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
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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 }