32
! KB:
! .RS
! .RS
! .PP
! \f[CB]\-XX:InitialCodeCacheSize=32k\f[R]
! .RE
! .RE
! .TP
! .B \f[CB]\-XX:+Inline\f[R]
! Enables method inlining.
! This option is enabled by default to increase performance.
! To disable method inlining, specify \f[CB]\-XX:\-Inline\f[R].
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:InlineSmallCode=\f[R]\f[I]size\f[R]
! Sets the maximum code size (in bytes) for compiled methods that should
! be inlined.
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
! \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
! \f[CB]G\f[R] to indicate gigabytes.
! Only compiled methods with the size smaller than the specified size is
! inlined.
! By default, the maximum code size is set to 1000 bytes:
! .RS
! .RS
  .PP
! \f[CB]\-XX:InlineSmallCode=1000\f[R]
  .RE
  .RE
! .TP
! .B \f[CB]\-XX:+LogCompilation\f[R]
  Enables logging of compilation activity to a file named
! \f[CB]hotspot.log\f[R] in the current working directory.
! You can specify a different log file path and name using the
! \f[CB]\-XX:LogFile\f[R] option.
! .RS
! .PP
! By default, this option is disabled and compilation activity isn\[aq]t
! logged.
! The \f[CB]\-XX:+LogCompilation\f[R] option has to be used together with
! the \f[CB]\-XX:UnlockDiagnosticVMOptions\f[R] option that unlocks
! diagnostic JVM options.
! .PP
! You can enable verbose diagnostic output with a message printed to the
! console every time a method is compiled by using the
! \f[CB]\-XX:+PrintCompilation\f[R] option.
! .RE
! .TP
! .B \f[CB]\-XX:MaxInlineSize=\f[R]\f[I]size\f[R]
! Sets the maximum bytecode size (in bytes) of a method to be inlined.
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
! \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
! \f[CB]G\f[R] to indicate gigabytes.
! By default, the maximum bytecode size is set to 35 bytes:
! .RS
! .RS
! .PP
! \f[CB]\-XX:MaxInlineSize=35\f[R]
! .RE
! .RE
! .TP
! .B \f[CB]\-XX:MaxNodeLimit=\f[R]\f[I]nodes\f[R]
! Sets the maximum number of nodes to be used during single method
! compilation.
! By default, the maximum number of nodes is set to 65,000:
! .RS
! .RS
! .PP
! \f[CB]\-XX:MaxNodeLimit=65000\f[R]
! .RE
! .RE
! .TP
! .B \f[CB]\-XX:NonNMethodCodeHeapSize=\f[R]\f[I]size\f[R]
! Sets the size in bytes of the code segment containing nonmethod code.
! .RS
! .PP
! A nonmethod code segment containing nonmethod code, such as compiler
! buffers and the bytecode interpreter.
! This code type stays in the code cache forever.
! This flag is used only if \f[CB]\-XX:SegmentedCodeCache\f[R] is enabled.
! .RE
! .TP
! .B \f[CB]\-XX:NonProfiledCodeHeapSize=\f[R]\f[I]size\f[R]
! Sets the size in bytes of the code segment containing nonprofiled
! methods.
! This flag is used only if \f[CB]\-XX:SegmentedCodeCache\f[R] is enabled.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:MaxTrivialSize=\f[R]\f[I]size\f[R]
! Sets the maximum bytecode size (in bytes) of a trivial method to be
! inlined.
! Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
! \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
! \f[CB]G\f[R] to indicate gigabytes.
! By default, the maximum bytecode size of a trivial method is set to 6
! bytes:
! .RS
! .RS
! .PP
! \f[CB]\-XX:MaxTrivialSize=6\f[R]
! .RE
! .RE
! .TP
! .B \f[CB]\-XX:+OptimizeStringConcat\f[R]
! Enables the optimization of \f[CB]String\f[R] concatenation operations.
! This option is enabled by default.
! To disable the optimization of \f[CB]String\f[R] concatenation operations,
! specify \f[CB]\-XX:\-OptimizeStringConcat\f[R].
! Only the Java HotSpot Server VM supports this option.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:+PrintAssembly\f[R]
! Enables printing of assembly code for bytecoded and native methods by
! using the external \f[CB]hsdis\-<arch>.so\f[R] or \f[CB]\&.dll\f[R] library.
! For 64\-bit VM on Windows, it\[aq]s \f[CB]hsdis\-amd64.dll\f[R].
! This lets you to see the generated code, which may help you to diagnose
! performance issues.
! .RS
! .PP
! By default, this option is disabled and assembly code isn\[aq]t printed.
! The \f[CB]\-XX:+PrintAssembly\f[R] option has to be used together with the
! \f[CB]\-XX:UnlockDiagnosticVMOptions\f[R] option that unlocks diagnostic
! JVM options.
! .RE
! .TP
! .B \f[CB]\-XX:ProfiledCodeHeapSize=\f[R]\f[I]size\f[R]
! Sets the size in bytes of the code segment containing profiled methods.
! This flag is used only if \f[CB]\-XX:SegmentedCodeCache\f[R] is enabled.
! .RS
! .RE
! .TP
! .B \f[CB]\-XX:+PrintCompilation\f[R]
! Enables verbose diagnostic output from the JVM by printing a message to
! the console every time a method is compiled.
! This lets you to see which methods actually get compiled.
! By default, this option is disabled and diagnostic output isn\[aq]t
! printed.
! .RS
  .PP
! You can also log compilation activity to a file by using the
! \f[CB]\-XX:+LogCompilation\f[R] option.
  .RE
+ .TP
+ .B \f[CB]\-XX:+PrintInlining\f[R]
+ Enables printing of inlining decisions.
+ This let\[aq]s you see which methods are getting inlined.
+ .RS
+ .PP
+ By default, this option is disabled and inlining information isn\[aq]t
+ printed.
+ The \f[CB]\-XX:+PrintInlining\f[R] option has to be used together with the
+ \f[CB]\-XX:+UnlockDiagnosticVMOptions\f[R] option that unlocks diagnostic
+ JVM options.
+ .RE
+ .TP
+ .B \f[CB]\-XX:ReservedCodeCacheSize=\f[R]\f[I]size\f[R]
+ Sets the maximum code cache size (in bytes) for JIT\-compiled code.
+ Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
+ \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
+ \f[CB]G\f[R] to indicate gigabytes.
+ The default maximum code cache size is 240 MB; if you disable tiered
+ compilation with the option \f[CB]\-XX:\-TieredCompilation\f[R], then the
+ default size is 48 MB.
+ This option has a limit of 2 GB; otherwise, an error is generated.
+ The maximum code cache size shouldn\[aq]t be less than the initial code
+ cache size; see the option \f[CB]\-XX:InitialCodeCacheSize\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:RTMAbortRatio=\f[R]\f[I]abort_ratio\f[R]
+ Specifies the RTM abort ratio is specified as a percentage (%) of all
+ executed RTM transactions.
+ If a number of aborted transactions becomes greater than this ratio,
+ then the compiled code is deoptimized.
+ This ratio is used when the \f[CB]\-XX:+UseRTMDeopt\f[R] option is
+ enabled.
+ The default value of this option is 50.
+ This means that the compiled code is deoptimized if 50% of all
+ transactions are aborted.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:RTMRetryCount=\f[R]\f[I]number_of_retries\f[R]
+ Specifies the number of times that the RTM locking code is retried, when
+ it is aborted or busy, before falling back to the normal locking
+ mechanism.
+ The default value for this option is 5.
+ The \f[CB]\-XX:UseRTMLocking\f[R] option must be enabled.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+SegmentedCodeCache\f[R]
+ Enables segmentation of the code cache.
+ Without the \f[CB]\-XX:+SegmentedCodeCache\f[R], the code cache consists
+ of one large segment.
+ With \f[CB]\-XX:+SegmentedCodeCache\f[R], we have separate segments for
+ nonmethod, profiled method, and nonprofiled method code.
+ These segments aren\[aq]t resized at runtime.
+ The feature is enabled by default if tiered compilation is enabled
+ (\f[CB]\-XX:+TieredCompilation\f[R] ) and
+ \f[CB]\-XX:ReservedCodeCacheSize\f[R] >= 240 MB.
+ The advantages are better control of the memory footprint, reduced code
+ fragmentation, and better iTLB/iCache behavior due to improved locality.
+ iTLB/iCache is a CPU\-specific term meaning Instruction Translation
+ Lookaside Buffer (ITLB).
+ ICache is an instruction cache in theCPU.
+ The implementation of the code cache can be found in the file:
+ \f[CB]/share/vm/code/codeCache.cpp\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:StartAggressiveSweepingAt=\f[R]\f[I]percent\f[R]
+ Forces stack scanning of active methods to aggressively remove unused
+ code when only the given percentage of the code cache is free.
+ The default value is 10%.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:\-TieredCompilation\f[R]
+ Disables the use of tiered compilation.
+ By default, this option is enabled.
+ Only the Java HotSpot Server VM supports this option.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseAES\f[R]
+ Enables hardware\-based AES intrinsics for Intel, AMD, and SPARC
+ hardware.
+ Intel Westmere (2010 and newer), AMD Bulldozer (2011 and newer), and
+ SPARC (T4 and newer) are the supported hardware.
+ The \f[CB]\-XX:+UseAES\f[R] is used in conjunction with UseAESIntrinsics.
+ Flags that control intrinsics now require the option
+ \f[CB]\-XX:+UnlockDiagnosticVMOptions\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseAESIntrinsics\f[R]
+ Enables \f[CB]\-XX:+UseAES\f[R] and \f[CB]\-XX:+UseAESIntrinsics\f[R] flags
+ by default and are supported only for the Java HotSpot Server VM.
+ To disable hardware\-based AES intrinsics, specify
+ \f[CB]\-XX:\-UseAES\ \-XX:\-UseAESIntrinsics\f[R].
+ For example, to enable hardware AES, use the following flags:
+ .RS
+ .RS
+ .PP
+ \f[CB]\-XX:+UseAES\ \-XX:+UseAESIntrinsics\f[R]
+ .RE
+ .PP
+ Flags that control intrinsics now require the option
+ \f[CB]\-XX:+UnlockDiagnosticVMOptions\f[R].
+ To support UseAES and UseAESIntrinsics flags, use the \f[CB]\-server\f[R]
+ option to select the Java HotSpot Server VM.
+ These flags aren\[aq]t supported on Client VM.
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseCMoveUnconditionally\f[R]
+ Generates CMove (scalar and vector) instructions regardless of
+ profitability analysis.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseCodeCacheFlushing\f[R]
+ Enables flushing of the code cache before shutting down the compiler.
+ This option is enabled by default.
+ To disable flushing of the code cache before shutting down the compiler,
+ specify \f[CB]\-XX:\-UseCodeCacheFlushing\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseCondCardMark\f[R]
+ Enables checking if the card is already marked before updating the card
+ table.
+ This option is disabled by default.
+ It should be used only on machines with multiple sockets, where it
+ increases the performance of Java applications that rely on concurrent
+ operations.
+ Only the Java HotSpot Server VM supports this option.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseCountedLoopSafepoints\f[R]
+ Keeps safepoints in counted loops.
+ Its default value is false.\ 
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseFMA\f[R]
+ Enables hardware\-based FMA intrinsics for hardware where FMA
+ instructions are available (such as, Intel, SPARC, and ARM64).
+ FMA intrinsics are generated for the
+ \f[CB]java.lang.Math.fma(\f[R]\f[I]a\f[R]\f[CB],\f[R] \f[I]b\f[R]\f[CB],\f[R]
+ \f[I]c\f[R]\f[CB])\f[R] methods that calculate the value of \f[CB](\f[R]
+ \f[I]a\f[R] \f[CB]*\f[R] \f[I]b\f[R] \f[CB]+\f[R] \f[I]c\f[R] \f[CB])\f[R]
+ expressions.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseRTMDeopt\f[R]
+ Autotunes RTM locking depending on the abort ratio.
+ This ratio is specified by the \f[CB]\-XX:RTMAbortRatio\f[R] option.
+ If the number of aborted transactions exceeds the abort ratio, then the
+ method containing the lock is deoptimized and recompiled with all locks
+ as normal locks.
+ This option is disabled by default.
+ The \f[CB]\-XX:+UseRTMLocking\f[R] option must be enabled.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseRTMLocking\f[R]
+ Generates Restricted Transactional Memory (RTM) locking code for all
+ inflated locks, with the normal locking mechanism as the fallback
+ handler.
+ This option is disabled by default.
+ Options related to RTM are available only for the Java HotSpot Server VM
+ on x86 CPUs that support Transactional Synchronization Extensions (TSX).
+ .RS
+ .PP
+ RTM is part of Intel\[aq]s TSX, which is an x86 instruction set
+ extension and facilitates the creation of multithreaded applications.
+ RTM introduces the new instructions \f[CB]XBEGIN\f[R], \f[CB]XABORT\f[R],
+ \f[CB]XEND\f[R], and \f[CB]XTEST\f[R].
+ The \f[CB]XBEGIN\f[R] and \f[CB]XEND\f[R] instructions enclose a set of
+ instructions to run as a transaction.
+ If no conflict is found when running the transaction, then the memory
+ and register modifications are committed together at the \f[CB]XEND\f[R]
+ instruction.
+ The \f[CB]XABORT\f[R] instruction can be used to explicitly abort a
+ transaction and the \f[CB]XEND\f[R] instruction checks if a set of
+ instructions is being run in a transaction.
+ .PP
+ A lock on a transaction is inflated when another thread tries to access
+ the same transaction, thereby blocking the thread that didn\[aq]t
+ originally request access to the transaction.
+ RTM requires that a fallback set of operations be specified in case a
+ transaction aborts or fails.
+ An RTM lock is a lock that has been delegated to the TSX\[aq]s system.
+ .PP
+ RTM improves performance for highly contended locks with low conflict in
+ a critical region (which is code that must not be accessed by more than
+ one thread concurrently).
+ RTM also improves the performance of coarse\-grain locking, which
+ typically doesn\[aq]t perform well in multithreaded applications.
+ (Coarse\-grain locking is the strategy of holding locks for long periods
+ to minimize the overhead of taking and releasing locks, while
+ fine\-grained locking is the strategy of trying to achieve maximum
+ parallelism by locking only when necessary and unlocking as soon as
+ possible.) Also, for lightly contended locks that are used by different
+ threads, RTM can reduce false cache line sharing, also known as cache
+ line ping\-pong.
+ This occurs when multiple threads from different processors are
+ accessing different resources, but the resources share the same cache
+ line.
+ As a result, the processors repeatedly invalidate the cache lines of
+ other processors, which forces them to read from main memory instead of
+ their cache.
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseSHA\f[R]
+ Enables hardware\-based intrinsics for SHA crypto hash functions for
+ SPARC hardware.
+ The \f[CB]UseSHA\f[R] option is used in conjunction with the
+ \f[CB]UseSHA1Intrinsics\f[R], \f[CB]UseSHA256Intrinsics\f[R], and
+ \f[CB]UseSHA512Intrinsics\f[R] options.
+ .RS
+ .PP
+ The \f[CB]UseSHA\f[R] and \f[CB]UseSHA*Intrinsics\f[R] flags are enabled by
+ default, and are supported only for Java HotSpot Server VM 64\-bit on
+ SPARC T4 and newer.
+ .PP
+ This feature is applicable only when using the
+ \f[CB]sun.security.provider.Sun\f[R] provider for SHA operations.
+ Flags that control intrinsics now require the option
+ \f[CB]\-XX:+UnlockDiagnosticVMOptions\f[R].
+ .PP
+ To disable all hardware\-based SHA intrinsics, specify the
+ \f[CB]\-XX:\-UseSHA\f[R].
+ To disable only a particular SHA intrinsic, use the appropriate
+ corresponding option.
+ For example: \f[CB]\-XX:\-UseSHA256Intrinsics\f[R].
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseSHA1Intrinsics\f[R]
+ Enables intrinsics for SHA\-1 crypto hash function.
+ Flags that control intrinsics now require the option
+ \f[CB]\-XX:+UnlockDiagnosticVMOptions\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseSHA256Intrinsics\f[R]
+ Enables intrinsics for SHA\-224 and SHA\-256 crypto hash functions.
+ Flags that control intrinsics now require the option
+ \f[CB]\-XX:+UnlockDiagnosticVMOptions\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseSHA512Intrinsics\f[R]
+ Enables intrinsics for SHA\-384 and SHA\-512 crypto hash functions.
+ Flags that control intrinsics now require the option
+ \f[CB]\-XX:+UnlockDiagnosticVMOptions\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseSuperWord\f[R]
+ Enables the transformation of scalar operations into superword
+ operations.
+ Superword is a vectorization optimization.
+ This option is enabled by default.
+ To disable the transformation of scalar operations into superword
+ operations, specify \f[CB]\-XX:\-UseSuperWord\f[R].
+ Only the Java HotSpot Server VM supports this option.
+ .RS
+ .RE
+ .SH ADVANCED SERVICEABILITY OPTIONS FOR JAVA
+ .PP
+ These \f[CB]java\f[R] options provide the ability to gather system
+ information and perform extensive debugging.
+ .TP
+ .B \f[CB]\-XX:+DisableAttachMechanism\f[R]
+ Disables the mechanism that lets tools attach to the JVM.
+ By default, this option is disabled, meaning that the attach mechanism
+ is enabled and you can use diagnostics and troubleshooting tools such as
+ \f[CB]jcmd\f[R], \f[CB]jstack\f[R], \f[CB]jmap\f[R], and \f[CB]jinfo\f[R].
+ .RS
+ .RS
+ .PP
+ \f[B]Note:\f[R] The tools such as \f[B]jcmd\f[R], \f[B]jinfo\f[R],
+ \f[B]jmap\f[R], and \f[B]jstack\f[R] shipped with the JDK aren\[aq]t
+ supported when using the tools from one JDK version to troubleshoot a
+ different JDK version.
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:+ExtendedDTraceProbes\f[R]
+ \f[B]Oracle Solaris, Linux, and macOS:\f[R] Enables additional
+ \f[CB]dtrace\f[R] tool probes that affect the performance.
+ By default, this option is disabled and \f[CB]dtrace\f[R] performs only
+ standard probes.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+HeapDumpOnOutOfMemoryError\f[R]
+ Enables the dumping of the Java heap to a file in the current directory
+ by using the heap profiler (HPROF) when a
+ \f[CB]java.lang.OutOfMemoryError\f[R] exception is thrown.
+ You can explicitly set the heap dump file path and name using the
+ \f[CB]\-XX:HeapDumpPath\f[R] option.
+ By default, this option is disabled and the heap isn\[aq]t dumped when
+ an \f[CB]OutOfMemoryError\f[R] exception is thrown.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:HeapDumpPath=path\f[R]
+ Sets the path and file name for writing the heap dump provided by the
+ heap profiler (HPROF) when the \f[CB]\-XX:+HeapDumpOnOutOfMemoryError\f[R]
+ option is set.
+ By default, the file is created in the current working directory, and
+ it\[aq]s named \f[CB]java_pid<pid>.hprof\f[R] where \f[CB]<pid>\f[R] is the
+ identifier of the process that caused the error.
+ The following example shows how to set the default file explicitly
+ (\f[CB]%p\f[R] represents the current process identifier):
+ .RS
+ .RS
+ .PP
+ \f[CB]\-XX:HeapDumpPath=./java_pid%p.hprof\f[R]
+ .RE
+ .IP \[bu] 2
+ \f[B]Oracle Solaris, Linux, and macOS:\f[R] The following example shows
+ how to set the heap dump file to
+ \f[CB]/var/log/java/java_heapdump.hprof\f[R]:
+ .RS 2
+ .RS
+ .PP
+ \f[CB]\-XX:HeapDumpPath=/var/log/java/java_heapdump.hprof\f[R]
+ .RE
+ .RE
+ .IP \[bu] 2
+ \f[B]Windows:\f[R] The following example shows how to set the heap dump
+ file to \f[CB]C:/log/java/java_heapdump.log\f[R]:
+ .RS 2
+ .RS
+ .PP
+ \f[CB]\-XX:HeapDumpPath=C:/log/java/java_heapdump.log\f[R]
+ .RE
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:LogFile=\f[R]\f[I]path\f[R]
+ Sets the path and file name to where log data is written.
+ By default, the file is created in the current working directory, and
+ it\[aq]s named \f[CB]hotspot.log\f[R].
+ .RS
+ .IP \[bu] 2
+ \f[B]Oracle Solaris, Linux, and macOS:\f[R] The following example shows
+ how to set the log file to \f[CB]/var/log/java/hotspot.log\f[R]:
+ .RS 2
+ .RS
+ .PP
+ \f[CB]\-XX:LogFile=/var/log/java/hotspot.log\f[R]
+ .RE
+ .RE
+ .IP \[bu] 2
+ \f[B]Windows:\f[R] The following example shows how to set the log file to
+ \f[CB]C:/log/java/hotspot.log\f[R]:
+ .RS 2
+ .RS
+ .PP
+ \f[CB]\-XX:LogFile=C:/log/java/hotspot.log\f[R]
+ .RE
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:+PrintClassHistogram\f[R]
+ Enables printing of a class instance histogram after one of the
+ following events:
+ .RS
+ .IP \[bu] 2
+ \f[B]Oracle Solaris, Linux, and macOS:\f[R] \f[CB]Control+Break\f[R]
+ .IP \[bu] 2
+ \f[B]Windows:\f[R] \f[CB]Control+C\f[R] (\f[CB]SIGTERM\f[R])
+ .PP
+ By default, this option is disabled.
+ .PP
+ Setting this option is equivalent to running the \f[CB]jmap\ \-histo\f[R]
+ command, or the \f[CB]jcmd\f[R] \f[I]pid\f[R] \f[CB]GC.class_histogram\f[R]
+ command, where \f[I]pid\f[R] is the current Java process identifier.
+ .RE
+ .TP
+ .B \f[CB]\-XX:+PrintConcurrentLocks\f[R]
+ Enables printing of \f[CB]java.util.concurrent\f[R] locks after one of the
+ following events:
+ .RS
+ .IP \[bu] 2
+ \f[B]Oracle Solaris, Linux, and macOS:\f[R] \f[CB]Control+Break\f[R]
+ .IP \[bu] 2
+ \f[B]Windows:\f[R] \f[CB]Control+C\f[R] (\f[CB]SIGTERM\f[R])
+ .PP
+ By default, this option is disabled.
+ .PP
+ Setting this option is equivalent to running the \f[CB]jstack\ \-l\f[R]
+ command or the \f[CB]jcmd\f[R] \f[I]pid\f[R] \f[CB]Thread.print\ \-l\f[R]
+ command, where \f[I]pid\f[R] is the current Java process identifier.
+ .RE
+ .TP
+ .B \f[CB]\-XX:+PrintFlagsRanges\f[R]
+ Prints the range specified and allows automatic testing of the values.
+ See \f[B]Validate Java Virtual Machine Flag Arguments\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+PerfDataSaveToFile\f[R]
+ If enabled, saves \f[B]jstat\f[R] binary data when the Java application
+ exits.
+ This binary data is saved in a file named
+ \f[CB]hsperfdata_\f[R]\f[I]pid\f[R], where \f[I]pid\f[R] is the process
+ identifier of the Java application that you ran.
+ Use the \f[CB]jstat\f[R] command to display the performance data contained
+ in this file as follows:
+ .RS
+ .RS
+ .PP
+ \f[CB]jstat\ \-class\ file:///\f[R]\f[I]path\f[R]\f[CB]/hsperfdata_\f[R]\f[I]pid\f[R]
+ .RE
+ .RS
+ .PP
+ \f[CB]jstat\ \-gc\ file:///\f[R]\f[I]path\f[R]\f[CB]/hsperfdata_\f[R]\f[I]pid\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UsePerfData\f[R]
+ Enables the \f[CB]perfdata\f[R] feature.
+ This option is enabled by default to allow JVM monitoring and
+ performance testing.
+ Disabling it suppresses the creation of the \f[CB]hsperfdata_userid\f[R]
+ directories.
+ To disable the \f[CB]perfdata\f[R] feature, specify
+ \f[CB]\-XX:\-UsePerfData\f[R].
+ .RS
+ .RE
+ .SH ADVANCED GARBAGE COLLECTION OPTIONS FOR JAVA
+ .PP
+ These \f[CB]java\f[R] options control how garbage collection (GC) is
+ performed by the Java HotSpot VM.
+ .TP
+ .B \f[CB]\-XX:+AggressiveHeap\f[R]
+ Enables Java heap optimization.
+ This sets various parameters to be optimal for long\-running jobs with
+ intensive memory allocation, based on the configuration of the computer
+ (RAM and CPU).
+ By default, the option is disabled and the heap isn't optimized.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+AlwaysPreTouch\f[R]
+ Enables touching of every page on the Java heap during JVM
+ initialization.
+ This gets all pages into memory before entering the \f[CB]main()\f[R]
+ method.
+ The option can be used in testing to simulate a long\-running system
+ with all virtual memory mapped to physical memory.
+ By default, this option is disabled and all pages are committed as JVM
+ heap space fills.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+CMSClassUnloadingEnabled\f[R]
+ Enables class unloading when using the concurrent mark\-sweep (CMS)
+ garbage collector.
+ This option is enabled by default.
+ To disable class unloading for the CMS garbage collector, specify
+ \f[CB]\-XX:\-CMSClassUnloadingEnabled\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:CMSExpAvgFactor=\f[R]\f[I]percent\f[R]
+ Sets the percentage of time (0 to 100) used to weight the current sample
+ when computing exponential averages for the concurrent collection
+ statistics.
+ By default, the exponential averages factor is set to 25%.
+ The following example shows how to set the factor to 15%:
+ .RS
+ .RS
+ .PP
+ \f[CB]\-XX:CMSExpAvgFactor=15\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:CMSInitiatingOccupancyFraction=\f[R]\f[I]percent\f[R]
+ Sets the percentage of the old generation occupancy (0 to 100) at which
+ to start a CMS collection cycle.
+ The default value is set to \-1.
+ Any negative value (including the default) implies that the option
+ \f[CB]\-XX:CMSTriggerRatio\f[R] is used to define the value of the
+ initiating occupancy fraction.
+ .RS
+ .PP
+ The following example shows how to set the factor to 20%:
+ .IP
+ .nf
+ \f[CB]
+ >\ \ \ `\-XX:CMSInitiatingOccupancyFraction=20`
+ \f[R]
+ .fi
+ .RE
+ .TP
+ .B \f[CB]\-XX:CMSIncrementalDutySafetyFactor=\f[R]\f[I]percent\f[R]
+ Sets the percentage (0 to 100) used to add conservatism when computing
+ the duty cycle.
+ The default value is 10.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+CMSScavengeBeforeRemark\f[R]
+ Enables scavenging attempts before the CMS remark step.
+ By default, this option is disabled.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:CMSTriggerRatio=percent\f[R]
+ Sets the percentage (0 to 100) of the value specified by the option
+ \f[CB]\-XX:MinHeapFreeRatio\f[R] that\[aq]s allocated before a CMS
+ collection cycle commences.
+ The default value is set to 80%.
+ .RS
  .PP
! The following example shows how to set the occupancy fraction to 75%:
! .RS
  .PP
! \f[CB]\-XX:CMSTriggerRatio=75\f[R]
  .RE
  .RE
+ .TP
+ .B \f[CB]\-XX:ConcGCThreads=\f[R]\f[I]threads\f[R]
+ Sets the number of threads used for concurrent GC.
+ Sets \f[I]\f[CI]threads\f[I]\f[R] to approximately 1/4 of the number of
+ parallel garbage collection threads.
+ The default value depends on the number of CPUs available to the JVM.
+ .RS
+ .PP
+ For example, to set the number of threads for concurrent GC to 2,
+ specify the following option:
+ .RS
+ .PP
+ \f[CB]\-XX:ConcGCThreads=2\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:+DisableExplicitGC\f[R]
+ Enables the option that disables processing of calls to the
+ \f[CB]System.gc()\f[R] method.
+ This option is disabled by default, meaning that calls to
+ \f[CB]System.gc()\f[R] are processed.
+ If processing of calls to \f[CB]System.gc()\f[R] is disabled, then the JVM
+ still performs GC when necessary.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+ExplicitGCInvokesConcurrent\f[R]
+ Enables invoking of concurrent GC by using the \f[CB]System.gc()\f[R]
+ request.
+ This option is disabled by default and can be enabled only with the
+ deprecated \f[CB]\-XX:+UseConcMarkSweepGC\f[R] option and the
+ \f[CB]\-XX:+UseG1GC\f[R] option.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+ExplicitGCInvokesConcurrentAndUnloadsClasses\f[R]
+ Enables invoking of concurrent GC by using the \f[CB]System.gc()\f[R]
+ request and unloading of classes during the concurrent GC cycle.
+ This option is disabled by default and can be enabled only with the
+ deprecated \f[CB]\-XX:+UseConcMarkSweepGC\f[R] option.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:G1HeapRegionSize=size\f[R]
+ Sets the size of the regions into which the Java heap is subdivided when
+ using the garbage\-first (G1) collector.
+ The value is a power of 2 and can range from 1 MB to 32 MB.
+ The goal is to have around 2048 regions based on the minimum Java heap
+ size.
+ The default region size is determined ergonomically based on the heap
+ size.
+ .RS
+ .PP
+ The following example sets the size of the subdivisions to 16 MB:
+ .RS
+ .PP
+ \f[CB]\-XX:G1HeapRegionSize=16m\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:G1HeapWastePercent=\f[R]\f[I]percent\f[R]
+ Sets the percentage of heap that you\[aq]re willing to waste.
+ The Java HotSpot VM doesn\[aq]t initiate the mixed garbage collection
+ cycle when the reclaimable percentage is less than the heap waste
+ percentage.
+ The default is 5 percent.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:G1MaxNewSizePercent=\f[R]\f[I]percent\f[R]
+ Sets the percentage of the heap size to use as the maximum for the young
+ generation size.
+ The default value is 60 percent of your Java heap.
+ .RS
+ .PP
+ This is an experimental flag.
+ This setting replaces the \f[CB]\-XX:DefaultMaxNewGenPercent\f[R] setting.
+ .PP
+ This setting isn\[aq]t available in Java HotSpot VM build 23 or earlier.
+ .RE
+ .TP
+ .B \f[CB]\-XX:G1MixedGCCountTarget=\f[R]\f[I]number\f[R]
+ Sets the target number of mixed garbage collections after a marking
+ cycle to collect old regions with at most
+ \f[CB]G1MixedGCLIveThresholdPercent\f[R] live data.
+ The default is 8 mixed garbage collections.
+ The goal for mixed collections is to be within this target number.
+ .RS
+ .PP
+ This setting isn\[aq]t available in Java HotSpot VM build 23 or earlier.
+ .RE
+ .TP
+ .B \f[CB]\-XX:G1MixedGCLiveThresholdPercent=\f[R]\f[I]percent\f[R]
+ Sets the occupancy threshold for an old region to be included in a mixed
+ garbage collection cycle.
+ The default occupancy is 85 percent.
+ .RS
+ .PP
+ This is an experimental flag.
+ This setting replaces the
+ \f[CB]\-XX:G1OldCSetRegionLiveThresholdPercent\f[R] setting.
+ .PP
+ This setting isn\[aq]t available in Java HotSpot VM build 23 or earlier.
+ .RE
+ .TP
+ .B \f[CB]\-XX:G1NewSizePercent=\f[R]\f[I]percent\f[R]
+ Sets the percentage of the heap to use as the minimum for the young
+ generation size.
+ The default value is 5 percent of your Java heap.
+ .RS
+ .PP
+ This is an experimental flag.
+ This setting replaces the \f[CB]\-XX:DefaultMinNewGenPercent\f[R] setting.
+ .PP
+ This setting isn\[aq]t available in Java HotSpot VM build 23 or earlier.
+ .RE
+ .TP
+ .B \f[CB]\-XX:G1OldCSetRegionThresholdPercent=\f[R]\f[I]percent\f[R]
+ Sets an upper limit on the number of old regions to be collected during
+ a mixed garbage collection cycle.
+ The default is 10 percent of the Java heap.
+ .RS
+ .PP
+ This setting isn\[aq]t available in Java HotSpot VM build 23 or earlier.
+ .RE
+ .TP
+ .B \f[CB]\-XX:G1ReservePercent=\f[R]\f[I]percent\f[R]
+ Sets the percentage of the heap (0 to 50) that\[aq]s reserved as a false
+ ceiling to reduce the possibility of promotion failure for the G1
+ collector.
+ When you increase or decrease the percentage, ensure that you adjust the
+ total Java heap by the same amount.
+ By default, this option is set to 10%.
+ .RS
+ .PP
+ The following example sets the reserved heap to 20%:
+ .RS
+ .PP
+ \f[CB]\-XX:G1ReservePercent=20\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:InitialHeapOccupancyPercent=\f[R]\f[I]percent\f[R]
+ Sets the Java heap occupancy threshold that triggers a marking cycle.
+ The default occupancy is 45 percent of the entire Java heap.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:InitialHeapSize=\f[R]\f[I]size\f[R]
+ Sets the initial size (in bytes) of the memory allocation pool.
+ This value must be either 0, or a multiple of 1024 and greater than 1
+ MB.
+ Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
+ \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
+ \f[CB]G\f[R] to indicate gigabytes.
+ The default value is selected at run time based on the system
+ configuration.
+ .RS
+ .PP
+ The following examples show how to set the size of allocated memory to 6
+ MB using various units:
+ .IP
+ .nf
+ \f[CB]
+ \-XX:InitialHeapSize=6291456
+ \-XX:InitialHeapSize=6144k
+ \-XX:InitialHeapSize=6m
+ \f[R]
+ .fi
+ .PP
+ If you set this option to 0, then the initial size is set as the sum of
+ the sizes allocated for the old generation and the young generation.
+ The size of the heap for the young generation can be set using the
+ \f[CB]\-XX:NewSize\f[R] option.
+ .RE
+ .TP
+ .B \f[CB]\-XX:InitialSurvivorRatio=\f[R]\f[I]ratio\f[R]
+ Sets the initial survivor space ratio used by the throughput garbage
+ collector (which is enabled by the \f[CB]\-XX:+UseParallelGC\f[R] and/or
+ \f[CB]\-XX:+UseParallelOldGC\f[R] options).
+ Adaptive sizing is enabled by default with the throughput garbage
+ collector by using the \f[CB]\-XX:+UseParallelGC\f[R] and
+ \f[CB]\-XX:+UseParallelOldGC\f[R] options, and the survivor space is
+ resized according to the application behavior, starting with the initial
+ value.
+ If adaptive sizing is disabled (using the
+ \f[CB]\-XX:\-UseAdaptiveSizePolicy\f[R] option), then the
+ \f[CB]\-XX:SurvivorRatio\f[R] option should be used to set the size of the
+ survivor space for the entire execution of the application.
+ .RS
+ .PP
+ The following formula can be used to calculate the initial size of
+ survivor space (S) based on the size of the young generation (Y), and
+ the initial survivor space ratio (R):
+ .RS
+ .PP
+ \f[CB]S=Y/(R+2)\f[R]
+ .RE
+ .PP
+ The 2 in the equation denotes two survivor spaces.
+ The larger the value specified as the initial survivor space ratio, the
+ smaller the initial survivor space size.
+ .PP
+ By default, the initial survivor space ratio is set to 8.
+ If the default value for the young generation space size is used (2 MB),
+ then the initial size of the survivor space is 0.2 MB.
+ .PP
+ The following example shows how to set the initial survivor space ratio
+ to 4:
+ .RS
+ .PP
+ \f[CB]\-XX:InitialSurvivorRatio=4\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:InitiatingHeapOccupancyPercent=\f[R]\f[I]percent\f[R]
+ Sets the percentage of the heap occupancy (0 to 100) at which to start a
+ concurrent GC cycle.
+ It\[aq]s used by garbage collectors that trigger a concurrent GC cycle
+ based on the occupancy of the entire heap, not just one of the
+ generations (for example, the G1 garbage collector).
+ .RS
+ .PP
+ By default, the initiating value is set to 45%.
+ A value of 0 implies nonstop GC cycles.
+ The following example shows how to set the initiating heap occupancy to
+ 75%:
+ .RS
+ .PP
+ \f[CB]\-XX:InitiatingHeapOccupancyPercent=75\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:MaxGCPauseMillis=\f[R]\f[I]time\f[R]
+ Sets a target for the maximum GC pause time (in milliseconds).
+ This is a soft goal, and the JVM will make its best effort to achieve
+ it.
+ The specified value doesn\[aq]t adapt to your heap size.
+ By default, there\[aq]s no maximum pause time value.
+ .RS
+ .PP
+ The following example shows how to set the maximum target pause time to
+ 500 ms:
+ .RS
+ .PP
+ \f[CB]\-XX:MaxGCPauseMillis=500\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:MaxHeapSize=\f[R]\f[I]size\f[R]
+ Sets the maximum size (in byes) of the memory allocation pool.
+ This value must be a multiple of 1024 and greater than 2 MB.
+ Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
+ \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
+ \f[CB]G\f[R] to indicate gigabytes.
+ The default value is selected at run time based on the system
+ configuration.
+ For server deployments, the options \f[CB]\-XX:InitialHeapSize\f[R] and
+ \f[CB]\-XX:MaxHeapSize\f[R] are often set to the same value.
+ .RS
+ .PP
+ The following examples show how to set the maximum allowed size of
+ allocated memory to 80 MB using various units:
+ .IP
+ .nf
+ \f[CB]
+ \-XX:MaxHeapSize=83886080
+ \-XX:MaxHeapSize=81920k
+ \-XX:MaxHeapSize=80m
+ \f[R]
+ .fi
+ .PP
+ On Oracle Solaris 7 and Oracle Solaris 8 SPARC platforms, the upper
+ limit for this value is approximately 4,000 MB minus overhead amounts.
+ On Oracle Solaris 2.6 and x86 platforms, the upper limit is
+ approximately 2,000 MB minus overhead amounts.
+ On Linux platforms, the upper limit is approximately 2,000 MB minus
+ overhead amounts.
+ .PP
+ The \f[CB]\-XX:MaxHeapSize\f[R] option is equivalent to \f[CB]\-Xmx\f[R].
+ .RE
+ .TP
+ .B \f[CB]\-XX:MaxHeapFreeRatio=\f[R]\f[I]percent\f[R]
+ Sets the maximum allowed percentage of free heap space (0 to 100) after
+ a GC event.
+ If free heap space expands above this value, then the heap is shrunk.
+ By default, this value is set to 70%.
+ .RS
+ .PP
+ Minimize the Java heap size by lowering the values of the parameters
+ \f[CB]MaxHeapFreeRatio\f[R] (default value is 70%) and
+ \f[CB]MinHeapFreeRatio\f[R] (default value is 40%) with the command\-line
+ options \f[CB]\-XX:MaxHeapFreeRatio\f[R] and
+ \f[CB]\-XX:MinHeapFreeRatio\f[R].
+ Lowering \f[CB]MaxHeapFreeRatio\f[R] to as low as 10% and
+ \f[CB]MinHeapFreeRatio\f[R] to 5% has successfully reduced the heap size
+ without too much performance regression; however, results may vary
+ greatly depending on your application.
+ Try different values for these parameters until they\[aq]re as low as
+ possible yet still retain acceptable performance.
+ .RS
+ .PP
+ \f[CB]\-XX:MaxHeapFreeRatio=10\ \-XX:MinHeapFreeRatio=5\f[R]
+ .RE
+ .PP
+ Customers trying to keep the heap small should also add the option
+ \f[CB]\-XX:\-ShrinkHeapInSteps\f[R].
+ See \f[B]Performance Tuning Examples\f[R] for a description of using this
+ option to keep the Java heap small by reducing the dynamic footprint for
+ embedded applications.
+ .RE
+ .TP
+ .B \f[CB]\-XX:MaxMetaspaceSize=\f[R]\f[I]size\f[R]
+ Sets the maximum amount of native memory that can be allocated for class
+ metadata.
+ By default, the size isn\[aq]t limited.
+ The amount of metadata for an application depends on the application
+ itself, other running applications, and the amount of memory available
+ on the system.
+ .RS
+ .PP
+ The following example shows how to set the maximum class metadata size
+ to 256 MB:
+ .RS
+ .PP
+ \f[CB]\-XX:MaxMetaspaceSize=256m\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:MaxNewSize=\f[R]\f[I]size\f[R]
+ Sets the maximum size (in bytes) of the heap for the young generation
+ (nursery).
+ The default value is set ergonomically.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:MaxTenuringThreshold=\f[R]\f[I]threshold\f[R]
+ Sets the maximum tenuring threshold for use in adaptive GC sizing.
+ The largest value is 15.
+ The default value is 15 for the parallel (throughput) collector, and 6
+ for the CMS collector.
+ .RS
+ .PP
+ The following example shows how to set the maximum tenuring threshold to
+ 10:
+ .RS
+ .PP
+ \f[CB]\-XX:MaxTenuringThreshold=10\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:MetaspaceSize=\f[R]\f[I]size\f[R]
+ Sets the size of the allocated class metadata space that triggers a
+ garbage collection the first time it\[aq]s exceeded.
+ This threshold for a garbage collection is increased or decreased
+ depending on the amount of metadata used.
+ The default size depends on the platform.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:MinHeapFreeRatio=\f[R]\f[I]percent\f[R]
+ Sets the minimum allowed percentage of free heap space (0 to 100) after
+ a GC event.
+ If free heap space falls below this value, then the heap is expanded.
+ By default, this value is set to 40%.
+ .RS
+ .PP
+ Minimize Java heap size by lowering the values of the parameters
+ \f[CB]MaxHeapFreeRatio\f[R] (default value is 70%) and
+ \f[CB]MinHeapFreeRatio\f[R] (default value is 40%) with the command\-line
+ options \f[CB]\-XX:MaxHeapFreeRatio\f[R] and
+ \f[CB]\-XX:MinHeapFreeRatio\f[R].
+ Lowering \f[CB]MaxHeapFreeRatio\f[R] to as low as 10% and
+ \f[CB]MinHeapFreeRatio\f[R] to 5% has successfully reduced the heap size
+ without too much performance regression; however, results may vary
+ greatly depending on your application.
+ Try different values for these parameters until they\[aq]re as low as
+ possible, yet still retain acceptable performance.
+ .RS
+ .PP
+ \f[CB]\-XX:MaxHeapFreeRatio=10\ \-XX:MinHeapFreeRatio=5\f[R]
+ .RE
+ .PP
+ Customers trying to keep the heap small should also add the option
+ \f[CB]\-XX:\-ShrinkHeapInSteps\f[R].
+ See \f[B]Performance Tuning Examples\f[R] for a description of using this
+ option to keep the Java heap small by reducing the dynamic footprint for
+ embedded applications.
+ .RE
+ .TP
+ .B \f[CB]\-XX:NewRatio=\f[R]\f[I]ratio\f[R]
+ Sets the ratio between young and old generation sizes.
+ By default, this option is set to 2.
+ The following example shows how to set the young\-to\-old ratio to 1:
+ .RS
+ .RS
+ .PP
+ \f[CB]\-XX:NewRatio=1\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:NewSize=\f[R]\f[I]size\f[R]
+ Sets the initial size (in bytes) of the heap for the young generation
+ (nursery).
+ Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
+ \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
+ \f[CB]G\f[R] to indicate gigabytes.
+ .RS
+ .PP
+ The young generation region of the heap is used for new objects.
+ GC is performed in this region more often than in other regions.
+ If the size for the young generation is too low, then a large number of
+ minor GCs are performed.
+ If the size is too high, then only full GCs are performed, which can
+ take a long time to complete.
+ It is recommended that you keep the size for the young generation
+ greater than 25% and less than 50% of the overall heap size.
+ .PP
+ The following examples show how to set the initial size of the young
+ generation to 256 MB using various units:
+ .IP
+ .nf
+ \f[CB]
+ \-XX:NewSize=256m
+ \-XX:NewSize=262144k
+ \-XX:NewSize=268435456
+ \f[R]
+ .fi
+ .PP
+ The \f[CB]\-XX:NewSize\f[R] option is equivalent to \f[CB]\-Xmn\f[R].
+ .RE
+ .TP
+ .B \f[CB]\-XX:ParallelGCThreads=\f[R]\f[I]threads\f[R]
+ Sets the value of the stop\-the\-world (STW) worker threads.
+ This option sets the value of \f[I]threads\f[R] to the number of logical
+ processors.
+ The value of \f[I]threads\f[R] is the same as the number of logical
+ processors up to a value of 8.
+ .RS
+ .PP
+ If there are more than 8 logical processors, then this option sets the
+ value of \f[I]threads\f[R] to approximately 5/8 of the logical
+ processors.
+ This works in most cases except for larger SPARC systems where the value
+ of \f[I]threads\f[R] can be approximately 5/16 of the logical processors.
+ .PP
+ The default value depends on the number of CPUs available to the JVM.
+ .PP
+ For example, to set the number of threads for parallel GC to 2, specify
+ the following option:
+ .RS
+ .PP
+ \f[CB]\-XX:ParallelGCThreads=2\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:+ParallelRefProcEnabled\f[R]
+ Enables parallel reference processing.
+ By default, this option is disabled.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+PrintAdaptiveSizePolicy\f[R]
+ Enables printing of information about adaptive\-generation sizing.
+ By default, this option is disabled.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+ScavengeBeforeFullGC\f[R]
+ Enables GC of the young generation before each full GC.
+ This option is enabled by default.
+ It is recommended that you \f[I]don\[aq]t\f[R] disable it, because
+ scavenging the young generation before a full GC can reduce the number
+ of objects reachable from the old generation space into the young
+ generation space.
+ To disable GC of the young generation before each full GC, specify the
+ option \f[CB]\-XX:\-ScavengeBeforeFullGC\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:SoftRefLRUPolicyMSPerMB=\f[R]\f[I]time\f[R]
+ Sets the amount of time (in milliseconds) a softly reachable object is
+ kept active on the heap after the last time it was referenced.
+ The default value is one second of lifetime per free megabyte in the
+ heap.
+ The \f[CB]\-XX:SoftRefLRUPolicyMSPerMB\f[R] option accepts integer values
+ representing milliseconds per one megabyte of the current heap size (for
+ Java HotSpot Client VM) or the maximum possible heap size (for Java
+ HotSpot Server VM).
+ This difference means that the Client VM tends to flush soft references
+ rather than grow the heap, whereas the Server VM tends to grow the heap
+ rather than flush soft references.
+ In the latter case, the value of the \f[CB]\-Xmx\f[R] option has a
+ significant effect on how quickly soft references are garbage collected.
+ .RS
+ .PP
+ The following example shows how to set the value to 2.5 seconds:
+ .PP
+ \f[CB]\-XX:SoftRefLRUPolicyMSPerMB=2500\f[R]
+ .RE
+ .TP
+ .B \f[CB]\-XX:\-ShrinkHeapInSteps\f[R]
+ Incrementally reduces the Java heap to the target size, specified by the
+ option \f[CB]\-XX:MaxHeapFreeRatio\f[R].
+ This option is enabled by default.
+ If disabled, then it immediately reduces the Java heap to the target
+ size instead of requiring multiple garbage collection cycles.
+ Disable this option if you want to minimize the Java heap size.
+ You will likely encounter performance degradation when this option is
+ disabled.
+ .RS
+ .PP
+ See \f[B]Performance Tuning Examples\f[R] for a description of using the
+ \f[CB]MaxHeapFreeRatio\f[R] option to keep the Java heap small by reducing
+ the dynamic footprint for embedded applications.
+ .RE
+ .TP
+ .B \f[CB]\-XX:StringDeduplicationAgeThreshold=\f[R]\f[I]threshold\f[R]
+ Identifies \f[CB]String\f[R] objects reaching the specified age that are
+ considered candidates for deduplication.
+ An object\[aq]s age is a measure of how many times it has survived
+ garbage collection.
+ This is sometimes referred to as tenuring.
+ .RS
+ .RS
+ .PP
+ \f[B]Note:\f[R] \f[CB]String\f[R] objects that are promoted to an old heap
+ region before this age has been reached are always considered candidates
+ for deduplication.
+ The default value for this option is \f[CB]3\f[R].
+ See the \f[CB]\-XX:+UseStringDeduplication\f[R] option.
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:SurvivorRatio=\f[R]\f[I]ratio\f[R]
+ Sets the ratio between eden space size and survivor space size.
+ By default, this option is set to 8.
+ The following example shows how to set the eden/survivor space ratio to
+ 4:
+ .RS
+ .RS
+ .PP
+ \f[CB]\-XX:SurvivorRatio=4\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:TargetSurvivorRatio=\f[R]\f[I]percent\f[R]
+ Sets the desired percentage of survivor space (0 to 100) used after
+ young garbage collection.
+ By default, this option is set to 50%.
+ .RS
+ .PP
+ The following example shows how to set the target survivor space ratio
+ to 30%:
+ .RS
+ .PP
+ \f[CB]\-XX:TargetSurvivorRatio=30\f[R]
+ .RE
+ .RE
+ .TP
+ .B \f[CB]\-XX:TLABSize=\f[R]\f[I]size\f[R]
+ Sets the initial size (in bytes) of a thread\-local allocation buffer
+ (TLAB).
+ Append the letter \f[CB]k\f[R] or \f[CB]K\f[R] to indicate kilobytes,
+ \f[CB]m\f[R] or \f[CB]M\f[R] to indicate megabytes, or \f[CB]g\f[R] or
+ \f[CB]G\f[R] to indicate gigabytes.
+ If this option is set to 0, then the JVM selects the initial size
+ automatically.
+ .RS
  .PP
! The following example shows how to set the initial TLAB size to 512 KB:
! .RS
  .PP
! \f[CB]\-XX:TLABSize=512k\f[R]
  .RE
  .RE
+ .TP
+ .B \f[CB]\-XX:+UseAdaptiveSizePolicy\f[R]
+ Enables the use of adaptive generation sizing.
+ This option is enabled by default.
+ To disable adaptive generation sizing, specify
+ \f[CB]\-XX:\-UseAdaptiveSizePolicy\f[R] and set the size of the memory
+ allocation pool explicitly.
+ See the \f[CB]\-XX:SurvivorRatio\f[R] option.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseCMSInitiatingOccupancyOnly\f[R]
+ Enables the use of the occupancy value as the only criterion for
+ initiating the CMS collector.
+ By default, this option is disabled and other criteria may be used.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseG1GC\f[R]
+ Enables the use of the garbage\-first (G1) garbage collector.
+ It\[aq]s a server\-style garbage collector, targeted for multiprocessor
+ machines with a large amount of RAM.
+ This option meets GC pause time goals with high probability, while
+ maintaining good throughput.
+ The G1 collector is recommended for applications requiring large heaps
+ (sizes of around 6 GB or larger) with limited GC latency requirements (a
+ stable and predictable pause time below 0.5 seconds).
+ By default, this option is enabled and G1 is used as the default garbage
+ collector.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseGCOverheadLimit\f[R]
+ Enables the use of a policy that limits the proportion of time spent by
+ the JVM on GC before an \f[CB]OutOfMemoryError\f[R] exception is thrown.
+ This option is enabled, by default, and the parallel GC will throw an
+ \f[CB]OutOfMemoryError\f[R] if more than 98% of the total time is spent on
+ garbage collection and less than 2% of the heap is recovered.
+ When the heap is small, this feature can be used to prevent applications
+ from running for long periods of time with little or no progress.
+ To disable this option, specify the option
+ \f[CB]\-XX:\-UseGCOverheadLimit\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseNUMA\f[R]
+ Enables performance optimization of an application on a machine with
+ nonuniform memory architecture (NUMA) by increasing the
+ application\[aq]s use of lower latency memory.
+ By default, this option is disabled and no optimization for NUMA is
+ made.
+ The option is available only when the parallel garbage collector is used
+ (\f[CB]\-XX:+UseParallelGC\f[R]).
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseParallelGC\f[R]
+ Enables the use of the parallel scavenge garbage collector (also known
+ as the throughput collector) to improve the performance of your
+ application by leveraging multiple processors.
+ .RS
+ .PP
+ By default, this option is disabled and the default collector is used.
+ If it\[aq]s enabled, then the \f[CB]\-XX:+UseParallelOldGC\f[R] option is
+ automatically enabled, unless you explicitly disable it.
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseParallelOldGC\f[R]
+ Enables the use of the parallel garbage collector for full GCs.
+ By default, this option is disabled.
+ Enabling it automatically enables the \f[CB]\-XX:+UseParallelGC\f[R]
+ option.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseSerialGC\f[R]
+ Enables the use of the serial garbage collector.
+ This is generally the best choice for small and simple applications that
+ don\[aq]t require any special functionality from garbage collection.
+ By default, this option is disabled and the default collector is used.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseSHM\f[R]
+ \f[B]Linux only:\f[R] Enables the JVM to use shared memory to set up
+ large pages.
+ .RS
+ .PP
+ See \f[B]Large Pages\f[R] for setting up large pages.
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseStringDeduplication\f[R]
+ Enables string deduplication.
+ By default, this option is disabled.
+ To use this option, you must enable the garbage\-first (G1) garbage
+ collector.
+ .RS
  .PP
! String deduplication reduces the memory footprint of \f[CB]String\f[R]
! objects on the Java heap by taking advantage of the fact that many
! \f[CB]String\f[R] objects are identical.
! Instead of each \f[CB]String\f[R] object pointing to its own character
! array, identical \f[CB]String\f[R] objects can point to and share the same
! character array.
! .RE
! .TP
! .B \f[CB]\-XX:+UseTLAB\f[R]
! Enables the use of thread\-local allocation blocks (TLABs) in the young
! generation space.
! This option is enabled by default.
! To disable the use of TLABs, specify the option \f[CB]\-XX:\-UseTLAB\f[R].
! .RS
! .RE
! .SH DEPRECATED JAVA OPTIONS
! .PP
! These \f[CB]java\f[R] options are deprecated and might be removed in a
! future JDK release.
! They\[aq]re still accepted and acted upon, but a warning is issued when
! they\[aq]re used.
! .TP
! .B \f[CB]\-Xfuture\f[R]
! Enables strict class\-file format checks that enforce close conformance
! to the class\-file format specification.
! Developers should use this flag when developing new code.
! Stricter checks may become the default in future releases.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xloggc:\f[R]\f[I]filename\f[R]
! Sets the file to which verbose GC events information should be
! redirected for logging.
! The \f[CB]\-Xloggc\f[R] option overrides \f[CB]\-verbose:gc\f[R] if both are
! given with the same java command.
! \f[CB]\-Xloggc:\f[R]\f[I]filename\f[R] is replaced by
! \f[CB]\-Xlog:gc:\f[R]\f[I]filename\f[R].
! See Enable Logging with the JVM Unified Logging Framework.
! .RS
  .PP
! Example:
  .PP
! \f[CB]\-Xlog:gc:garbage\-collection.log\f[R]
  .RE
+ .TP
+ .B \f[CB]\-XX:+FailOverToOldVerifier\f[R]
+ Enables automatic failover to the old verifier when the new type checker
+ fails.
+ By default, this option is disabled and it\[aq]s ignored (that is,
+ treated as disabled) for classes with a recent bytecode version.
+ You can enable it only for classes with older versions of the bytecode.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:+TraceClassLoading\f[R]
+ Enables tracing of classes as they are loaded.
+ By default, this option is disabled and classes aren\[aq]t traced.
+ .RS
+ .PP
+ The replacement Unified Logging syntax is
+ \f[CB]\-Xlog:class+load=\f[R]\f[I]level\f[R].
+ See \f[B]Enable Logging with the JVM Unified Logging Framework\f[R]
+ .PP
+ Use \f[I]level\f[R]=\f[CB]info\f[R] for regular information, or
+ \f[I]level\f[R]=\f[CB]debug\f[R] for additional information.
+ In Unified Logging syntax, \f[CB]\-verbose:class\f[R] equals
+ \f[CB]\-Xlog:class+load=info,class+unload=info\f[R].
+ .RE
+ .TP
+ .B \f[CB]\-XX:+TraceClassLoadingPreorder\f[R]
+ Enables tracing of all loaded classes in the order in which they\[aq]re
+ referenced.
+ By default, this option is disabled and classes aren\[aq]t traced.
+ .RS
+ .PP
+ The replacement Unified Logging syntax is
+ \f[CB]\-Xlog:class+preorder=debug\f[R].
+ See \f[B]Enable Logging with the JVM Unified Logging Framework\f[R].
+ .RE
+ .TP
+ .B \f[CB]\-XX:+TraceClassResolution\f[R]
+ Enables tracing of constant pool resolutions.
+ By default, this option is disabled and constant pool resolutions
+ aren\[aq]t traced.
+ .RS
+ .PP
+ The replacement Unified Logging syntax is
+ \f[CB]\-Xlog:class+resolve=debug\f[R].
+ See \f[B]Enable Logging with the JVM Unified Logging Framework\f[R].
+ .RE
+ .TP
+ .B \f[CB]\-XX:+TraceLoaderConstraints\f[R]
+ Enables tracing of the loader constraints recording.
+ By default, this option is disabled and loader constraints recording
+ isn\[aq]t traced.
+ .RS
+ .PP
+ The replacement Unified Logging syntax is
+ \f[CB]\-Xlog:class+loader+constraints=info\f[R].
+ See \f[B]Enable Logging with the JVM Unified Logging Framework\f[R].
+ .RE
+ .TP
+ .B \f[CB]\-XX:+UseConcMarkSweepGC\f[R]
+ Enables the use of the CMS garbage collector for the old generation.
+ CMS is an alternative to the default garbage collector (G1), which also
+ focuses on meeting application latency requirements.
+ By default, this option is disabled and the collector is selected
+ automatically based on the configuration of the machine and type of the
+ JVM.
+ The CMS garbage collector is deprecated.
+ .RS
+ .RE
+ .SH OBSOLETE JAVA OPTIONS
+ .PP
+ These \f[CB]java\f[R] options are still accepted but ignored, and a
+ warning is issued when they\[aq]re used.
+ .TP
+ .B \f[CB]\-XX:+UseMembar\f[R]
+ Enabled issuing membars on thread\-state transitions.
+ This option was disabled by default on all platforms except ARM servers,
+ where it was enabled.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:MaxPermSize=\f[R]\f[I]size\f[R]
+ Sets the maximum permanent generation space size (in bytes).
+ This option was deprecated in JDK 8 and superseded by the
+ \f[CB]\-XX:MaxMetaspaceSize\f[R] option.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-XX:PermSize=\f[R]\f[I]size\f[R]
+ Sets the space (in bytes) allocated to the permanent generation that
+ triggers a garbage collection if it\[aq]s exceeded.
+ This option was deprecated in JDK 8 and superseded by the
+ \f[CB]\-XX:MetaspaceSize\f[R] option.
+ .RS
+ .RE
+ .SH REMOVED JAVA OPTIONS
+ .PP
+ These \f[CB]java\f[R] options have been removed in JDK 13 and using them
+ results in an error of:
+ .RS
+ .PP
+ \f[CB]Unrecognized\ VM\ option\f[R] \f[I]option\-name\f[R]
+ .RE
+ .TP
+ .B \f[CB]\-XX:+AggressiveOpts\f[R]
+ Enabled the use of aggressive performance optimization features.
+ By default, this option was disabled and experimental performance
+ features were not used.
+ .RS
+ .RE
+ .PP
+ For the lists and descriptions of options removed in previous releases
+ see the \f[I]Removed Java Options\f[R] section in:
+ .IP \[bu] 2
+ \f[B]Java Platform, Standard Edition Tools Reference, Release 12\f[R]
+ [https://docs.oracle.com/en/java/javase/12/tools/java.html#GUID\-3B1CE181\-CD30\-4178\-9602\-230B800D4FAE]
+ .IP \[bu] 2
+ \f[B]Java Platform, Standard Edition Tools Reference, Release 11\f[R]
+ [https://docs.oracle.com/en/java/javase/11/tools/java.html#GUID\-741FC470\-AA3E\-494A\-8D2B\-1B1FE4A990D1]
+ .IP \[bu] 2
+ \f[B]Java Platform, Standard Edition Tools Reference, Release 10\f[R]
+ [https://docs.oracle.com/javase/10/tools/java.htm#JSWOR624]
+ .IP \[bu] 2
+ \f[B]Java Platform, Standard Edition Tools Reference, Release 9\f[R]
+ [https://docs.oracle.com/javase/9/tools/java.htm#JSWOR624]
+ .IP \[bu] 2
+ \f[B]Java Platform, Standard Edition Tools Reference, Release 8 for
+ Oracle JDK on Windows\f[R]
+ [https://docs.oracle.com/javase/8/docs/technotes/tools/windows/java.html#BGBCIEFC]
+ .IP \[bu] 2
+ \f[B]Java Platform, Standard Edition Tools Reference, Release 8 for
+ Oracle JDK on Solaris, Linux, and macOS\f[R]
+ [https://docs.oracle.com/javase/8/docs/technotes/tools/unix/java.html#BGBCIEFC]
+ .SH JAVA COMMAND\-LINE ARGUMENT FILES
+ .PP
+ You can shorten or simplify the \f[CB]java\f[R] command by using
+ \f[CB]\@\f[R] argument files to specify one or more text files that
+ contain arguments, such as options and class names, which are passed to
+ the \f[CB]java\f[R] command.
+ This let\[aq]s you to create \f[CB]java\f[R] commands of any length on any
+ operating system.
+ .PP
+ In the command line, use the at sign (\f[CB]\@\f[R]) prefix to identify an
+ argument file that contains \f[CB]java\f[R] options and class names.
+ When the \f[CB]java\f[R] command encounters a file beginning with the at
+ sign (\f[CB]\@\f[R]), it expands the contents of that file into an
+ argument list just as they would be specified on the command line.
+ .PP
+ The \f[CB]java\f[R] launcher expands the argument file contents until it
+ encounters the \f[CB]\-Xdisable\-\@files\f[R] option.
+ You can use the \f[CB]\-Xdisable\-\@files\f[R] option anywhere on the
+ command line, including in an argument file, to stop \f[CB]\@\f[R]
+ argument files expansion.
+ .PP
+ The following items describe the syntax of \f[CB]java\f[R] argument files:
+ .IP \[bu] 2
+ The argument file must contain only ASCII characters or characters in
+ system default encoding that\[aq]s ASCII friendly, such as UTF\-8.
+ .IP \[bu] 2
+ The argument file size must not exceed MAXINT (2,147,483,647) bytes.
+ .IP \[bu] 2
+ The launcher doesn\[aq]t expand wildcards that are present within an
+ argument file.
+ .IP \[bu] 2
+ Use white space or new line characters to separate arguments included in
+ the file.
+ .IP \[bu] 2
+ White space includes a white space character, \f[CB]\\t\f[R],
+ \f[CB]\\n\f[R], \f[CB]\\r\f[R], and \f[CB]\\f\f[R].
+ .RS 2
+ .PP
+ For example, it is possible to have a path with a space, such as
+ \f[CB]c:\\Program\ Files\f[R] that can be specified as either
+ \f[CB]"c:\\\\Program\ Files"\f[R] or, to avoid an escape,
+ \f[CB]c:\\Program"\ "Files\f[R].
+ .RE
+ .IP \[bu] 2
+ Any option that contains spaces, such as a path component, must be
+ within quotation marks using quotation (\[aq]"\[aq]) characters in its
+ entirety.
+ .IP \[bu] 2
+ A string within quotation marks may contain the characters \f[CB]\\n\f[R],
+ \f[CB]\\r\f[R], \f[CB]\\t\f[R], and \f[CB]\\f\f[R].
+ They are converted to their respective ASCII codes.
+ \ 
+ .IP \[bu] 2
+ If a file name contains embedded spaces, then put the whole file name in
+ double quotation marks.
+ .IP \[bu] 2
+ File names in an argument file are relative to the current directory,
+ not to the location of the argument file.
+ .IP \[bu] 2
+ Use the number sign \f[CB]#\f[R] in the argument file to identify
+ comments.
+ All characters following the \f[CB]#\f[R] are ignored until the end of
+ line.
+ .IP \[bu] 2
+ Additional at sign \f[CB]\@\f[R] prefixes to \f[CB]\@\f[R] prefixed options
+ act as an escape, (the first \f[CB]\@\f[R] is removed and the rest of the
+ arguments are presented to the launcher literally).
+ .IP \[bu] 2
+ Lines may be continued using the continuation character (\f[CB]\\\f[R]) at
+ the end\-of\-line.
+ The two lines are concatenated with the leading white spaces trimmed.
+ To prevent trimming the \ leading white spaces, a continuation character
+ (\f[CB]\\\f[R]) may be placed at the first column.
+ .IP \[bu] 2
+ Because backslash (\\) is an escape character, a backslash
+ character\ must be escaped with another backslash character.
+ .IP \[bu] 2
+ Partial quote is allowed and is closed by an end\-of\-file.
+ .IP \[bu] 2
+ An open quote stops at end\-of\-line unless \f[CB]\\\f[R] is the last
+ character, which then joins the next line by removing all leading white
+ space characters.
+ .IP \[bu] 2
+ Wildcards (*) aren\[aq]t allowed in these lists (such as specifying
+ \f[CB]*.java\f[R]).
+ .IP \[bu] 2
+ Use of the at sign (\f[CB]\@\f[R]) to recursively interpret files
+ isn\[aq]t supported.
+ .SS Example of Open or Partial Quotes in an Argument File
+ .PP
+ In the argument file,
+ .IP
+ .nf
+ \f[CB]
+ \-cp\ "lib/
+ cool/
+ app/
+ jars
+ \f[R]
+ .fi
+ .PP
+ this is interpreted as:
+ .RS
+ .PP
+ \f[CB]\-cp\ lib/cool/app/jars\f[R]
+ .RE
+ .SS Example of a Backslash Character\ Escaped with Another Backslash
+ Character in an Argument File
+ .PP
+ To output the following:
+ .RS
+ .PP
+ \f[CB]\-cp\ c:\\Program\ Files\ (x86)\\Java\\jre\\lib\\ext;c:\\Program\ Files\\Java\\jre9\\lib\\ext\f[R]
+ .RE
+ .PP
+ The backslash character must be specified in the argument file as:
+ .RS
+ .PP
+ \f[CB]\-cp\ \ "c:\\\\Program\ Files\ (x86)\\\\Java\\\\jre\\\\lib\\\\ext;c:\\\\Program\ Files\\\\Java\\\\jre9\\\\lib\\\\ext"\f[R]
+ .RE
+ .SS Example of an EOL Escape Used to Force Concatenation of Lines in an
+ Argument File
+ .PP
+ In the argument file,
+ .IP
+ .nf
+ \f[CB]
+ \-cp\ "/lib/cool\ app/jars:\\
+ \ \ \ \ /lib/another\ app/jars"
+ \f[R]
+ .fi
+ .PP
+ This is interpreted as:
+ .RS
+ .PP
+ \f[CB]\-cp\ /lib/cool\ app/jars:/lib/another\ app/jars\f[R]
+ .RE
+ .SS Example of Line Continuation with Leading Spaces in an Argument File
+ .PP
+ In the argument file,
+ .IP
+ .nf
+ \f[CB]
+ \-cp\ "/lib/cool\\
+ \\app/jars”
+ \f[R]
+ .fi
+ .PP
+ This is interpreted as:
+ .PP
+ \f[CB]\-cp\ /lib/cool\ app/jars\f[R]
+ .SS Examples of Using Single Argument File
+ .PP
+ You can use a single argument file, such as \f[CB]myargumentfile\f[R] in
+ the following example, to hold all required \f[CB]java\f[R] arguments:
+ .RS
+ .PP
+ \f[CB]java\ \@myargumentfile\f[R]
+ .RE
+ .SS Examples of Using Argument Files with Paths
+ .PP
+ You can include relative paths in argument files; however, they\[aq]re
+ relative to the current working directory and not to the paths of the
+ argument files themselves.
+ In the following example, \f[CB]path1/options\f[R] and
+ \f[CB]path2/options\f[R] represent argument files with different paths.
+ Any relative paths that they contain are relative to the current working
+ directory and not to the argument files:
+ .RS
+ .PP
+ \f[CB]java\ \@path1/options\ \@path2/classes\f[R]
+ .RE
+ .SH CODE HEAP STATE ANALYTICS
+ .SS Overview
+ .PP
+ There are occasions when having insight into the current state of the
+ JVM code heap would be helpful to answer questions such as:
+ .IP \[bu] 2
+ Why was the JIT turned off and then on again and again?
+ .IP \[bu] 2
+ Where has all the code heap space gone?
+ .IP \[bu] 2
+ Why is the method sweeper not working effectively?
+ .PP
+ To provide this insight, a code heap state analytics feature has been
+ implemented that enables on\-the\-fly analysis of the code heap.
+ The analytics process is divided into two parts.
+ The first part examines the entire code heap and aggregates all
+ information that is believed to be useful or important.
+ The second part consists of several independent steps that print the
+ collected information with an emphasis on different aspects of the data.
+ Data collection and printing are done on an "on request" basis.
+ .SS Syntax
+ .PP
+ Requests for real\-time, on\-the\-fly analysis can be issued with the
+ following command:
+ .RS
+ .PP
+ \f[CB]jcmd\f[R] \f[I]pid\f[R] \f[CB]Compiler.CodeHeap_Analytics\f[R]
+ [\f[I]function\f[R]] [\f[I]granularity\f[R]]
+ .RE
+ .PP
+ If you are only interested in how the code heap looks like after running
+ a sample workload, you can use the command line option:
+ .RS
+ .PP
+ \f[CB]\-Xlog:codecache=Trace\f[R]
+ .RE
+ .PP
+ To see the code heap state when a "CodeCache full" condition exists,
+ start the VM with the command line option:
+ .RS
+ .PP
+ \f[CB]\-Xlog:codecache=Debug\f[R]
+ .RE
+ .PP
+ See \f[B]CodeHeap State Analytics (OpenJDK)\f[R]
+ [https://bugs.openjdk.java.net/secure/attachment/75649/JVM_CodeHeap_StateAnalytics_V2.pdf]
+ for a detailed description of the code heap state analytics feature, the
+ supported functions, and the granularity options.
+ .SH ENABLE LOGGING WITH THE JVM UNIFIED LOGGING FRAMEWORK
+ .PP
+ You use the \f[CB]\-Xlog\f[R] option to configure or enable logging with
+ the Java Virtual Machine (JVM) unified logging framework.
+ .SS Synopsis
+ .RS
+ .PP
+ \f[CB]\-Xlog\f[R][\f[CB]:\f[R][\f[I]what\f[R]][\f[CB]:\f[R][\f[I]output\f[R]][\f[CB]:\f[R][\f[I]decorators\f[R]][\f[CB]:\f[R]\f[I]output\-options\f[R][\f[CB],\f[R]...]]]]]
+ .RE
+ .TP
+ .B \f[I]what\f[R]
+ Specifies a combination of tags and levels of the form
+ \f[I]tag1\f[R][\f[CB]+\f[R]\f[I]tag2\f[R]...][\f[CB]*\f[R]][\f[CB]=\f[R]\f[I]level\f[R]][\f[CB],\f[R]...].
+ Unless the wildcard (\f[CB]*\f[R]) is specified, only log messages tagged
+ with exactly the tags specified are matched.
+ See \f[B]\-Xlog Tags and Levels\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[I]output\f[R]
+ Sets the type of output.
+ Omitting the \f[I]output\f[R] type defaults to \f[CB]stdout\f[R].
+ See \f[B]\-Xlog Output\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[I]decorators\f[R]
+ Configures the output to use a custom set of decorators.
+ Omitting \f[I]decorators\f[R] defaults to \f[CB]uptime\f[R],
+ \f[CB]level\f[R], and \f[CB]tags\f[R].
+ See \f[B]Decorations\f[R].
+ .RS
+ .RE
+ .TP
+ .B \f[I]output\-options\f[R]
+ Sets the \f[CB]\-Xlog\f[R] logging output options.
+ .RS
+ .RE
+ .SS Description
+ .PP
+ The Java Virtual Machine (JVM) unified logging framework provides a
+ common logging system for all components of the JVM.
+ GC logging for the JVM has been changed to use the new logging
+ framework.
+ The mapping of old GC flags to the corresponding new Xlog configuration
+ is described in \f[B]Convert GC Logging Flags to Xlog\f[R].
+ In addition, runtime logging has also been changed to use the JVM
+ unified logging framework.
+ The mapping of legacy runtime logging flags to the corresponding new
+ Xlog configuration is described in \f[B]Convert Runtime Logging Flags to
+ Xlog\f[R].
+ .PP
+ The following provides quick reference to the \f[CB]\-Xlog\f[R] command
+ and syntax for options:
+ .TP
+ .B \f[CB]\-Xlog\f[R]
+ Enables JVM logging on an \f[CB]info\f[R] level.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-Xlog:help\f[R]
+ Prints \f[CB]\-Xlog\f[R] usage syntax and available tags, levels, and
+ decorators along with example command lines with explanations.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-Xlog:disable\f[R]
+ Turns off all logging and clears all configuration of the logging
+ framework including the default configuration for warnings and errors.
+ .RS
+ .RE
+ .TP
+ .B \f[CB]\-Xlog\f[R][\f[CB]:\f[R]\f[I]option\f[R]]
+ Applies multiple arguments in the order that they appear on the command
+ line.
+ Multiple \f[CB]\-Xlog\f[R] arguments for the same output override each
+ other in their given order.
+ .RS
+ .PP
+ The \f[I]option\f[R] is set as:
+ .RS
+ .PP
+ [\f[I]tag\-selection\f[R]][\f[CB]:\f[R][\f[I]output\f[R]][\f[CB]:\f[R][\f[I]decorators\f[R]][\f[CB]:\f[R]\f[I]output\-options\f[R]]]]
+ .RE
+ .PP
+ Omitting the \f[I]tag\-selection\f[R] defaults to a tag\-set of
+ \f[CB]all\f[R] and a level of \f[CB]info\f[R].
+ .RS
+ .PP
+ \f[I]tag\f[R][\f[CB]+\f[R]...] \f[CB]all\f[R]
+ .RE
+ .PP
+ The \f[CB]all\f[R] tag is a meta tag consisting of all tag\-sets
+ available.
+ The asterisk \f[CB]*\f[R] in a tag set definition denotes a wildcard tag
+ match.
+ Matching with a wildcard selects all tag sets that contain \f[I]at
+ least\f[R] the specified tags.
+ Without the wildcard, only exact matches of the specified tag sets are
+ selected.
+ .PP
+ \f[I]output\-options\f[R] is
+ .RS
+ .PP
+ \f[CB]filecount=\f[R]\f[I]file\-count\f[R] \f[CB]filesize=\f[R]\f[I]file size
+ with optional K, M or G suffix\f[R]
+ .RE
+ .RE
+ .SS Default Configuration
+ .PP
+ When the \f[CB]\-Xlog\f[R] option and nothing else is specified on the
+ command line, the default configuration is used.
+ The default configuration logs all messages with a level that matches
+ either warning or error regardless of what tags the message is
+ associated with.
+ The default configuration is equivalent to entering the following on the
+ command line:
+ .RS
+ .PP
+ \f[CB]\-Xlog:all=warning:stdout:uptime,level,tags\f[R]
+ .RE
+ .SS Controlling Logging at Runtime
+ .PP
+ Logging can also be controlled at run time through Diagnostic Commands
+ (with the \f[B]jcmd\f[R] utility).
+ Everything that can be specified on the command line can also be
+ specified dynamically with the \f[CB]VM.log\f[R] command.
+ As the diagnostic commands are automatically exposed as MBeans, you can
+ use JMX to change logging configuration at run time.
+ .SS \-Xlog Tags and Levels
+ .PP
+ Each log message has a level and a tag set associated with it.
+ The level of the message corresponds to its details, and the tag set
+ corresponds to what the message contains or which JVM component it
+ involves (such as, \f[CB]gc\f[R], \f[CB]jit\f[R], or \f[CB]os\f[R]).
+ Mapping GC flags to the Xlog configuration is described in \f[B]Convert
+ GC Logging Flags to Xlog\f[R].
+ Mapping legacy runtime logging flags to the corresponding Xlog
+ configuration is described in \f[B]Convert Runtime Logging Flags to
+ Xlog\f[R].
+ .PP
+ \f[B]Available log levels:\f[R]
+ .IP \[bu] 2
+ \f[CB]off\f[R]
+ .IP \[bu] 2
+ \f[CB]trace\f[R]
+ .IP \[bu] 2
+ \f[CB]debug\f[R]
+ .IP \[bu] 2
+ \f[CB]info\f[R]
+ .IP \[bu] 2
+ \f[CB]warning\f[R]
+ .IP \[bu] 2
+ \f[CB]error\f[R]
+ .PP
+ \f[B]Available log tags:\f[R]
+ .PP
+ There are literally dozens of log tags, which in the right combinations,
+ will enable a range of logging output.
+ The full set of available log tags can be seen using
+ \f[CB]\-Xlog:help\f[R].
+ Specifying \f[CB]all\f[R] instead of a tag combination matches all tag
+ combinations.
+ .SS \-Xlog Output
+ .PP
+ The \f[CB]\-Xlog\f[R] option supports the following types of outputs:
+ .IP \[bu] 2
+ \f[CB]stdout\f[R] \-\-\- Sends output to stdout
+ .IP \[bu] 2
+ \f[CB]stderr\f[R] \-\-\- Sends output to stderr
+ .IP \[bu] 2
+ \f[CB]file=\f[R]\f[I]filename\f[R] \-\-\- Sends output to text file(s).
+ .PP
+ When using \f[CB]file=\f[R]\f[I]filename\f[R], specifying \f[CB]%p\f[R]
+ and/or \f[CB]%t\f[R] in the file name expands to the JVM\[aq]s PID and
+ startup timestamp, respectively.
+ You can also configure text files to handle file rotation based on file
+ size and a number of files to rotate.
+ For example, to rotate the log file every 10 MB and keep 5 files in
+ rotation, specify the options \f[CB]filesize=10M,\ filecount=5\f[R].
+ The target size of the files isn\[aq]t guaranteed to be exact, it\[aq]s
+ just an approximate value.
+ Files are rotated by default with up to 5 rotated files of target size
+ 20 MB, unless configured otherwise.
+ Specifying \f[CB]filecount=0\f[R] means that the log file shouldn\[aq]t be
+ rotated.
+ There\[aq]s a possibility of the pre\-existing log file getting
+ overwritten.
+ .SS Decorations
+ .PP
+ Logging messages are decorated with information about the message.
+ You can configure each output to use a custom set of decorators.
+ The order of the output is always the same as listed in the table.
+ You can configure the decorations to be used at run time.
+ Decorations are prepended to the log message.
+ For example:
+ .IP
+ .nf
+ \f[CB]
+ [6.567s][info][gc,old]\ Old\ collection\ complete
+ \f[R]
+ .fi
+ .PP
+ Omitting \f[CB]decorators\f[R] defaults to \f[CB]uptime\f[R],
+ \f[CB]level\f[R], and \f[CB]tags\f[R].
+ The \f[CB]none\f[R] decorator is special and is used to turn off all
+ decorations.
+ .PP
+ \f[CB]time\f[R] (\f[CB]t\f[R]), \f[CB]utctime\f[R] (\f[CB]utc\f[R]),
+ \f[CB]uptime\f[R] (\f[CB]u\f[R]), \f[CB]timemillis\f[R] (\f[CB]tm\f[R]),
+ \f[CB]uptimemillis\f[R] (\f[CB]um\f[R]), \f[CB]timenanos\f[R] (\f[CB]tn\f[R]),
+ \f[CB]uptimenanos\f[R] (\f[CB]un\f[R]), \f[CB]hostname\f[R] (\f[CB]hn\f[R]),
+ \f[CB]pid\f[R] (\f[CB]p\f[R]), \f[CB]tid\f[R] (\f[CB]ti\f[R]), \f[CB]level\f[R]
+ (\f[CB]l\f[R]), \f[CB]tags\f[R] (\f[CB]tg\f[R]) decorators can also be
+ specified as \f[CB]none\f[R] for no decoration.
  .PP
! .TS
! tab(@);
! lw(14.9n) lw(55.1n).
! T{
! Decorations
! T}@T{
! Description
! T}
! _
! T{
! \f[CB]time\f[R] or \f[CB]t\f[R]
! T}@T{
! Current time and date in ISO\-8601 format.
! T}
! T{
! \f[CB]utctime\f[R] or \f[CB]utc\f[R]
! T}@T{
! Universal Time Coordinated or Coordinated Universal Time.
! T}
! T{
! \f[CB]uptime\f[R] or \f[CB]u\f[R]
! T}@T{
! Time since the start of the JVM in seconds and milliseconds.
! For example, 6.567s.
! T}
! T{
! \f[CB]timemillis\f[R] or \f[CB]tm\f[R]
! T}@T{
! The same value as generated by \f[CB]System.currentTimeMillis()\f[R]
! T}
! T{
! \f[CB]uptimemillis\f[R] or \f[CB]um\f[R]
! T}@T{
! Milliseconds since the JVM started.
! T}
! T{
! \f[CB]timenanos\f[R] or \f[CB]tn\f[R]
! T}@T{
! The same value generated by \f[CB]System.nanoTime()\f[R].
! T}
! T{
! \f[CB]uptimenanos\f[R] or \f[CB]un\f[R]
! T}@T{
! Nanoseconds since the JVM started.
! T}
! T{
! \f[CB]hostname\f[R] or \f[CB]hn\f[R]
! T}@T{
! The host name.
! T}
! T{
! \f[CB]pid\f[R] or \f[CB]p\f[R]
! T}@T{
! The process identifier.
! T}
! T{
! \f[CB]tid\f[R] or \f[CB]ti\f[R]
! T}@T{
! The thread identifier.
! T}
! T{
! \f[CB]level\f[R] or \f[CB]l\f[R]
! T}@T{
! The level associated with the log message.
! T}
! T{
! \f[CB]tags\f[R] or \f[CB]tg\f[R]
! T}@T{
! The tag\-set associated with the log message.
! T}
! .TE
! .SS Convert GC Logging Flags to Xlog
  .PP
! .TS
! tab(@);
! lw(22.4n) lw(16.5n) lw(31.2n).
! T{
! Legacy Garbage Collection (GC) Flag
! T}@T{
! Xlog Configuration
! T}@T{
! Comment
! T}
! _
! T{
! \f[CB]G1PrintHeapRegions\f[R]
! T}@T{
! \f[CB]\-Xlog:gc+region=trace\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]GCLogFileSize\f[R]
! T}@T{
! No configuration available
! T}@T{
! Log rotation is handled by the framework.
! T}
! T{
! \f[CB]NumberOfGCLogFiles\f[R]
! T}@T{
! Not Applicable
! T}@T{
! Log rotation is handled by the framework.
! T}
! T{
! \f[CB]PrintAdaptiveSizePolicy\f[R]
! T}@T{
! \f[CB]\-Xlog:gc+ergo*=\f[R]\f[I]level\f[R]
! T}@T{
! Use a \f[I]level\f[R] of \f[CB]debug\f[R] for most of the information, or a
! \f[I]level\f[R] of \f[CB]trace\f[R] for all of what was logged for
! \f[CB]PrintAdaptiveSizePolicy\f[R].
! T}
! T{
! \f[CB]PrintGC\f[R]
! T}@T{
! \f[CB]\-Xlog:gc\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]PrintGCApplicationConcurrentTime\f[R]
! T}@T{
! \f[CB]\-Xlog:safepoint\f[R]
! T}@T{
! Note that \f[CB]PrintGCApplicationConcurrentTime\f[R] and
! \f[CB]PrintGCApplicationStoppedTime\f[R] are logged on the same tag and
! aren\[aq]t separated in the new logging.
! T}
! T{
! \f[CB]PrintGCApplicationStoppedTime\f[R]
! T}@T{
! \f[CB]\-Xlog:safepoint\f[R]
! T}@T{
! Note that \f[CB]PrintGCApplicationConcurrentTime\f[R] and
! \f[CB]PrintGCApplicationStoppedTime\f[R] are logged on the same tag and
! not separated in the new logging.
! T}
! T{
! \f[CB]PrintGCCause\f[R]
! T}@T{
! Not Applicable
! T}@T{
! GC cause is now always logged.
! T}
! T{
! \f[CB]PrintGCDateStamps\f[R]
! T}@T{
! Not Applicable
! T}@T{
! Date stamps are logged by the framework.
! T}
! T{
! \f[CB]PrintGCDetails\f[R]
! T}@T{
! \f[CB]\-Xlog:gc*\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]PrintGCID\f[R]
! T}@T{
! Not Applicable
! T}@T{
! GC ID is now always logged.
! T}
! T{
! \f[CB]PrintGCTaskTimeStamps\f[R]
! T}@T{
! \f[CB]\-Xlog:gc+task*=debug\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]PrintGCTimeStamps\f[R]
! T}@T{
! Not Applicable
! T}@T{
! Time stamps are logged by the framework.
! T}
! T{
! \f[CB]PrintHeapAtGC\f[R]
! T}@T{
! \f[CB]\-Xlog:gc+heap=trace\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]PrintReferenceGC\f[R]
! T}@T{
! \f[CB]\-Xlog:gc+ref*=debug\f[R]
! T}@T{
! Note that in the old logging, \f[CB]PrintReferenceGC\f[R] had an effect
! only if \f[CB]PrintGCDetails\f[R] was also enabled.
! T}
! T{
! \f[CB]PrintStringDeduplicationStatistics\f[R]
! T}@T{
! `\-Xlog:gc+stringdedup*=debug
! T}@T{
! ` Not Applicable
! T}
! T{
! \f[CB]PrintTenuringDistribution\f[R]
! T}@T{
! \f[CB]\-Xlog:gc+age*=\f[R]\f[I]level\f[R]
! T}@T{
! Use a \f[I]level\f[R] of \f[CB]debug\f[R] for the most relevant
! information, or a \f[I]level\f[R] of \f[CB]trace\f[R] for all of what was
! logged for \f[CB]PrintTenuringDistribution\f[R].
! T}
! T{
! \f[CB]UseGCLogFileRotation\f[R]
! T}@T{
! Not Applicable
! T}@T{
! What was logged for \f[CB]PrintTenuringDistribution\f[R].
! T}
! .TE
! .SS Convert Runtime Logging Flags to Xlog
  .PP
! .TS
! tab(@);
! lw(15.0n) lw(20.2n) lw(34.7n).
! T{
! Legacy Runtime Flag
! T}@T{
! Xlog Configuration
! T}@T{
! Comment
! T}
! _
! T{
! \f[CB]TraceExceptions\f[R]
! T}@T{
! \f[CB]\-Xlog:exceptions=info\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]TraceClassLoading\f[R]
! T}@T{
! \f[CB]\-Xlog:class+load=\f[R]\f[I]level\f[R]
! T}@T{
! Use \f[I]level\f[R]=\f[CB]info\f[R] for regular information, or
! \f[I]level\f[R]=\f[CB]debug\f[R] for additional information.
! In Unified Logging syntax, \f[CB]\-verbose:class\f[R] equals
! \f[CB]\-Xlog:class+load=info,class+unload=info\f[R].
! T}
! T{
! \f[CB]TraceClassLoadingPreorder\f[R]
! T}@T{
! \f[CB]\-Xlog:class+preorder=debug\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]TraceClassUnloading\f[R]
! T}@T{
! \f[CB]\-Xlog:class+unload=\f[R]\f[I]level\f[R]
! T}@T{
! Use \f[I]level\f[R]=\f[CB]info\f[R] for regular information, or
! \f[I]level\f[R]=\f[CB]trace\f[R] for additional information.
! In Unified Logging syntax, \f[CB]\-verbose:class\f[R] equals
! \f[CB]\-Xlog:class+load=info,class+unload=info\f[R].
! T}
! T{
! \f[CB]VerboseVerification\f[R]
! T}@T{
! \f[CB]\-Xlog:verification=info\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]TraceClassPaths\f[R]
! T}@T{
! \f[CB]\-Xlog:class+path=info\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]TraceClassResolution\f[R]
! T}@T{
! \f[CB]\-Xlog:class+resolve=debug\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]TraceClassInitialization\f[R]
! T}@T{
! \f[CB]\-Xlog:class+init=info\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]TraceLoaderConstraints\f[R]
! T}@T{
! \f[CB]\-Xlog:class+loader+constraints=info\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]TraceClassLoaderData\f[R]
! T}@T{
! \f[CB]\-Xlog:class+loader+data=\f[R]\f[I]level\f[R]
! T}@T{
! Use \f[I]level\f[R]=\f[CB]debug\f[R] for regular information or
! \f[I]level\f[R]=\f[CB]trace\f[R] for additional information.
! T}
! T{
! \f[CB]TraceSafepointCleanupTime\f[R]
! T}@T{
! \f[CB]\-Xlog:safepoint+cleanup=info\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]TraceSafepoint\f[R]
! T}@T{
! \f[CB]\-Xlog:safepoint=debug\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]TraceMonitorInflation\f[R]
! T}@T{
! \f[CB]\-Xlog:monitorinflation=debug\f[R]
! T}@T{
! Not Applicable
! T}
! T{
! \f[CB]TraceBiasedLocking\f[R]
! T}@T{
! \f[CB]\-Xlog:biasedlocking=\f[R]\f[I]level\f[R]
! T}@T{
! Use \f[I]level\f[R]=\f[CB]info\f[R] for regular information, or
! \f[I]level\f[R]=\f[CB]trace\f[R] for additional information.
! T}
! T{
! \f[CB]TraceRedefineClasses\f[R]
! T}@T{
! \f[CB]\-Xlog:redefine+class*=\f[R]\f[I]level\f[R]
! T}@T{
! \f[I]level\f[R]=\f[CB]info\f[R], \f[CB]debug\f[R], and \f[CB]trace\f[R] provide
! increasing amounts of information.
! T}
! .TE
! .SS \-Xlog Usage Examples
  .PP
! The following are \f[CB]\-Xlog\f[R] examples.
! .TP
! .B \f[CB]\-Xlog\f[R]
! Logs all messages by using the \f[CB]info\f[R] level to \f[CB]stdout\f[R]
! with \f[CB]uptime\f[R], \f[CB]levels\f[R], and \f[CB]tags\f[R] decorations.
! This is equivalent to using:
! .RS
! .RS
! .PP
! \f[CB]\-Xlog:all=info:stdout:uptime,levels,tags\f[R]
! .RE
! .RE
! .TP
! .B \f[CB]\-Xlog:gc\f[R]
! Logs messages tagged with the \f[CB]gc\f[R] tag using \f[CB]info\f[R] level
! to \f[CB]stdout\f[R].
! The default configuration for all other messages at level
! \f[CB]warning\f[R] is in effect.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xlog:gc,safepoint\f[R]
! Logs messages tagged either with the \f[CB]gc\f[R] or \f[CB]safepoint\f[R]
! tags, both using the \f[CB]info\f[R] level, to \f[CB]stdout\f[R], with
! default decorations.
! Messages tagged with both \f[CB]gc\f[R] and \f[CB]safepoint\f[R] won\[aq]t
! be logged.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xlog:gc+ref=debug\f[R]
! Logs messages tagged with both \f[CB]gc\f[R] and \f[CB]ref\f[R] tags, using
! the \f[CB]debug\f[R] level to \f[CB]stdout\f[R], with default decorations.
! Messages tagged only with one of the two tags won\[aq]t be logged.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xlog:gc=debug:file=gc.txt:none\f[R]
! Logs messages tagged with the \f[CB]gc\f[R] tag using the \f[CB]debug\f[R]
! level to a file called \f[CB]gc.txt\f[R] with no decorations.
! The default configuration for all other messages at level
! \f[CB]warning\f[R] is still in effect.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xlog:gc=trace:file=gctrace.txt:uptimemillis,pids:filecount=5,filesize=1024\f[R]
! Logs messages tagged with the \f[CB]gc\f[R] tag using the \f[CB]trace\f[R]
! level to a rotating file set with 5 files with size 1 MB with the base
! name \f[CB]gctrace.txt\f[R] and uses decorations \f[CB]uptimemillis\f[R] and
! \f[CB]pid\f[R].
! .RS
! .PP
! The default configuration for all other messages at level
! \f[CB]warning\f[R] is still in effect.
! .RE
! .TP
! .B \f[CB]\-Xlog:gc::uptime,tid\f[R]
! Logs messages tagged with the \f[CB]gc\f[R] tag using the default
! \[aq]info\[aq] level to default the output \f[CB]stdout\f[R] and uses
! decorations \f[CB]uptime\f[R] and \f[CB]tid\f[R].
! The default configuration for all other messages at level
! \f[CB]warning\f[R] is still in effect.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xlog:gc*=info,safepoint*=off\f[R]
! Logs messages tagged with at least \f[CB]gc\f[R] using the \f[CB]info\f[R]
! level, but turns off logging of messages tagged with \f[CB]safepoint\f[R].
! Messages tagged with both \f[CB]gc\f[R] and \f[CB]safepoint\f[R] won\[aq]t
! be logged.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xlog:disable\ \-Xlog:safepoint=trace:safepointtrace.txt\f[R]
! Turns off all logging, including warnings and errors, and then enables
! messages tagged with \f[CB]safepoint\f[R]using \f[CB]trace\f[R]level to the
! file \f[CB]safepointtrace.txt\f[R].
! The default configuration doesn\[aq]t apply, because the command line
! started with \f[CB]\-Xlog:disable\f[R].
! .RS
! .RE
! .SS Complex \-Xlog Usage Examples
! .PP
! The following describes a few complex examples of using the
! \f[CB]\-Xlog\f[R] option.
! .TP
! .B \f[CB]\-Xlog:gc+class*=debug\f[R]
! Logs messages tagged with at least \f[CB]gc\f[R] and \f[CB]class\f[R] tags
! using the \f[CB]debug\f[R] level to \f[CB]stdout\f[R].
! The default configuration for all other messages at the level
! \f[CB]warning\f[R] is still in effect
! .RS
! .RE
! .TP
! .B \f[CB]\-Xlog:gc+meta*=trace,class*=off:file=gcmetatrace.txt\f[R]
! Logs messages tagged with at least the \f[CB]gc\f[R] and \f[CB]meta\f[R]
! tags using the \f[CB]trace\f[R] level to the file \f[CB]metatrace.txt\f[R]
! but turns off all messages tagged with \f[CB]class\f[R].
! Messages tagged with \f[CB]gc\f[R], \f[CB]meta\f[R], and \f[CB]class\f[R]
! aren\[aq]t be logged as \f[CB]class*\f[R] is set to off.
! The default configuration for all other messages at level
! \f[CB]warning\f[R] is in effect except for those that include
! \f[CB]class\f[R].
! .RS
! .RE
! .TP
! .B \f[CB]\-Xlog:gc+meta=trace\f[R]
! Logs messages tagged with exactly the \f[CB]gc\f[R] and \f[CB]meta\f[R] tags
! using the \f[CB]trace\f[R] level to \f[CB]stdout\f[R].
! The default configuration for all other messages at level
! \f[CB]warning\f[R] is still be in effect.
! .RS
! .RE
! .TP
! .B \f[CB]\-Xlog:gc+class+heap*=debug,meta*=warning,threads*=off\f[R]
! Logs messages tagged with at least \f[CB]gc\f[R], \f[CB]class\f[R], and
! \f[CB]heap\f[R] tags using the \f[CB]trace\f[R] level to \f[CB]stdout\f[R] but
! only log messages tagged with \f[CB]meta\f[R] with level.
! The default configuration for all other messages at the level
! \f[CB]warning\f[R] is in effect except for those that include
! \f[CB]threads\f[R].
! .RS
! .RE
! .SH VALIDATE JAVA VIRTUAL MACHINE FLAG ARGUMENTS
! .PP
! You use values provided to all Java Virtual Machine (JVM) command\-line
! flags for validation and, if the input value is invalid or
! out\-of\-range, then an appropriate error message is displayed.
! .PP
! Whether they\[aq]re set ergonomically, in a command line, by an input
! tool, or through the APIs (for example, classes contained in the package
! \f[CB]java.lang.management\f[R]) the values provided to all Java Virtual
! Machine (JVM) command\-line flags are validated.
! Ergonomics are described in Java Platform, Standard Edition HotSpot
! Virtual Machine Garbage Collection Tuning Guide.
! .PP
! Range and constraints are validated either when all flags have their
! values set during JVM initialization or a flag\[aq]s value is changed
! during runtime (for example using the \f[CB]jcmd\f[R] tool).
! The JVM is terminated if a value violates either the range or constraint
! check and an appropriate error message is printed on the error stream.
! .PP
! For example, if a flag violates a range or a constraint check, then the
! JVM exits with an error:
! .IP
! .nf
! \f[CB]
! java\ \-XX:AllocatePrefetchStyle=5\ \-version\ \ \ 
! intx\ AllocatePrefetchStyle=5\ is\ outside\ the\ allowed\ range\ [\ 0\ ...\ 3\ ]\ \ \ 
! Improperly\ specified\ VM\ option\ \[aq]AllocatePrefetchStyle=5\[aq]\ \ \ 
! Error:\ Could\ not\ create\ the\ Java\ Virtual\ Machine.\ \ 
! Error:\ A\ fatal\ exception\ has\ occurred.\ Program\ will\ exit.
! \f[R]
! .fi
! .PP
! The flag \f[CB]\-XX:+PrintFlagsRanges\f[R] prints the range of all the
! flags.
! This flag allows automatic testing of the flags by the values provided
! by the ranges.
! For the flags that have the ranges specified, the type, name, and the
! actual range is printed in the output.
! .PP
! For example,
! .IP
! .nf
! \f[CB]
! intx\ \ \ ThreadStackSize\ [\ 0\ ...\ 9007199254740987\ ]\ {pd\ product}
! \f[R]
! .fi
! .PP
! For the flags that don\[aq]t have the range specified, the values
! aren\[aq]t displayed in the print out.
! For example:
! .IP
! .nf
! \f[CB]
! size_t\ NewSize\ \ \ \ \ \ \ \ \ [\ \ \ ...\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ ]\ {product}
! \f[R]
! .fi
! .PP
! This helps to identify the flags that need to be implemented.
! The automatic testing framework can skip those flags that don\[aq]t have
! values and aren\[aq]t implemented.
! .SH LARGE PAGES
! .PP
! You use large pages, also known as huge pages, as memory pages that are
! significantly larger than the standard memory page size (which varies
! depending on the processor and operating system).
! Large pages optimize processor Translation\-Lookaside Buffers.
! .PP
! A Translation\-Lookaside Buffer (TLB) is a page translation cache that
! holds the most\-recently used virtual\-to\-physical address
! translations.
! A TLB is a scarce system resource.
! A TLB miss can be costly because the processor must then read from the
! hierarchical page table, which may require multiple memory accesses.
! By using a larger memory page size, a single TLB entry can represent a
! larger memory range.
! This results in less pressure on a TLB, and memory\-intensive
! applications may have better performance.
! .PP
! However, large pages page memory can negatively affect system
! performance.
! For example, when a large mount of memory is pinned by an application,
! it may create a shortage of regular memory and cause excessive paging in
! other applications and slow down the entire system.
! Also, a system that has been up for a long time could produce excessive
! fragmentation, which could make it impossible to reserve enough large
! page memory.
! When this happens, either the OS or JVM reverts to using regular pages.
! .PP
! Oracle Solaris, Linux, and Windows support large pages.
! .SS Large Pages Support for Oracle Solaris
! .PP
! Oracle Solaris includes Multiple Page Size Support (MPSS).
! No additional configuration is necessary.
! .SS Large Pages Support for Linux
! .PP
! The 2.6 kernel supports large pages.
! Some vendors have backported the code to their 2.4\-based releases.
! To check if your system can support large page memory, try the
! following:
! .IP
! .nf
! \f[CB]
! #\ cat\ /proc/meminfo\ |\ grep\ Huge
! HugePages_Total:\ 0
! HugePages_Free:\ 0
! Hugepagesize:\ 2048\ kB
! \f[R]
! .fi
! .PP
! If the output shows the three "Huge" variables, then your system can
! support large page memory but it needs to be configured.
! If the command prints nothing, then your system doesn\[aq]t support
! large pages.
! To configure the system to use large page memory, login as
! \f[CB]root\f[R], and then follow these steps:
! .IP "1." 3
! If you\[aq]re using the option \f[CB]\-XX:+UseSHM\f[R] (instead of
! \f[CB]\-XX:+UseHugeTLBFS\f[R]), then increase the \f[CB]SHMMAX\f[R] value.
! It must be larger than the Java heap size.
! On a system with 4 GB of physical RAM (or less), the following makes all
! the memory sharable:
! .RS 4
! .RS
! .PP
! \f[CB]#\ echo\ 4294967295\ >\ /proc/sys/kernel/shmmax\f[R]
! .RE
! .RE
! .IP "2." 3
! If you\[aq]re using the option \f[CB]\-XX:+UseSHM\f[R] or
! \f[CB]\-XX:+UseHugeTLBFS\f[R], then specify the number of large pages.
! In the following example, 3 GB of a 4 GB system are reserved for large
! pages (assuming a large page size of 2048kB, then 3 GB = 3 * 1024 MB =
! 3072 MB = 3072 * 1024 kB = 3145728 kB and 3145728 kB / 2048 kB = 1536):
! .RS 4
! .RS
! .PP
! \f[CB]#\ echo\ 1536\ >\ /proc/sys/vm/nr_hugepages\f[R]
! .RE
! .RS
! .PP
! \f[B]Note:\f[R] The values contained in \f[CB]/proc\f[R] resets after you
! reboot your system, so may want to set them in an initialization script
! (for example, \f[CB]rc.local\f[R] or \f[CB]sysctl.conf\f[R]).
  .RE
  .RE
+ .IP \[bu] 2
+ If you configure (or resize) the OS kernel parameters
+ \f[CB]/proc/sys/kernel/shmmax\f[R] or \f[CB]/proc/sys/vm/nr_hugepages\f[R],
+ Java processes may allocate large pages for areas in addition to the
+ Java heap.
+ These steps can allocate large pages for the following areas:
+ .RS 2
+ .IP \[bu] 2
+ Java heap
+ .IP \[bu] 2
+ Code cache
+ .IP \[bu] 2
+ The marking bitmap data structure for the parallel GC
  .PP
! Consequently, if you configure the \f[CB]nr_hugepages\f[R] parameter to
! the size of the Java heap, then the JVM can fail in allocating the code
! cache areas on large pages because these areas are quite large in size.
! .RE
! .SS Large Pages Support for Windows
! .PP
! To use large pages support on Windows, the administrator must first
! assign additional privileges to the user who is running the application:
! .IP "1." 3
! Select \f[B]Control Panel\f[R], \f[B]Administrative Tools\f[R], and then
! \f[B]Local Security Policy\f[R].
! .IP "2." 3
! Select \f[B]Local Policies\f[R] and then \f[B]User Rights Assignment\f[R].
! .IP "3." 3
! Double\-click \f[B]Lock pages in memory\f[R], then add users and/or
! groups.
! .IP "4." 3
! Reboot your system.
! .PP
! Note that these steps are required even if it\[aq]s the administrator
! who\[aq]s running the application, because administrators by default
! don\[aq]t have the privilege to lock pages in memory.
! .SH APPLICATION CLASS DATA SHARING
! .PP
! Application Class Data Sharing (AppCDS) extends class data sharing (CDS)
! to enable application classes to be placed in a shared archive.
! .PP
! In addition to the core library classes, AppCDS supports \f[B]Class Data
! Sharing\f[R]
! [https://docs.oracle.com/en/java/javase/12/vm/class\-data\-sharing.html#GUID\-7EAA3411\-8CF0\-4D19\-BD05\-DF5E1780AA91]
! from the following locations:
! .IP \[bu] 2
! Platform classes from the runtime image
! .IP \[bu] 2
! Application classes from the runtime image
! .IP \[bu] 2
! Application classes from the class path
! .IP \[bu] 2
! Application classes from the module path
! .PP
! Archiving application classes provides better start up time at runtime.
! When running multiple JVM processes, AppCDS also reduces the runtime
! footprint with memory sharing for read\-only metadata.
! .PP
! CDS/AppCDS supports archiving classes from JAR files only.
! .PP
! Prior to JDK 11, a non\-empty directory was reported as a fatal error in
! the following conditions:
! .IP \[bu] 2
! For base CDS, a non\-empty directory cannot exist in the
! \f[CB]\-Xbootclasspath/a\f[R] path
! .IP \[bu] 2
! With \f[CB]\-XX:+UseAppCDS\f[R], a non\-empty directory could not exist in
! the \f[CB]\-Xbootclasspath/a\f[R] path, class path, and module path.
! .PP
! In JDK 11 and later, \f[CB]\-XX:+UseAppCDS\f[R] is obsolete and the
! behavior for a non\-empty directory is based on the class types in the
! classlist.
! A non\-empty directory is reported as a fatal error in the following
! conditions:
! .IP \[bu] 2
! If application classes or platform classes are not loaded, dump time
! only reports an error if a non\-empty directory exists in
! \f[CB]\-Xbootclasspath/a\f[R] path
! .IP \[bu] 2
! If application classes or platform classes are loaded, dump time reports
! an error for a non\-empty directory that exists in
! \f[CB]\-Xbootclasspath/a\f[R] path, class path, or module path
! .PP
! In JDK 11 and later, using
! \f[CB]\-XX:DumpLoadedClassList=\f[R]\f[I]class_list_file\f[R] results a
! generated classlist with all classes (both system library classes and
! application classes) included.
! You no longer have to specify \f[CB]\-XX:+UseAppCDS\f[R] with
! \f[CB]\-XX:DumpLoadedClassList\f[R] to produce a complete class list.
! .PP
! In JDK 11 and later, because \f[CB]UseAppCDS\f[R] is obsolete,
! \f[CB]SharedArchiveFile\f[R] becomes a product flag by default.
! Specifying \f[CB]+UnlockDiagnosticVMOptions\f[R] for
! \f[CB]SharedArchiveFile\f[R] is no longer needed in any configuration.
! .PP
! Class Data Sharing (CDS)/AppCDS does not support archiving array classes
! in a class list.
! When an array in the class list is encountered, CDS dump time gives the
! explicit error message:
! .RS
! .PP
! \f[CB]Preload\ Warning:\ Cannot\ find\f[R] \f[I]array_name\f[R]
! .RE
! .PP
! Although an array in the class list is not allowed, some array classes
! can still be created at CDS/AppCDS dump time.
! Those arrays are created during the execution of the Java code used by
! the Java class loaders (\f[CB]PlatformClassLoader\f[R] and the system
! class loader) to load classes at dump time.
! The created arrays are archived with the rest of the loaded classes.
! .SS Extending Class Data Sharing to Support the Module Path
! .PP
! In JDK 11, Class Data Sharing (CDS) has been improved to support
! archiving classes from the module path.
! .IP \[bu] 2
! To create a CDS archive using the \f[CB]\-\-module\-path\f[R] VM option,
! use the following command line syntax:
! .RS 2
! .RS
! .PP
! \f[CB]java\ \-Xshare:dump\ \-XX:SharedClassListFile=\f[R]\f[I]class_list_file\f[R]
! \f[CB]\-XX:SharedArchiveFile=\f[R]\f[I]shared_archive_file\f[R]
! \f[CB]\-\-module\-path=\f[R]\f[I]path_to_modular_jar\f[R] \f[CB]\-m\f[R]
! \f[I]module_name\f[R]
! .RE
! .RE
! .IP \[bu] 2
! To run with a CDS archive using the \f[CB]\-\-module\-path\f[R] VM option,
! use the following the command line syntax:
! .RS 2
! .RS
! .PP
! \f[CB]java\ \-XX:SharedArchiveFile=\f[R]\f[I]shared_archive_file\f[R]
! \f[CB]\-\-module\-path=\f[R]\f[I]path_to_modular_jar\f[R] \f[CB]\-m\f[R]
! \f[I]module_name\f[R]
  .RE
  .RE
  .PP
! The following table describes how the VM options related to module paths
! can be used along with the \f[CB]\-Xshare\f[R] option.
  .PP
! .TS
! tab(@);
! l l l.
! T{
! Option
! T}@T{
! \-Xshare:dump
! T}@T{
! \-Xshare:{on,auto}
! T}
! _
! T{
! \f[CB]\-\-module\-path\f[R][1] \f[I]mp\f[R]
! T}@T{
! Allowed
! T}@T{
! Allowed[2]
! T}
! T{
! \f[CB]\-\-module\f[R]
! T}@T{
! Allowed
! T}@T{
! Allowed
! T}
! T{
! \f[CB]\-\-add\-module\f[R]
! T}@T{
! Allowed
! T}@T{
! Allowed
! T}
! T{
! \f[CB]\-\-upgrade\-module\-path\f[R][3]
! T}@T{
! Disallowed (exits if specified)
! T}@T{
! Allowed (disables CDS)
! T}
! T{
! \f[CB]\-\-patch\-module\f[R][4]
! T}@T{
! Disallowed (exits if specified)
! T}@T{
! Allowed (disables CDS)
! T}
! T{
! \f[CB]\-\-limit\-modules\f[R][5]
! T}@T{
! Disallowed (exits if specified)
! T}@T{
! Allowed (disables CDS)
! T}
! .TE
  .PP
! [1] Although there are two ways of specifying a module in a
! \f[CB]\-\-module\-path\f[R], that is, modular JAR or exploded module, only
! modular JARs are supported.
  .PP
! [2] Different \f[I]mp\f[R] can be specified during dump time versus run
! time.
! If an archived class K was loaded from \f[CB]mp1.jar\f[R] at dump time,
! but changes in \f[I]mp\f[R] cause it to be available from a different
! \f[CB]mp2.jar\f[R] at run time, then the archived version of K will be
! disregarded at run time; K will be loaded dynamically.
  .PP
! [3] Currently, only two system modules are upgradeable
! (\f[CB]java.compiler\f[R] and \f[CB]jdk.internal.vm.compiler\f[R]).
! However, these modules are seldom upgraded in production software.
  .PP
! [4] As documented in JEP 261, using \f[CB]\-\-patch\-module\f[R] is
! strongly discouraged for production use.
  .PP
! [5] \f[CB]\-\-limit\-modules\f[R] is intended for testing purposes.
! It is seldom used in production software.
  .PP
! If \f[CB]\-\-upgrade\-module\-path\f[R], \f[CB]\-\-patch\-module\f[R], or
! \f[CB]\-\-limit\-modules\f[R] is specified at dump time, an error will be
! printed and the JVM will exit.
! For example, if the \f[CB]\-\-limit\-modules\f[R] option is specified at
! dump time, the user will see the following error:
! .IP
  .nf
! \f[CB]
! Error\ occurred\ during\ initialization\ of\ VM
! Cannot\ use\ the\ following\ option\ when\ dumping\ the\ shared\ archive:\ \-\-limit\-modules
! \f[R]
  .fi
  .PP
! If \f[CB]\-\-upgrade\-module\-path\f[R], \f[CB]\-\-patch\-module\f[R], or
! \f[CB]\-\-limit\-modules\f[R] is specified at run time, a warning message
! will be printed indicating that CDS is disabled.
! For example, if the \f[CB]\-\-limit\-modules\f[R] options is specified at
! run time, the user will see the following warning:
! .IP
  .nf
! \f[CB]
! Java\ HotSpot(TM)\ 64\-Bit\ Server\ VM\ warning:\ CDS\ is\ disabled\ when\ the\ \-\-limit\-modules\ option\ is\ specified.
! \f[R]
  .fi
  .PP
! Several other noteworthy things include:
! .IP \[bu] 2
! Any valid combinations of \f[CB]\-cp\f[R] and \f[CB]\-\-module\-path\f[R]
! are supported.
! .IP \[bu] 2
! A non\-empty directory in the module path causes a fatal error.
! The user will see the following error messages:
! .RS 2
! .IP
  .nf
! \f[CB]
! Error:\ non\-empty\ directory\ <directory>\ Hint:\ enable\ \-Xlog:class+path=info\ to\ diagnose\ the\ failure\ Error\ occurred\ during\ initialization\ of\ VM\ Cannot\ have\ non\-empty\ directory\ in\ paths
! \f[R]
  .fi
  .RE
+ .IP \[bu] 2
+ Unlike the class path, there\[aq]s no restriction that the module path
+ at dump time must be equal to or be a prefix of the module path at run
+ time.
+ .IP \[bu] 2
+ The archive is invalidated if an existing JAR in the module path is
+ updated after archive generation.
+ .IP \[bu] 2
+ Removing a JAR from the module path does not invalidate the shared
+ archive.
+ Archived classes from the removed JAR are not used at runtime.
+ .SS Dynamic CDS archive
  .PP
! Dynamic CDS archive extends AppCDS to allow archiving of classes when a
! Java application exits.
! It improves the usability of AppCDS by eliminating the trial run step
! for creating a class list for each application.
! The archived classes include all loaded application classes and library
! classes that are not present in the default CDS archive which is
! included in the JDK.
  .PP
! A base archive is required when creating a dynamic archive.
! If the base archive is not specified, the default CDS archive is used as
! the base archive.
  .PP
! To create a dynamic CDS archive with the default CDS archive as the base
! archive, just add the
! \f[CB]\-XX:ArchiveClassesAtExit=<dynamic\ archive>\f[R] option to the
! command line for running the Java application.
  .PP
! If the default CDS archive does not exist, the VM will exit with the
! following error:
! .IP
  .nf
! \f[CB]
! ArchiveClassesAtExit\ not\ supported\ when\ base\ CDS\ archive\ is\ not\ loaded
! \f[R]
  .fi
  .PP
! To run the Java application using a dynamic CDS archive, just add the
! \f[CB]\-XX:SharedArchiveFile=<dynamic\ archive>\f[R] option to the command
! line for running the Java application.
  .PP
! The base archive is not required to be specified in the command line.
! The base archive information, including its name and full path, will be
! retrieved from the dynamic archive header.
! Note that the user could also use the \f[CB]\-XX:SharedArchiveFile\f[R]
! option for specifying a regular AppCDS archive.
! Therefore, the specified archive in the \f[CB]\-XX:SharedArchiveFile\f[R]
! option could be either a regular or dynamic archive.
! During VM start up the specified archive header will be read.
! If \f[CB]\-XX:SharedArchiveFile\f[R] refers to a regular archive, then the
! behavior will be unchanged.
! If \f[CB]\-XX:SharedArchiveFile\f[R] refers to a dynamic archive, the VM
! will retrieve the base archive location from the dynamic archive.
! If the dynamic archive was created with the default CDS archive, then
! the current default CDS archive will be used, and will be found relative
! to the current run time environment.
  .PP
! Please refer to \f[B]JDK\-8221706\f[R]
! [https://bugs.openjdk.java.net/browse/JDK\-8221706] for details on error
! checking during dynamic CDS archive dump time and run time.
! .SS Creating a Shared Archive File and Using It to Run an Application
! .SS AppCDS archive
  .PP
! The following steps create a shared archive file that contains all the
! classes used by the \f[CB]test.Hello\f[R] application.
! The last step runs the application with the shared archive file.
! .IP "1." 3
! Create a list of all classes used by the \f[CB]test.Hello\f[R]
! application.
! The following command creates a file named \f[CB]hello.classlist\f[R] that
! contains a list of all classes used by this application:
  .RS 4
! .RS
  .PP
! \f[CB]java\ \-Xshare:off\ \-XX:DumpLoadedClassList=hello.classlist\ \-cp\ hello.jar\ test.Hello\f[R]
  .RE
  .PP
! Note that the classpath specified by the \f[CB]\-cp\f[R] parameter must
! contain only JAR files.
  .RE
! .IP "2." 3
! Create a shared archive, named \f[CB]hello.jsa\f[R], that contains all the
! classes in \f[CB]hello.classlist\f[R]:
  .RS 4
! .RS
  .PP
! \f[CB]java\ \-Xshare:dump\ \-XX:SharedArchiveFile=hello.jsa\ \-XX:SharedClassListFile=hello.classlist\ \-cp\ hello.jar\f[R]
  .RE
  .PP
! Note that the classpath used at archive creation time must be the same
! as (or a prefix of) the classpath used at run time.
  .RE
! .IP "3." 3
! Run the application \f[CB]test.Hello\f[R] with the shared archive
! \f[CB]hello.jsa\f[R]:
  .RS 4
! .RS
  .PP
! \f[CB]java\ \-XX:SharedArchiveFile=hello.jsa\ \-cp\ hello.jar\ test.Hello\f[R]
  .RE
  .RE
! .IP "4." 3
! \f[B]Optional\f[R] Verify that the \f[CB]test.Hello\f[R] application is
! using the class contained in the \f[CB]hello.jsa\f[R] shared archive:
  .RS 4
! .RS
! .PP
! \f[CB]java\ \-XX:SharedArchiveFile=hello.jsa\ \-cp\ hello.jar\ \-verbose:class\ test.Hello\f[R]
  .RE
  .PP
! The output of this command should contain the following text:
! .IP
  .nf
! \f[CB]
! Loaded\ test.Hello\ from\ shared\ objects\ file\ by\ sun/misc/Launcher$AppClassLoader
! \f[R]
  .fi
  .RE
+ .SS Dynamic CDS archive
  .PP
! The following steps create a dynamic CDS archive file that contains the
! classes used by the \f[CB]test.Hello\f[R] application and are not included
! in the default CDS archive.
! The second step runs the application with the dynamic CDS archive.
! .IP "1." 3
! Create a dynamic CDS archive, named \f[CB]hello.jsa\f[R], that contains
! all the classes in \f[CB]hello.jar\f[R] loaded by the application
! \f[CB]test.Hello\f[R]:
  .RS 4
! .RS
  .PP
! \f[CB]java\ \-XX:ArchiveClassesAtExit=hello.jsa\ \-cp\ hello.jar\ Hello\f[R]
  .RE
  .PP
! Note that the classpath used at archive creation time must be the same
! as (or a prefix of) the classpath used at run time.
  .RE
! .IP "2." 3
! Run the application \f[CB]test.Hello\f[R] with the shared archive
! \f[CB]hello.jsa\f[R]:
  .RS 4
! .RS
  .PP
! \f[CB]java\ \-XX:SharedArchiveFile=hello.jsa\ \-cp\ hello.jar\ test.Hello\f[R]
  .RE
  .RE
+ .IP "3." 3
+ \f[B]Optional\f[R] Repeat step 4 of the previous section to verify that
+ the \f[CB]test.Hello\f[R] application is using the class contained in the
+ \f[CB]hello.jsa\f[R] shared archive.
  .PP
! To automate the above steps 1 and 2, one can write a script such as the
! following:
! .IP
  .nf
! \f[CB]
! \ \ \ \ ARCHIVE=hello.jsa
! \ \ \ \ if\ test\ \-f\ $ARCHIVE;\ then
! \ \ \ \ \ \ \ \ FLAG="\-XX:SharedArchiveFile=$ARCHIVE"
! \ \ \ \ else
! \ \ \ \ \ \ \ \ FLAG="\-XX:ArchiveClassesAtExit=$ARCHIVE"
! \ \ \ \ fi
! \ \ \ \ $JAVA_HOME/bin/java\ \-cp\ hello.jar\ $FLAG\ test.Hello
! \f[R]
  .fi
  .PP
! Like an AppCDS archive, the archive needs to be re\-generated if the
! Java version has changed.
! The above script could be adjusted to account for the Java version as
! follows:
! .IP
  .nf
! \f[CB]
! \ \ \ \ ARCHIVE=hello.jsa
! \ \ \ \ VERSION=foo.version
! \ \ \ \ if\ test\ \-f\ $ARCHIVE\ \-a\ \-f\ $VERSION\ &&\ cmp\ \-s\ $VERSION\ $JAVA_HOME/release;\ then
! \ \ \ \ \ \ \ \ FLAG="\-XX:SharedArchiveFile=$ARCHIVE"
! \ \ \ \ else
! \ \ \ \ \ \ \ \ FLAG="\-XX:ArchiveClassesAtExit=$ARCHIVE"
! \ \ \ \ \ \ \ \ cp\ \-f\ $JAVA_HOME/release\ $VERSION
! \ \ \ \ fi
! \ \ \ \ $JAVA_HOME/bin/java\ \-cp\ hello.jar\ $FLAG\ test.Hello
! \f[R]
  .fi
  .PP
! Currently, we don\[aq]t support concurrent dumping operations to the
! same CDS archive.
! Care should be taken to avoid multiple writers to the same CDS archive.
  .PP
! The user could also create a dynamic CDS archive with a specific base
! archive, e.g.
! named as \f[CB]base.jsa\f[R] as follows:
! .RS
  .PP
! \f[CB]java\ \-XX:SharedArchiveFile=base.jsa\ \-XX:ArchiveClassesAtExit=hello.jsa\ \-cp\ hello.jar\ Hello\f[R]
  .RE
  .PP
! To run the application using the dynamic CDS archive \f[CB]hello.jsa\f[R]
! and a specific base CDS archive \f[CB]base.jsa\f[R]:
! .RS
  .PP
! \f[CB]java\ \-XX:SharedArchiveFile=base.jsa:hello.jsa\ \-cp\ hello.jar\ Hello\f[R]
  .RE
  .PP
! Note that on Windows, the above path delimiter \f[CB]:\f[R] should be
! replaced with \f[CB];\f[R].
  .PP
! The above command for specifying a base archive is useful if the base
! archive used for creating the dynamic archive has been moved.
! Normally, just specifying the dynamic archive should be sufficient since
! the base archive info can be retrieved from the dynamic archive header.
! .SS Sharing a Shared Archive Across Multiple Application Processes
  .PP
! You can share the same archive file across multiple applications
! processes.
! This reduces memory usage because the archive is memory\-mapped into the
! address space of the processes.
! The operating system automatically shares the read\-only pages across
! these processes.
  .PP
! The following steps demonstrate how to create a common archive that can
! be shared by different applications.
! Classes from \f[CB]common.jar\f[R], \f[CB]hello.jar\f[R] and \f[CB]hi.jar\f[R]
! are archived in the \f[CB]common.jsa\f[R] because they are all in the
! classpath during the archiving step (step 3).
  .PP
! To include classes from \f[CB]hello.jar\f[R] and \f[CB]hi.jar\f[R], the
! \f[CB]\&.jar\f[R] files must be added to the classpath specified by the
! \f[CB]\-cp\f[R] parameter.
! .IP "1." 3
! Create a list of all classes used by the \f[CB]Hello\f[R] application and
! another list for the \f[CB]Hi\f[R] application:
  .RS 4
! .RS
  .PP
! \f[CB]java\ \-XX:DumpLoadedClassList=hello.classlist\ \-cp\ common.jar:hello.jar\ Hello\f[R]
  .RE
+ .RS
  .PP
! \f[CB]java\ \-XX:DumpLoadedClassList=hi.classlist\ \-cp\ common.jar:hi.jar\ Hi\f[R]
  .RE
  .RE
! .IP "2." 3
! Create a single list of classes used by all the applications that will
! share the shared archive file.
  .RS 4
  .PP
! \f[B]Oracle Solaris, Linux, and macOS\f[R] The following commands combine
! the files \f[CB]hello.classlist\f[R] and \f[CB]hi.classlist\f[R] into one
! file, \f[CB]common.classlist\f[R]:
! .RS
  .PP
! \f[CB]cat\ hello.classlist\ hi.classlist\ >\ common.classlist\f[R]
  .RE
  .PP
! \f[B]Windows\f[R] The following commands combine the files
! \f[CB]hello.classlist\f[R] and \f[CB]hi.classlist\f[R] into one file,
! \f[CB]common.classlist\f[R]:
! .RS
  .PP
! \f[CB]type\ hello.classlist\ hi.classlist\ >\ common.classlist\f[R]
  .RE
  .RE
! .IP "3." 3
! Create a shared archive named \f[CB]common.jsa\f[R] that contains all the
! classes in \f[CB]common.classlist\f[R]:
  .RS 4
! .RS
  .PP
! \f[CB]java\ \-Xshare:dump\ \-XX:SharedArchiveFile=common.jsa\ \-XX:SharedClassListFile=common.classlist\ \-cp\ common.jar:hello.jar:hi.jar\f[R]
  .RE
  .PP
! The classpath parameter used is the common class path prefix shared by
! the \f[CB]Hello\f[R] and \f[CB]Hi\f[R] applications.
  .RE
! .IP "4." 3
! Run the \f[CB]Hello\f[R] and \f[CB]Hi\f[R] applications with the same shared
! archive:
  .RS 4
! .RS
  .PP
! \f[CB]java\ \-XX:SharedArchiveFile=common.jsa\ \-cp\ common.jar:hello.jar:hi.jar\ Hello\f[R]
  .RE
+ .RS
  .PP
! \f[CB]java\ \-XX:SharedArchiveFile=common.jsa\ \-cp\ common.jar:hello.jar:hi.jar\ Hi\f[R]
  .RE
  .RE
+ .SS Specifying Additional Shared Data Added to an Archive File
  .PP
! The \f[CB]SharedArchiveConfigFile\f[R] option is used to specify
! additional shared data to add to the archive file.
! .RS
  .PP
! \f[CB]\-XX:SharedArchiveConfigFile=\f[R]\f[I]shared_config_file\f[R]
  .RE
  .PP
! JDK 9 and later supports adding both symbols and\ string objects to an
! archive for memory sharing\ when you have multiple JVM processes running
! on the same host.
! An example of this is having multiple JVM processes that use the same
! set of Java EE classes.
! When these common classes are loaded and used, new symbols and strings
! may be created and added to the JVM\[aq]s internal "symbol" and "string"
! tables.\ At runtime, the symbols or string objects mapped from the
! archive file can be shared across multiple JVM processes, resulting in a
! reduction of overall memory usage.\ In addition, archiving strings also
! provides added performance benefits in both startup time and runtime
! execution.
  .PP
! In JDK 10 and later, CONSTANT_String entries in archived classes are
! resolved to interned String objects at dump time, and all interned
! String objects are archived.
! However, even though all CONSTANT_String literals in all archived
! classes are resolved, it might still beneficial to add additional
! strings that are not string literals in class files, but are likely to
! be used by your application at run time.
  .PP
! Symbol data should be generated by the \f[CB]jcmd\f[R] tool attaching to a
! running JVM process.
! See \f[B]jcmd\f[R].
  .PP
! The following is an example of the symbol dumping command in
! \f[CB]jcmd\f[R]:\ 
! .RS
  .PP
! \f[CB]jcmd\f[R] \f[I]pid\f[R] \f[CB]VM.symboltable\ \-verbose\f[R]
  .RE
+ .RS
  .PP
! \f[B]Note:\f[R] The first line (process ID) and the second line
! (\f[CB]\@VERSION\ ...\f[R]) of this \f[CB]jcmd\f[R] output should be
! excluded from the configuration file.
  .RE
+ .SS Example of a Configuration File
  .PP
! The following is an example of a configuration file:
! .IP
! .nf
! \f[CB]
! VERSION:\ 1.0
! \@SECTION:\ Symbol
! 10\ \-1:\ linkMethod
! \f[R]
! .fi
  .PP
! In the configuration file example, the \f[CB]\@SECTION:\ Symbol\f[R] entry
! uses the following format:
! .RS
  .PP
! \f[I]length\f[R] \f[I]refcount\f[R]\f[CB]:\f[R] \f[I]symbol\f[R]
  .RE
  .PP
! The \f[I]refcount\f[R] for a shared symbol is always \f[CB]\-1\f[R].
  .PP
! \f[CB]\@SECTION\f[R] specifies the type of the section that follows it.
! All data within the section must be the same type that\[aq]s specified
! by \f[CB]\@SECTION\f[R].
! Different types of data can\[aq]t be mixed.
! Multiple separated data sections for the same type specified by
! different \f[CB]\@SECTION\f[R] are allowed within one
! \f[CB]shared_config_file\f[R] .
! .SH PERFORMANCE TUNING EXAMPLES
  .PP
! You can use the Java advanced runtime options to optimize the
! performance of your applications.
! .SS Tuning for Higher Throughput
  .PP
! Use the following commands and advanced options to achieve higher
! throughput performance for your application:
! .RS
  .PP
! \f[CB]java\ \-server\ \-XX:+UseParallelGC\ \-XX:+UseLargePages\ \-Xmn10g\ \ \-Xms26g\ \-Xmx26g\f[R]
  .RE
! .SS Tuning for Lower Response Time
  .PP
! Use the following commands and advanced options to achieve lower
! response times for your application:
! .RS
  .PP
! \f[CB]java\ \-XX:+UseG1GC\ \-Xms26g\ Xmx26g\ \-XX:MaxGCPauseMillis=500\f[R]
  .RE
! .SS Keeping the Java Heap Small and Reducing the Dynamic Footprint of
! Embedded Applications
  .PP
! Use the following advanced runtime options to keep the Java heap small
! and reduce the dynamic footprint of embedded applications:
! .RS
  .PP
! \f[CB]\-XX:MaxHeapFreeRatio=10\ \-XX:MinHeapFreeRatio=5\f[R]
  .RE
! .RS
  .PP
! \f[B]Note:\f[R] The defaults for these two options are 70% and 40%
! respectively.
! Because performance sacrifices can occur when using these small
! settings, you should optimize for a small footprint by reducing these
! settings as much as possible without introducing unacceptable
! performance degradation.
  .RE
! .SH EXIT STATUS
  .PP
! The following exit values are typically returned by the launcher when
! the launcher is called with the wrong arguments, serious errors, or
! exceptions thrown by the JVM.
! However, a Java application may choose to return any value by using the
! API call \f[CB]System.exit(exitValue)\f[R].
! The values are:
! .IP \[bu] 2
! \f[CB]0\f[R]: Successful completion
! .IP \[bu] 2
! \f[CB]>0\f[R]: An error occurred