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>{@code
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 * <ul>
175 * <li>"r" - Read only access. This Java virtual machine has only
176 * read access to the instrumentation buffer for the target Java
177 * virtual machine.
178 * <li>"rw" - Read/Write access. This Java virtual machine has read and
179 * write access to the instrumentation buffer for the target Java virtual
180 * machine. This mode is currently not supported and is reserved for
181 * future enhancements.
182 * </ul>
183 *
184 * @param lvmid an integer that uniquely identifies the
185 * target local Java virtual machine.
186 * @param mode a string indicating the attach mode.
187 * @return ByteBuffer a direct allocated byte buffer
188 * @throws IllegalArgumentException The lvmid or mode was invalid.
189 * @throws IOException An I/O error occurred while trying to acquire
190 * the instrumentation buffer.
191 * @throws OutOfMemoryError The instrumentation buffer could not be mapped
192 * into the virtual machine's address space.
193 * @see java.nio.ByteBuffer
194 */
195 public ByteBuffer attach(int lvmid, String mode)
196 throws IllegalArgumentException, IOException
197 {
198 if (mode.compareTo("r") == 0) {
199 return attachImpl(null, lvmid, PERF_MODE_RO);
200 }
201 else if (mode.compareTo("rw") == 0) {
202 return attachImpl(null, lvmid, PERF_MODE_RW);
203 }
204 else {
205 throw new IllegalArgumentException("unknown mode");
206 }
207 }
208
209 /**
210 * Attach to the instrumentation buffer for the specified Java virtual
211 * machine owned by the given user.
212 * <p>
213 * This method behaves just as the <code>attach(int lvmid, String mode)
214 * </code> method, except that it only searches for Java virtual machines
215 * owned by the specified user.
216 *
217 * @param user A <code>String</code> object containing the
218 * name of the user that owns the target Java
219 * virtual machine.
220 * @param lvmid an integer that uniquely identifies the
221 * target local Java virtual machine.
222 * @param mode a string indicating the attach mode.
223 * @return ByteBuffer a direct allocated byte buffer
224 * @throws IllegalArgumentException The lvmid or mode was invalid.
225 * @throws IOException An I/O error occurred while trying to acquire
226 * the instrumentation buffer.
227 * @throws OutOfMemoryError The instrumentation buffer could not be mapped
228 * into the virtual machine's address space.
229 * @see java.nio.ByteBuffer
230 */
231 public ByteBuffer attach(String user, int lvmid, String mode)
232 throws IllegalArgumentException, IOException
233 {
234 if (mode.compareTo("r") == 0) {
235 return attachImpl(user, lvmid, PERF_MODE_RO);
236 }
237 else if (mode.compareTo("rw") == 0) {
238 return attachImpl(user, lvmid, PERF_MODE_RW);
239 }
240 else {
241 throw new IllegalArgumentException("unknown mode");
242 }
243 }
244
245 /**
246 * Call the implementation specific attach method.
247 * <p>
248 * This method calls into the Java virtual machine to perform the platform
249 * specific attach method. Buffers returned from this method are
250 * internally managed as <code>PhantomRefereces</code> to provide for
251 * guaranteed, secure release of the native resources.
252 *
253 * @param user A <code>String</code> object containing the
254 * name of the user that owns the target Java
255 * virtual machine.
256 * @param lvmid an integer that uniquely identifies the
257 * target local Java virtual machine.
258 * @param mode a string indicating the attach mode.
259 * @return ByteBuffer a direct allocated byte buffer
260 * @throws IllegalArgumentException The lvmid or mode was invalid.
261 * @throws IOException An I/O error occurred while trying to acquire
262 * the instrumentation buffer.
263 * @throws OutOfMemoryError The instrumentation buffer could not be mapped
264 * into the virtual machine's address space.
265 */
266 private ByteBuffer attachImpl(String user, int lvmid, int mode)
267 throws IllegalArgumentException, IOException
268 {
269 final ByteBuffer b = attach(user, lvmid, mode);
270
271 if (lvmid == 0) {
272 // The native instrumentation buffer for this Java virtual
273 // machine is never unmapped.
274 return b;
275 }
276 else {
277 // This is an instrumentation buffer for another Java virtual
278 // machine with native resources that need to be managed. We
279 // create a duplicate of the native ByteBuffer and manage it
280 // with a Cleaner object (PhantomReference). When the duplicate
281 // becomes only phantomly reachable, the native resources will
282 // be released.
283
284 final ByteBuffer dup = b.duplicate();
285 Cleaner.create(dup, new Runnable() {
286 public void run() {
287 try {
288 instance.detach(b);
289 }
290 catch (Throwable th) {
291 // avoid crashing the reference handler thread,
292 // but provide for some diagnosability
293 assert false : th.toString();
294 }
295 }
296 });
297 return dup;
298 }
299 }
300
301 /**
302 * Native method to perform the implementation specific attach mechanism.
303 * <p>
304 * The implementation of this method may return distinct or identical
305 * <code>ByteBuffer</code> objects for two distinct calls requesting
306 * attachment to the same Java virtual machine.
307 * <p>
308 * For the Sun HotSpot JVM, two distinct calls to attach to the same
309 * target Java virtual machine will result in two distinct ByteBuffer
310 * objects returned by this method. This may change in a future release.
311 *
312 * @param user A <code>String</code> object containing the
313 * name of the user that owns the target Java
314 * virtual machine.
315 * @param lvmid an integer that uniquely identifies the
316 * target local Java virtual machine.
317 * @param mode a string indicating the attach mode.
318 * @return ByteBuffer a direct allocated byte buffer
319 * @throws IllegalArgumentException The lvmid or mode was invalid.
320 * @throws IOException An I/O error occurred while trying to acquire
321 * the instrumentation buffer.
322 * @throws OutOfMemoryError The instrumentation buffer could not be mapped
323 * into the virtual machine's address space.
324 */
325 private native ByteBuffer attach(String user, int lvmid, int mode)
326 throws IllegalArgumentException, IOException;
327
328 /**
329 * Native method to perform the implementation specific detach mechanism.
330 * <p>
331 * If this method is passed a <code>ByteBuffer</code> object that is
332 * not created by the <code>attach</code> method, then the results of
333 * this method are undefined, with unpredictable and potentially damaging
334 * effects to the Java virtual machine. To prevent accidental or malicious
335 * use of this method, all native ByteBuffer created by the <code>
336 * attach</code> method are managed internally as PhantomReferences
337 * and resources are freed by the system.
338 * <p>
339 * If this method is passed a <code>ByteBuffer</code> object created
340 * by the <code>attach</code> method with a lvmid for the Java virtual
341 * machine running this method (lvmid=0, for example), then the detach
342 * request is silently ignored.
343 *
344 * @param ByteBuffer A direct allocated byte buffer created by the
345 * <code>attach</code> method.
346 * @see java.nio.ByteBuffer
347 * @see #attach
348 */
349 private native void detach(ByteBuffer bb);
350
351 /**
352 * Create a <code>long</code> scalar entry in the instrumentation buffer
353 * with the given variability characteristic, units, and initial value.
354 * <p>
355 * Access to the instrument is provided through the returned <code>
356 * ByteBuffer</code> object. Typically, this object should be wrapped
357 * with <code>LongBuffer</code> view object.
358 *
359 * @param variability the variability characteristic for this entry.
360 * @param units the units for this entry.
361 * @param name the name of this entry.
362 * @param value the initial value for this entry.
363 * @return ByteBuffer a direct allocated ByteBuffer object that
364 * allows write access to a native memory location
365 * containing a <code>long</code> value.
366 *
367 * see sun.misc.perf.Variability
368 * see sun.misc.perf.Units
369 * @see java.nio.ByteBuffer
370 */
371 public native ByteBuffer createLong(String name, int variability,
372 int units, long value);
373
374 /**
375 * Create a <code>String</code> entry in the instrumentation buffer with
376 * the given variability characteristic, units, and initial value.
377 * <p>
378 * The maximum length of the <code>String</code> stored in this string
379 * instrument is given in by <code>maxLength</code> parameter. Updates
380 * to this instrument with <code>String</code> values with lengths greater
381 * than <code>maxLength</code> will be truncated to <code>maxLength</code>.
382 * The truncated value will be terminated by a null character.
383 * <p>
384 * The underlying implementation may further limit the length of the
385 * value, but will continue to preserve the null terminator.
386 * <p>
387 * Access to the instrument is provided through the returned <code>
388 * ByteBuffer</code> object.
389 *
390 * @param variability the variability characteristic for this entry.
391 * @param units the units for this entry.
392 * @param name the name of this entry.
393 * @param value the initial value for this entry.
394 * @param maxLength the maximum string length for this string
395 * instrument.
396 * @return ByteBuffer a direct allocated ByteBuffer that allows
397 * write access to a native memory location
398 * containing a <code>long</code> value.
399 *
400 * see sun.misc.perf.Variability
401 * see sun.misc.perf.Units
402 * @see java.nio.ByteBuffer
403 */
404 public ByteBuffer createString(String name, int variability,
405 int units, String value, int maxLength)
406 {
407 byte[] v = getBytes(value);
408 byte[] v1 = new byte[v.length+1];
409 System.arraycopy(v, 0, v1, 0, v.length);
410 v1[v.length] = '\0';
411 return createByteArray(name, variability, units, v1, Math.max(v1.length, maxLength));
412 }
413
414 /**
415 * Create a <code>String</code> entry in the instrumentation buffer with
416 * the given variability characteristic, units, and initial value.
417 * <p>
418 * The maximum length of the <code>String</code> stored in this string
419 * instrument is implied by the length of the <code>value</code> parameter.
420 * Subsequent updates to the value of this instrument will be truncated
421 * to this implied maximum length. The truncated value will be terminated
422 * by a null character.
423 * <p>
424 * The underlying implementation may further limit the length of the
425 * initial or subsequent value, but will continue to preserve the null
426 * terminator.
427 * <p>
428 * Access to the instrument is provided through the returned <code>
429 * ByteBuffer</code> object.
430 *
431 * @param variability the variability characteristic for this entry.
432 * @param units the units for this entry.
433 * @param name the name of this entry.
434 * @param value the initial value for this entry.
435 * @return ByteBuffer a direct allocated ByteBuffer that allows
436 * write access to a native memory location
437 * containing a <code>long</code> value.
438 *
439 * see sun.misc.perf.Variability
440 * see sun.misc.perf.Units
441 * @see java.nio.ByteBuffer
442 */
443 public ByteBuffer createString(String name, int variability,
444 int units, String value)
445 {
446 byte[] v = getBytes(value);
447 byte[] v1 = new byte[v.length+1];
448 System.arraycopy(v, 0, v1, 0, v.length);
449 v1[v.length] = '\0';
450 return createByteArray(name, variability, units, v1, v1.length);
451 }
452
453 /**
454 * Create a <code>byte</code> vector entry in the instrumentation buffer
455 * with the given variability characteristic, units, and initial value.
456 * <p>
457 * The <code>maxLength</code> parameter limits the size of the byte
458 * array instrument such that the initial or subsequent updates beyond
459 * this length are silently ignored. No special handling of truncated
460 * updates is provided.
461 * <p>
462 * The underlying implementation may further limit the length of the
463 * length of the initial or subsequent value.
464 * <p>
465 * Access to the instrument is provided through the returned <code>
466 * ByteBuffer</code> object.
467 *
468 * @param variability the variability characteristic for this entry.
469 * @param units the units for this entry.
470 * @param name the name of this entry.
471 * @param value the initial value for this entry.
472 * @param maxLength the maximum length of this byte array.
473 * @return ByteBuffer a direct allocated byte buffer that allows
474 * write access to a native memory location
475 * containing a <code>long</code> value.
476 *
477 * see sun.misc.perf.Variability
478 * see sun.misc.perf.Units
479 * @see java.nio.ByteBuffer
480 */
481 public native ByteBuffer createByteArray(String name, int variability,
482 int units, byte[] value,
483 int maxLength);
484
485
486 /**
487 * convert string to an array of UTF-8 bytes
488 */
489 private static byte[] getBytes(String s)
490 {
491 byte[] bytes = null;
492
493 try {
494 bytes = s.getBytes("UTF-8");
495 }
496 catch (UnsupportedEncodingException e) {
497 // ignore, UTF-8 encoding is always known
498 }
499
500 return bytes;
501 }
502
503 /**
504 * Return the value of the High Resolution Counter.
505 *
506 * The High Resolution Counter returns the number of ticks since
507 * since the start of the Java virtual machine. The resolution of
508 * the counter is machine dependent and can be determined from the
509 * value return by the {@link #highResFrequency} method.
510 *
511 * @return the number of ticks of machine dependent resolution since
512 * the start of the Java virtual machine.
513 *
514 * @see #highResFrequency
515 * @see java.lang.System#currentTimeMillis()
516 */
517 public native long highResCounter();
518
519 /**
520 * Returns the frequency of the High Resolution Counter, in ticks per
521 * second.
522 *
523 * This value can be used to convert the value of the High Resolution
524 * Counter, as returned from a call to the {@link #highResCounter} method,
525 * into the number of seconds since the start of the Java virtual machine.
526 *
527 * @return the frequency of the High Resolution Counter.
528 * @see #highResCounter
529 */
530 public native long highResFrequency();
531
532 private static native void registerNatives();
533
534 static {
535 registerNatives();
536 instance = new Perf();
537 }
538 }