1 /* 2 * Copyright (c) 2002, 2006, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package sun.misc; 26 27 import java.nio.ByteBuffer; 28 import java.security.Permission; 29 import java.security.PrivilegedAction; 30 import java.io.IOException; 31 import java.io.UnsupportedEncodingException; 32 33 /** 34 * The Perf class provides the ability to attach to an instrumentation 35 * buffer maintained by a Java virtual machine. The instrumentation 36 * buffer may be for the Java virtual machine running the methods of 37 * this class or it may be for another Java virtual machine on the 38 * same system. 39 * <p> 40 * In addition, this class provides methods to create instrumentation 41 * objects in the instrumentation buffer for the Java virtual machine 42 * that is running these methods. It also contains methods for acquiring 43 * the value of a platform specific high resolution clock for time 44 * stamp and interval measurement purposes. 45 * 46 * @author Brian Doherty 47 * @since 1.4.2 48 * @see #getPerf 49 * @see sun.misc.Perf$GetPerfAction 50 * @see java.nio.ByteBuffer 51 */ 52 public final class Perf { 53 54 private static Perf instance; 55 56 private static final int PERF_MODE_RO = 0; 57 private static final int PERF_MODE_RW = 1; 58 59 private Perf() { } // prevent instantiation 60 61 /** 62 * The GetPerfAction class is a convenience class for acquiring access 63 * to the singleton Perf instance using the 64 * <code>AccessController.doPrivileged()</code> method. 65 * <p> 66 * An instance of this class can be used as the argument to 67 * <code>AccessController.doPrivileged(PrivilegedAction)</code>. 68 * <p> Here is a suggested idiom for use of this class: 69 * 70 * <blockquote><pre> 71 * class MyTrustedClass { 72 * private static final Perf perf = 73 * AccessController.doPrivileged(new Perf.GetPerfAction<Perf>()); 74 * ... 75 * } 76 * </pre></blockquote> 77 * <p> 78 * In the presence of a security manager, the <code>MyTrustedClass</code> 79 * class in the above example will need to be granted the 80 * <em>"sun.misc.Perf.getPerf"</em> <code>RuntimePermission</code> 81 * permission in order to successfully acquire the singleton Perf instance. 82 * <p> 83 * Please note that the <em>"sun.misc.Perf.getPerf"</em> permission 84 * is not a JDK specified permission. 85 * 86 * @see java.security.AccessController#doPrivileged(PrivilegedAction) 87 * @see java.lang.RuntimePermission 88 */ 89 public static class GetPerfAction implements PrivilegedAction<Perf> 90 { 91 /** 92 * Run the <code>Perf.getPerf()</code> method in a privileged context. 93 * 94 * @see #getPerf 95 */ 96 public Perf run() { 97 return getPerf(); 98 } 99 } 100 101 /** 102 * Return a reference to the singleton Perf instance. 103 * <p> 104 * The getPerf() method returns the singleton instance of the Perf 105 * class. The returned object provides the caller with the capability 106 * for accessing the instrumentation buffer for this or another local 107 * Java virtual machine. 108 * <p> 109 * If a security manager is installed, its <code>checkPermission</code> 110 * method is called with a <code>RuntimePermission</code> with a target 111 * of <em>"sun.misc.Perf.getPerf"</em>. A security exception will result 112 * if the caller has not been granted this permission. 113 * <p> 114 * Access to the returned <code>Perf</code> object should be protected 115 * by its caller and not passed on to untrusted code. This object can 116 * be used to attach to the instrumentation buffer provided by this Java 117 * virtual machine or for those of other Java virtual machines running 118 * on the same system. The instrumentation buffer may contain senstitive 119 * information. API's built on top of this interface may want to provide 120 * finer grained access control to the contents of individual 121 * instrumentation objects contained within the buffer. 122 * <p> 123 * Please note that the <em>"sun.misc.Perf.getPerf"</em> permission 124 * is not a JDK specified permission. 125 * 126 * @return A reference to the singleton Perf instance. 127 * @throws AccessControlException if a security manager exists and 128 * its <code>checkPermission</code> method doesn't allow 129 * access to the <em>"sun.misc.Perf.getPerf"</em> target. 130 * @see java.lang.RuntimePermission 131 * @see #attach 132 */ 133 public static Perf getPerf() 134 { 135 SecurityManager security = System.getSecurityManager(); 136 if (security != null) { 137 Permission perm = new RuntimePermission("sun.misc.Perf.getPerf"); 138 security.checkPermission(perm); 139 } 140 141 return instance; 142 } 143 144 /** 145 * Attach to the instrumentation buffer for the specified Java virtual 146 * machine. 147 * <p> 148 * This method will attach to the instrumentation buffer for the 149 * specified virtual machine. It returns a <code>ByteBuffer</code> object 150 * that is initialized to access the instrumentation buffer for the 151 * indicated Java virtual machine. The <code>lvmid</code> parameter is 152 * a integer value that uniquely identifies the target local Java virtual 153 * machine. It is typically, but not necessarily, the process id of 154 * the target Java virtual machine. 155 * <p> 156 * If the <code>lvmid</code> identifies a Java virtual machine different 157 * from the one running this method, then the coherency characteristics 158 * of the buffer are implementation dependent. Implementations that do 159 * not support named, coherent, shared memory may return a 160 * <code>ByteBuffer</code> object that contains only a snap shot of the 161 * data in the instrumentation buffer. Implementations that support named, 162 * coherent, shared memory, may return a <code>ByteBuffer</code> object 163 * that will be changing dynamically over time as the target Java virtual 164 * machine updates its mapping of this buffer. 165 * <p> 166 * If the <code>lvmid</code> is 0 or equal to the actual <code>lvmid</code> 167 * for the Java virtual machine running this method, then the returned 168 * <code>ByteBuffer</code> object will always be coherent and dynamically 169 * changing. 170 * <p> 171 * The attach mode specifies the access permissions requested for the 172 * instrumentation buffer of the target virtual machine. The permitted 173 * access permissions are: 174 * <p> 175 * <bl> 176 * <li>"r" - Read only access. This Java virtual machine has only 177 * read access to the instrumentation buffer for the target Java 178 * virtual machine. 179 * <li>"rw" - Read/Write access. This Java virtual machine has read and 180 * write access to the instrumentation buffer for the target Java virtual 181 * machine. This mode is currently not supported and is reserved for 182 * future enhancements. 183 * </bl> 184 * 185 * @param lvmid an integer that uniquely identifies the 186 * target local Java virtual machine. 187 * @param mode a string indicating the attach mode. 188 * @return ByteBuffer a direct allocated byte buffer 189 * @throws IllegalArgumentException The lvmid or mode was invalid. 190 * @throws IOException An I/O error occurred while trying to acquire 191 * the instrumentation buffer. 192 * @throws OutOfMemoryError The instrumentation buffer could not be mapped 193 * into the virtual machine's address space. 194 * @see java.nio.ByteBuffer 195 */ 196 public ByteBuffer attach(int lvmid, String mode) 197 throws IllegalArgumentException, IOException 198 { 199 if (mode.compareTo("r") == 0) { 200 return attachImpl(null, lvmid, PERF_MODE_RO); 201 } 202 else if (mode.compareTo("rw") == 0) { 203 return attachImpl(null, lvmid, PERF_MODE_RW); 204 } 205 else { 206 throw new IllegalArgumentException("unknown mode"); 207 } 208 } 209 210 /** 211 * Attach to the instrumentation buffer for the specified Java virtual 212 * machine owned by the given user. 213 * <p> 214 * This method behaves just as the <code>attach(int lvmid, String mode) 215 * </code> method, except that it only searches for Java virtual machines 216 * owned by the specified user. 217 * 218 * @param user A <code>String</code> object containing the 219 * name of the user that owns the target Java 220 * virtual machine. 221 * @param lvmid an integer that uniquely identifies the 222 * target local Java virtual machine. 223 * @param mode a string indicating the attach mode. 224 * @return ByteBuffer a direct allocated byte buffer 225 * @throws IllegalArgumentException The lvmid or mode was invalid. 226 * @throws IOException An I/O error occurred while trying to acquire 227 * the instrumentation buffer. 228 * @throws OutOfMemoryError The instrumentation buffer could not be mapped 229 * into the virtual machine's address space. 230 * @see java.nio.ByteBuffer 231 */ 232 public ByteBuffer attach(String user, int lvmid, String mode) 233 throws IllegalArgumentException, IOException 234 { 235 if (mode.compareTo("r") == 0) { 236 return attachImpl(user, lvmid, PERF_MODE_RO); 237 } 238 else if (mode.compareTo("rw") == 0) { 239 return attachImpl(user, lvmid, PERF_MODE_RW); 240 } 241 else { 242 throw new IllegalArgumentException("unknown mode"); 243 } 244 } 245 246 /** 247 * Call the implementation specific attach method. 248 * <p> 249 * This method calls into the Java virtual machine to perform the platform 250 * specific attach method. Buffers returned from this method are 251 * internally managed as <code>PhantomRefereces</code> to provide for 252 * guaranteed, secure release of the native resources. 253 * 254 * @param user A <code>String</code> object containing the 255 * name of the user that owns the target Java 256 * virtual machine. 257 * @param lvmid an integer that uniquely identifies the 258 * target local Java virtual machine. 259 * @param mode a string indicating the attach mode. 260 * @return ByteBuffer a direct allocated byte buffer 261 * @throws IllegalArgumentException The lvmid or mode was invalid. 262 * @throws IOException An I/O error occurred while trying to acquire 263 * the instrumentation buffer. 264 * @throws OutOfMemoryError The instrumentation buffer could not be mapped 265 * into the virtual machine's address space. 266 */ 267 private ByteBuffer attachImpl(String user, int lvmid, int mode) 268 throws IllegalArgumentException, IOException 269 { 270 final ByteBuffer b = attach(user, lvmid, mode); 271 272 if (lvmid == 0) { 273 // The native instrumentation buffer for this Java virtual 274 // machine is never unmapped. 275 return b; 276 } 277 else { 278 // This is an instrumentation buffer for another Java virtual 279 // machine with native resources that need to be managed. We 280 // create a duplicate of the native ByteBuffer and manage it 281 // with a Cleaner object (PhantomReference). When the duplicate 282 // becomes only phantomly reachable, the native resources will 283 // be released. 284 285 final ByteBuffer dup = b.duplicate(); 286 Cleaner.create(dup, new Runnable() { 287 public void run() { 288 try { 289 instance.detach(b); 290 } 291 catch (Throwable th) { 292 // avoid crashing the reference handler thread, 293 // but provide for some diagnosability 294 assert false : th.toString(); 295 } 296 } 297 }); 298 return dup; 299 } 300 } 301 302 /** 303 * Native method to perform the implementation specific attach mechanism. 304 * <p> 305 * The implementation of this method may return distinct or identical 306 * <code>ByteBuffer</code> objects for two distinct calls requesting 307 * attachment to the same Java virtual machine. 308 * <p> 309 * For the Sun HotSpot JVM, two distinct calls to attach to the same 310 * target Java virtual machine will result in two distinct ByteBuffer 311 * objects returned by this method. This may change in a future release. 312 * 313 * @param user A <code>String</code> object containing the 314 * name of the user that owns the target Java 315 * virtual machine. 316 * @param lvmid an integer that uniquely identifies the 317 * target local Java virtual machine. 318 * @param mode a string indicating the attach mode. 319 * @return ByteBuffer a direct allocated byte buffer 320 * @throws IllegalArgumentException The lvmid or mode was invalid. 321 * @throws IOException An I/O error occurred while trying to acquire 322 * the instrumentation buffer. 323 * @throws OutOfMemoryError The instrumentation buffer could not be mapped 324 * into the virtual machine's address space. 325 */ 326 private native ByteBuffer attach(String user, int lvmid, int mode) 327 throws IllegalArgumentException, IOException; 328 329 /** 330 * Native method to perform the implementation specific detach mechanism. 331 * <p> 332 * If this method is passed a <code>ByteBuffer</code> object that is 333 * not created by the <code>attach</code> method, then the results of 334 * this method are undefined, with unpredictable and potentially damaging 335 * effects to the Java virtual machine. To prevent accidental or malicious 336 * use of this method, all native ByteBuffer created by the <code> 337 * attach</code> method are managed internally as PhantomReferences 338 * and resources are freed by the system. 339 * <p> 340 * If this method is passed a <code>ByteBuffer</code> object created 341 * by the <code>attach</code> method with a lvmid for the Java virtual 342 * machine running this method (lvmid=0, for example), then the detach 343 * request is silently ignored. 344 * 345 * @param ByteBuffer A direct allocated byte buffer created by the 346 * <code>attach</code> method. 347 * @see java.nio.ByteBuffer 348 * @see #attach 349 */ 350 private native void detach(ByteBuffer bb); 351 352 /** 353 * Create a <code>long</code> scalar entry in the instrumentation buffer 354 * with the given variability characteristic, units, and initial value. 355 * <p> 356 * Access to the instrument is provided through the returned <code> 357 * ByteBuffer</code> object. Typically, this object should be wrapped 358 * with <code>LongBuffer</code> view object. 359 * 360 * @param variability the variability characteristic for this entry. 361 * @param units the units for this entry. 362 * @param name the name of this entry. 363 * @param value the initial value for this entry. 364 * @return ByteBuffer a direct allocated ByteBuffer object that 365 * allows write access to a native memory location 366 * containing a <code>long</code> value. 367 * 368 * see sun.misc.perf.Variability 369 * see sun.misc.perf.Units 370 * @see java.nio.ByteBuffer 371 */ 372 public native ByteBuffer createLong(String name, int variability, 373 int units, long value); 374 375 /** 376 * Create a <code>String</code> entry in the instrumentation buffer with 377 * the given variability characteristic, units, and initial value. 378 * <p> 379 * The maximum length of the <code>String</code> stored in this string 380 * instrument is given in by <code>maxLength</code> parameter. Updates 381 * to this instrument with <code>String</code> values with lengths greater 382 * than <code>maxLength</code> will be truncated to <code>maxLength</code>. 383 * The truncated value will be terminated by a null character. 384 * <p> 385 * The underlying implementation may further limit the length of the 386 * value, but will continue to preserve the null terminator. 387 * <p> 388 * Access to the instrument is provided through the returned <code> 389 * ByteBuffer</code> object. 390 * 391 * @param variability the variability characteristic for this entry. 392 * @param units the units for this entry. 393 * @param name the name of this entry. 394 * @param value the initial value for this entry. 395 * @param maxLength the maximum string length for this string 396 * instrument. 397 * @return ByteBuffer a direct allocated ByteBuffer that allows 398 * write access to a native memory location 399 * containing a <code>long</code> value. 400 * 401 * see sun.misc.perf.Variability 402 * see sun.misc.perf.Units 403 * @see java.nio.ByteBuffer 404 */ 405 public ByteBuffer createString(String name, int variability, 406 int units, String value, int maxLength) 407 { 408 byte[] v = getBytes(value); 409 byte[] v1 = new byte[v.length+1]; 410 System.arraycopy(v, 0, v1, 0, v.length); 411 v1[v.length] = '\0'; 412 return createByteArray(name, variability, units, v1, Math.max(v1.length, maxLength)); 413 } 414 415 /** 416 * Create a <code>String</code> entry in the instrumentation buffer with 417 * the given variability characteristic, units, and initial value. 418 * <p> 419 * The maximum length of the <code>String</code> stored in this string 420 * instrument is implied by the length of the <code>value</code> parameter. 421 * Subsequent updates to the value of this instrument will be truncated 422 * to this implied maximum length. The truncated value will be terminated 423 * by a null character. 424 * <p> 425 * The underlying implementation may further limit the length of the 426 * initial or subsequent value, but will continue to preserve the null 427 * terminator. 428 * <p> 429 * Access to the instrument is provided through the returned <code> 430 * ByteBuffer</code> object. 431 * 432 * @param variability the variability characteristic for this entry. 433 * @param units the units for this entry. 434 * @param name the name of this entry. 435 * @param value the initial value for this entry. 436 * @return ByteBuffer a direct allocated ByteBuffer that allows 437 * write access to a native memory location 438 * containing a <code>long</code> value. 439 * 440 * see sun.misc.perf.Variability 441 * see sun.misc.perf.Units 442 * @see java.nio.ByteBuffer 443 */ 444 public ByteBuffer createString(String name, int variability, 445 int units, String value) 446 { 447 byte[] v = getBytes(value); 448 byte[] v1 = new byte[v.length+1]; 449 System.arraycopy(v, 0, v1, 0, v.length); 450 v1[v.length] = '\0'; 451 return createByteArray(name, variability, units, v1, v1.length); 452 } 453 454 /** 455 * Create a <code>byte</code> vector entry in the instrumentation buffer 456 * with the given variability characteristic, units, and initial value. 457 * <p> 458 * The <code>maxLength</code> parameter limits the size of the byte 459 * array instrument such that the initial or subsequent updates beyond 460 * this length are silently ignored. No special handling of truncated 461 * updates is provided. 462 * <p> 463 * The underlying implementation may further limit the length of the 464 * length of the initial or subsequent value. 465 * <p> 466 * Access to the instrument is provided through the returned <code> 467 * ByteBuffer</code> object. 468 * 469 * @param variability the variability characteristic for this entry. 470 * @param units the units for this entry. 471 * @param name the name of this entry. 472 * @param value the initial value for this entry. 473 * @param maxLength the maximum length of this byte array. 474 * @return ByteBuffer a direct allocated byte buffer that allows 475 * write access to a native memory location 476 * containing a <code>long</code> value. 477 * 478 * see sun.misc.perf.Variability 479 * see sun.misc.perf.Units 480 * @see java.nio.ByteBuffer 481 */ 482 public native ByteBuffer createByteArray(String name, int variability, 483 int units, byte[] value, 484 int maxLength); 485 486 487 /** 488 * convert string to an array of UTF-8 bytes 489 */ 490 private static byte[] getBytes(String s) 491 { 492 byte[] bytes = null; 493 494 try { 495 bytes = s.getBytes("UTF-8"); 496 } 497 catch (UnsupportedEncodingException e) { 498 // ignore, UTF-8 encoding is always known 499 } 500 501 return bytes; 502 } 503 504 /** 505 * Return the value of the High Resolution Counter. 506 * 507 * The High Resolution Counter returns the number of ticks since 508 * since the start of the Java virtual machine. The resolution of 509 * the counter is machine dependent and can be determined from the 510 * value return by the {@link #highResFrequency} method. 511 * 512 * @return the number of ticks of machine dependent resolution since 513 * the start of the Java virtual machine. 514 * 515 * @see #highResFrequency 516 * @see java.lang.System#currentTimeMillis() 517 */ 518 public native long highResCounter(); 519 520 /** 521 * Returns the frequency of the High Resolution Counter, in ticks per 522 * second. 523 * 524 * This value can be used to convert the value of the High Resolution 525 * Counter, as returned from a call to the {@link #highResCounter} method, 526 * into the number of seconds since the start of the Java virtual machine. 527 * 528 * @return the frequency of the High Resolution Counter. 529 * @see #highResCounter 530 */ 531 public native long highResFrequency(); 532 533 private static native void registerNatives(); 534 535 static { 536 registerNatives(); 537 instance = new Perf(); 538 } 539 }