* To automatically track startup performance in an app or applet,
* use the command-line parameter sun.perflog as follows:
*
}" will cause
* that given filename to be created and used for all output.
*
* By default, times are measured using System.currentTimeMillis(). To use
* System.nanoTime() instead, add the command-line parameter:
-Dsun.perflog.nano=true
*
*
* Warning: Use at your own risk!
* This class is intended for internal testing
* purposes only and may be removed at any time. More
* permanent monitoring and profiling APIs are expected to be
* developed for future releases and this class will cease to
* exist once those APIs are in place.
* @author Chet Haase
*/
public class PerformanceLogger {
// Timing values of global interest
private static final int START_INDEX = 0; // VM start
private static final int LAST_RESERVED = START_INDEX;
private static boolean perfLoggingOn = false;
private static boolean useNanoTime = false;
private static Vector times;
private static String logFileName = null;
private static Writer logWriter = null;
private static long baseTime;
static {
String perfLoggingProp =
java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction("sun.perflog"));
if (perfLoggingProp != null) {
perfLoggingOn = true;
// Check if we should use nanoTime
String perfNanoProp =
java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction("sun.perflog.nano"));
if (perfNanoProp != null) {
useNanoTime = true;
}
// Now, figure out what the user wants to do with the data
if (perfLoggingProp.regionMatches(true, 0, "file:", 0, 5)) {
logFileName = perfLoggingProp.substring(5);
}
if (logFileName != null) {
if (logWriter == null) {
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction() {
public Void run() {
try {
File logFile = new File(logFileName);
logFile.createNewFile();
logWriter = new FileWriter(logFile);
} catch (Exception e) {
System.out.println(e + ": Creating logfile " +
logFileName +
". Log to console");
}
return null;
}
});
}
}
if (logWriter == null) {
logWriter = new OutputStreamWriter(System.out);
}
}
times = new Vector(10);
// Reserve predefined slots
for (int i = 0; i <= LAST_RESERVED; ++i) {
times.add(new TimeData("Time " + i + " not set", 0));
}
}
/**
* Returns status of whether logging is enabled or not. This is
* provided as a convenience method so that users do not have to
* perform the same GetPropertyAction check as above to determine whether
* to enable performance logging.
*/
public static boolean loggingEnabled() {
return perfLoggingOn;
}
/**
* Internal class used to store time/message data together.
*/
static class TimeData {
String message;
long time;
TimeData(String message, long time) {
this.message = message;
this.time = time;
}
String getMessage() {
return message;
}
long getTime() {
return time;
}
}
/**
* Return the current time, in millis or nanos as appropriate
*/
private static long getCurrentTime() {
if (useNanoTime) {
return System.nanoTime();
} else {
return System.currentTimeMillis();
}
}
/**
* Sets the start time. Ideally, this is the earliest time available
* during the startup of a Java applet or application. This time is
* later used to analyze the difference between the initial startup
* time and other events in the system (such as an applet's init time).
*/
public static void setStartTime(String message) {
if (loggingEnabled()) {
long nowTime = getCurrentTime();
setStartTime(message, nowTime);
}
}
/**
* Sets the base time, output can then
* be displayed as offsets from the base time;.
*/
public static void setBaseTime(long time) {
if (loggingEnabled()) {
baseTime = time;
}
}
/**
* Sets the start time.
* This version of the method is
* given the time to log, instead of expecting this method to
* get the time itself. This is done in case the time was
* recorded much earlier than this method was called.
*/
public static void setStartTime(String message, long time) {
if (loggingEnabled()) {
times.set(START_INDEX, new TimeData(message, time));
}
}
/**
* Gets the start time, which should be the time when
* the java process started, prior to the VM actually being
* loaded.
*/
public static long getStartTime() {
if (loggingEnabled()) {
return times.get(START_INDEX).getTime();
} else {
return 0;
}
}
/**
* Sets the value of a given time and returns the index of the
* slot that that time was stored in.
*/
public static int setTime(String message) {
if (loggingEnabled()) {
long nowTime = getCurrentTime();
return setTime(message, nowTime);
} else {
return 0;
}
}
/**
* Sets the value of a given time and returns the index of the
* slot that that time was stored in.
* This version of the method is
* given the time to log, instead of expecting this method to
* get the time itself. This is done in case the time was
* recorded much earlier than this method was called.
*/
public static int setTime(String message, long time) {
if (loggingEnabled()) {
// times is already synchronized, but we need to ensure that
// the size used in times.set() is the same used when returning
// the index of that operation.
synchronized (times) {
times.add(new TimeData(message, time));
return (times.size() - 1);
}
} else {
return 0;
}
}
/**
* Returns time at given index.
*/
public static long getTimeAtIndex(int index) {
if (loggingEnabled()) {
return times.get(index).getTime();
} else {
return 0;
}
}
/**
* Returns message at given index.
*/
public static String getMessageAtIndex(int index) {
if (loggingEnabled()) {
return times.get(index).getMessage();
} else {
return null;
}
}
/**
* Outputs all data to parameter-specified Writer object
*/
public static void outputLog(Writer writer) {
if (loggingEnabled()) {
try {
synchronized(times) {
for (int i = 0; i < times.size(); ++i) {
TimeData td = times.get(i);
if (td != null) {
writer.write(i + " " + td.getMessage() + ": " +
(td.getTime() - baseTime) + "\n");
}
}
}
writer.flush();
} catch (Exception e) {
System.out.println(e + ": Writing performance log to " +
writer);
}
}
}
/**
* Outputs all data to whatever location the user specified
* via sun.perflog command-line parameter.
*/
public static void outputLog() {
outputLog(logWriter);
}
}