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
26 package java.lang.management;
27
28 /**
29 * The management interface for a memory pool. A memory pool
30 * represents the memory resource managed by the Java virtual machine
31 * and is managed by one or more {@link MemoryManagerMXBean memory managers}.
32 *
33 * <p> A Java virtual machine has one or more instances of the
34 * implementation class of this interface. An instance
35 * implementing this interface is
36 * an <a href="ManagementFactory.html#MXBean">MXBean</a>
37 * that can be obtained by calling
38 * the {@link ManagementFactory#getMemoryPoolMXBeans} method or
39 * from the {@link ManagementFactory#getPlatformMBeanServer
40 * platform <tt>MBeanServer</tt>} method.
41 *
42 * <p>The <tt>ObjectName</tt> for uniquely identifying the MXBean for
43 * a memory pool within an <tt>MBeanServer</tt> is:
44 * <blockquote>
45 * {@link ManagementFactory#MEMORY_POOL_MXBEAN_DOMAIN_TYPE
46 * <tt>java.lang:type=MemoryPool</tt>}<tt>,name=</tt><i>pool's name</i>
47 * </blockquote>
48 *
49 * It can be obtained by calling the
50 * {@link PlatformManagedObject#getObjectName} method.
51 *
52 * <h3>Memory Type</h3>
53 * <p>The Java virtual machine has a heap for object allocation and also
54 * maintains non-heap memory for the method area and the Java virtual
55 * machine execution. The Java virtual machine can have one or more
56 * memory pools. Each memory pool represents a memory area
57 * of one of the following types:
58 * <ul>
59 * <li>{@link MemoryType#HEAP heap}</li>
60 * <li>{@link MemoryType#NON_HEAP non-heap}</li>
61 * </ul>
62 *
63 * <h3>Memory Usage Monitoring</h3>
64 *
65 * A memory pool has the following attributes:
66 * <ul>
219 * } catch (InterruptException e) {
220 * ....
221 * }
222 * }
223 *
224 * // Do some processing such as check for memory usage
225 * // and issue a warning
226 * ....
227 *
228 * // Gets the current threshold count. The busy loop will then
229 * // ignore any crossing of threshold happens during the processing.
230 * prevCrossingCount = pool.getUsageThresholdCount();
231 * }
232 * </pre><hr>
233 * </li>
234 * <li><a name="ThresholdNotification"><b>Usage Threshold Notifications</b></a>
235 * <p>
236 * Usage threshold notification will be emitted by {@link MemoryMXBean}.
237 * When the Java virtual machine detects that the memory usage of
238 * a memory pool has reached or exceeded the usage threshold
239 * the virtual machine will trigger the <tt>MemoryMXBean</tt> to emit an
240 * {@link MemoryNotificationInfo#MEMORY_THRESHOLD_EXCEEDED
241 * usage threshold exceeded notification}.
242 * Another usage threshold exceeded notification will not be
243 * generated until the usage has fallen below the threshold and
244 * then exceeded it again.
245 * <p>
246 * Below is an example code implementing the same logic as the
247 * first example above but using the usage threshold notification
248 * mechanism to detect low memory conditions instead of polling.
249 * In this example code, upon receiving notification, the notification
250 * listener notifies another thread to perform the actual action
251 * such as to redistribute outstanding tasks, stop receiving tasks,
252 * or resume receiving tasks.
253 * The <tt>handleNotification</tt> method should be designed to
254 * do a very minimal amount of work and return without delay to avoid
255 * causing delay in delivering subsequent notifications. Time-consuming
256 * actions should be performed by a separate thread.
257 * The notification listener may be invoked by multiple threads
258 * concurrently; so the tasks performed by the listener
259 * should be properly synchronized.
260 *
261 * <pre>
262 * class MyListener implements javax.management.NotificationListener {
263 * public void handleNotification(Notification notification, Object handback) {
264 * String notifType = notification.getType();
265 * if (notifType.equals(MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED)) {
266 * // potential low memory, notify another thread
267 * // to redistribute outstanding tasks to other VMs
268 * // and stop receiving new tasks.
269 * lowMemory = true;
270 * notifyAnotherThread(lowMemory);
271 * }
272 * }
273 * }
274 *
275 * // Register MyListener with MemoryMXBean
276 * MemoryMXBean mbean = ManagementFactory.getMemoryMXBean();
277 * NotificationEmitter emitter = (NotificationEmitter) mbean;
278 * MyListener listener = new MyListener();
279 * emitter.addNotificationListener(listener, null, null);
280 *
281 * // Assume this pool supports a usage threshold.
282 * // Set the threshold to myThreshold above which no new tasks
283 * // should be taken.
284 * pool.setUsageThreshold(myThreshold);
285 *
286 * // Usage threshold detection is enabled and notification will be
287 * // handled by MyListener. Continue for other processing.
288 * ....
289 *
290 * </pre>
291 * <hr>
292 * <p>
293 * There is no guarantee about when the <tt>MemoryMXBean</tt> will emit
294 * a threshold notification and when the notification will be delivered.
295 * When a notification listener is invoked, the memory usage of
296 * the memory pool may have crossed the usage threshold more
297 * than once.
298 * The {@link MemoryNotificationInfo#getCount} method returns the number
299 * of times that the memory usage has crossed the usage threshold
300 * at the point in time when the notification was constructed.
301 * It can be compared with the current usage threshold count returned
302 * by the {@link #getUsageThresholdCount} method to determine if
303 * such situation has occurred.
304 * </li>
305 * </ol>
306 *
307 * <h3><a name="CollectionThreshold">4. Collection Usage Threshold</a></h3>
308 *
309 * Collection usage threshold is a manageable attribute only applicable
310 * to some garbage-collected memory pools.
311 * After a Java virtual machine has expended effort in reclaiming memory
312 * space by recycling unused objects in a memory pool at garbage collection
313 * time, some number of bytes in the memory pools that are garbaged
357 * JMX Specification.</a>
358 * @see <a href="package-summary.html#examples">
359 * Ways to Access MXBeans</a>
360 *
361 * @author Mandy Chung
362 * @since 1.5
363 */
364 public interface MemoryPoolMXBean extends PlatformManagedObject {
365 /**
366 * Returns the name representing this memory pool.
367 *
368 * @return the name of this memory pool.
369 */
370 public String getName();
371
372 /**
373 * Returns the type of this memory pool.
374 *
375 * <p>
376 * <b>MBeanServer access</b>:<br>
377 * The mapped type of <tt>MemoryType</tt> is <tt>String</tt>
378 * and the value is the name of the <tt>MemoryType</tt>.
379 *
380 * @return the type of this memory pool.
381 */
382 public MemoryType getType();
383
384 /**
385 * Returns an estimate of the memory usage of this memory pool.
386 * This method returns <tt>null</tt>
387 * if this memory pool is not valid (i.e. no longer exists).
388 *
389 * <p>
390 * This method requests the Java virtual machine to make
391 * a best-effort estimate of the current memory usage of this
392 * memory pool. For some memory pools, this method may be an
393 * expensive operation that requires some computation to determine
394 * the estimate. An implementation should document when
395 * this is the case.
396 *
397 * <p>This method is designed for use in monitoring system
398 * memory usage and detecting low memory condition.
399 *
400 * <p>
401 * <b>MBeanServer access</b>:<br>
402 * The mapped type of <tt>MemoryUsage</tt> is
403 * <tt>CompositeData</tt> with attributes as specified in
404 * {@link MemoryUsage#from MemoryUsage}.
405 *
406 * @return a {@link MemoryUsage} object; or <tt>null</tt> if
407 * this pool not valid.
408 */
409 public MemoryUsage getUsage();
410
411 /**
412 * Returns the peak memory usage of this memory pool since the
413 * Java virtual machine was started or since the peak was reset.
414 * This method returns <tt>null</tt>
415 * if this memory pool is not valid (i.e. no longer exists).
416 *
417 * <p>
418 * <b>MBeanServer access</b>:<br>
419 * The mapped type of <tt>MemoryUsage</tt> is
420 * <tt>CompositeData</tt> with attributes as specified in
421 * {@link MemoryUsage#from MemoryUsage}.
422 *
423 * @return a {@link MemoryUsage} object representing the peak
424 * memory usage; or <tt>null</tt> if this pool is not valid.
425 *
426 */
427 public MemoryUsage getPeakUsage();
428
429 /**
430 * Resets the peak memory usage statistic of this memory pool
431 * to the current memory usage.
432 *
433 * @throws java.lang.SecurityException if a security manager
434 * exists and the caller does not have
435 * ManagementPermission("control").
436 */
437 public void resetPeakUsage();
438
439 /**
440 * Tests if this memory pool is valid in the Java virtual
441 * machine. A memory pool becomes invalid once the Java virtual
442 * machine removes it from the memory system.
443 *
444 * @return <tt>true</tt> if the memory pool is valid in the running
445 * Java virtual machine;
446 * <tt>false</tt> otherwise.
447 */
448 public boolean isValid();
449
450 /**
451 * Returns the name of memory managers that manages this memory pool.
452 * Each memory pool will be managed by at least one memory manager.
453 *
454 * @return an array of <tt>String</tt> objects, each is the name of
455 * a memory manager managing this memory pool.
456 */
457 public String[] getMemoryManagerNames();
458
459 /**
460 * Returns the usage threshold value of this memory pool in bytes.
461 * Each memory pool has a platform-dependent default threshold value.
462 * The current usage threshold can be changed via the
463 * {@link #setUsageThreshold setUsageThreshold} method.
464 *
465 * @return the usage threshold value of this memory pool in bytes.
466 *
467 * @throws UnsupportedOperationException if this memory pool
468 * does not support a usage threshold.
469 *
470 * @see #isUsageThresholdSupported
471 */
472 public long getUsageThreshold();
473
474 /**
475 * Sets the threshold of this memory pool to the given <tt>threshold</tt>
476 * value if this memory pool supports the usage threshold.
477 * The usage threshold crossing checking is enabled in this memory pool
478 * if the threshold is set to a positive value.
479 * The usage threshold crossing checking is disabled
480 * if it is set to zero.
481 *
482 * @param threshold the new threshold value in bytes. Must be non-negative.
483 *
484 * @throws IllegalArgumentException if <tt>threshold</tt> is negative
485 * or greater than the maximum amount of memory for
486 * this memory pool if defined.
487 *
488 * @throws UnsupportedOperationException if this memory pool
489 * does not support a usage threshold.
490 *
491 * @throws java.lang.SecurityException if a security manager
492 * exists and the caller does not have
493 * ManagementPermission("control").
494 *
495 * @see #isUsageThresholdSupported
496 * @see <a href="#UsageThreshold">Usage threshold</a>
497 */
498 public void setUsageThreshold(long threshold);
499
500 /**
501 * Tests if the memory usage of this memory pool
502 * reaches or exceeds its usage threshold value.
503 *
504 * @return <tt>true</tt> if the memory usage of
505 * this memory pool reaches or exceeds the threshold value;
506 * <tt>false</tt> otherwise.
507 *
508 * @throws UnsupportedOperationException if this memory pool
509 * does not support a usage threshold.
510 */
511 public boolean isUsageThresholdExceeded();
512
513 /**
514 * Returns the number of times that the memory usage has crossed
515 * the usage threshold.
516 *
517 * @return the number of times that the memory usage
518 * has crossed its usage threshold value.
519 *
520 * @throws UnsupportedOperationException if this memory pool
521 * does not support a usage threshold.
522 */
523 public long getUsageThresholdCount();
524
525 /**
526 * Tests if this memory pool supports usage threshold.
527 *
528 * @return <tt>true</tt> if this memory pool supports usage threshold;
529 * <tt>false</tt> otherwise.
530 */
531 public boolean isUsageThresholdSupported();
532
533 /**
534 * Returns the collection usage threshold value of this memory pool
535 * in bytes. The default value is zero. The collection usage
536 * threshold can be changed via the
537 * {@link #setCollectionUsageThreshold setCollectionUsageThreshold} method.
538 *
539 * @return the collection usage threshold of this memory pool in bytes.
540 *
541 * @throws UnsupportedOperationException if this memory pool
542 * does not support a collection usage threshold.
543 *
544 * @see #isCollectionUsageThresholdSupported
545 */
546 public long getCollectionUsageThreshold();
547
548 /**
549 * Sets the collection usage threshold of this memory pool to
550 * the given <tt>threshold</tt> value.
551 * When this threshold is set to positive, the Java virtual machine
552 * will check the memory usage at its best appropriate time after it has
553 * expended effort in recycling unused objects in this memory pool.
554 * <p>
555 * The collection usage threshold crossing checking is enabled
556 * in this memory pool if the threshold is set to a positive value.
557 * The collection usage threshold crossing checking is disabled
558 * if it is set to zero.
559 *
560 * @param threshold the new collection usage threshold value in bytes.
561 * Must be non-negative.
562 *
563 * @throws IllegalArgumentException if <tt>threshold</tt> is negative
564 * or greater than the maximum amount of memory for
565 * this memory pool if defined.
566 *
567 * @throws UnsupportedOperationException if this memory pool
568 * does not support a collection usage threshold.
569 *
570 * @throws java.lang.SecurityException if a security manager
571 * exists and the caller does not have
572 * ManagementPermission("control").
573 *
574 * @see #isCollectionUsageThresholdSupported
575 * @see <a href="#CollectionThreshold">Collection usage threshold</a>
576 */
577 public void setCollectionUsageThreshold(long threshold);
578
579 /**
580 * Tests if the memory usage of this memory pool after
581 * the most recent collection on which the Java virtual
582 * machine has expended effort has reached or
583 * exceeded its collection usage threshold.
584 * This method does not request the Java virtual
585 * machine to perform any garbage collection other than its normal
586 * automatic memory management.
587 *
588 * @return <tt>true</tt> if the memory usage of this memory pool
589 * reaches or exceeds the collection usage threshold value
590 * in the most recent collection;
591 * <tt>false</tt> otherwise.
592 *
593 * @throws UnsupportedOperationException if this memory pool
594 * does not support a usage threshold.
595 */
596 public boolean isCollectionUsageThresholdExceeded();
597
598 /**
599 * Returns the number of times that the Java virtual machine
600 * has detected that the memory usage has reached or
601 * exceeded the collection usage threshold.
602 *
603 * @return the number of times that the memory
604 * usage has reached or exceeded the collection usage threshold.
605 *
606 * @throws UnsupportedOperationException if this memory pool
607 * does not support a collection usage threshold.
608 *
609 * @see #isCollectionUsageThresholdSupported
610 */
611 public long getCollectionUsageThresholdCount();
612
613 /**
614 * Returns the memory usage after the Java virtual machine
615 * most recently expended effort in recycling unused objects
616 * in this memory pool.
617 * This method does not request the Java virtual
618 * machine to perform any garbage collection other than its normal
619 * automatic memory management.
620 * This method returns <tt>null</tt> if the Java virtual
621 * machine does not support this method.
622 *
623 * <p>
624 * <b>MBeanServer access</b>:<br>
625 * The mapped type of <tt>MemoryUsage</tt> is
626 * <tt>CompositeData</tt> with attributes as specified in
627 * {@link MemoryUsage#from MemoryUsage}.
628 *
629 * @return a {@link MemoryUsage} representing the memory usage of
630 * this memory pool after the Java virtual machine most recently
631 * expended effort in recycling unused objects;
632 * <tt>null</tt> if this method is not supported.
633 */
634 public MemoryUsage getCollectionUsage();
635
636 /**
637 * Tests if this memory pool supports a collection usage threshold.
638 *
639 * @return <tt>true</tt> if this memory pool supports the
640 * collection usage threshold; <tt>false</tt> otherwise.
641 */
642 public boolean isCollectionUsageThresholdSupported();
643 }
|
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
26 package java.lang.management;
27
28 /**
29 * The management interface for a memory pool. A memory pool
30 * represents the memory resource managed by the Java virtual machine
31 * and is managed by one or more {@link MemoryManagerMXBean memory managers}.
32 *
33 * <p> A Java virtual machine has one or more instances of the
34 * implementation class of this interface. An instance
35 * implementing this interface is
36 * an <a href="ManagementFactory.html#MXBean">MXBean</a>
37 * that can be obtained by calling
38 * the {@link ManagementFactory#getMemoryPoolMXBeans} method or
39 * from the {@link ManagementFactory#getPlatformMBeanServer
40 * platform MBeanServer} method.
41 *
42 * <p>The {@code ObjectName} for uniquely identifying the MXBean for
43 * a memory pool within an {@code MBeanServer} is:
44 * <blockquote>
45 * {@link ManagementFactory#MEMORY_POOL_MXBEAN_DOMAIN_TYPE
46 * java.lang:type=MemoryPool}{@code ,name=}<i>pool's name</i>
47 * </blockquote>
48 *
49 * It can be obtained by calling the
50 * {@link PlatformManagedObject#getObjectName} method.
51 *
52 * <h3>Memory Type</h3>
53 * <p>The Java virtual machine has a heap for object allocation and also
54 * maintains non-heap memory for the method area and the Java virtual
55 * machine execution. The Java virtual machine can have one or more
56 * memory pools. Each memory pool represents a memory area
57 * of one of the following types:
58 * <ul>
59 * <li>{@link MemoryType#HEAP heap}</li>
60 * <li>{@link MemoryType#NON_HEAP non-heap}</li>
61 * </ul>
62 *
63 * <h3>Memory Usage Monitoring</h3>
64 *
65 * A memory pool has the following attributes:
66 * <ul>
219 * } catch (InterruptException e) {
220 * ....
221 * }
222 * }
223 *
224 * // Do some processing such as check for memory usage
225 * // and issue a warning
226 * ....
227 *
228 * // Gets the current threshold count. The busy loop will then
229 * // ignore any crossing of threshold happens during the processing.
230 * prevCrossingCount = pool.getUsageThresholdCount();
231 * }
232 * </pre><hr>
233 * </li>
234 * <li><a name="ThresholdNotification"><b>Usage Threshold Notifications</b></a>
235 * <p>
236 * Usage threshold notification will be emitted by {@link MemoryMXBean}.
237 * When the Java virtual machine detects that the memory usage of
238 * a memory pool has reached or exceeded the usage threshold
239 * the virtual machine will trigger the {@code MemoryMXBean} to emit an
240 * {@link MemoryNotificationInfo#MEMORY_THRESHOLD_EXCEEDED
241 * usage threshold exceeded notification}.
242 * Another usage threshold exceeded notification will not be
243 * generated until the usage has fallen below the threshold and
244 * then exceeded it again.
245 * <p>
246 * Below is an example code implementing the same logic as the
247 * first example above but using the usage threshold notification
248 * mechanism to detect low memory conditions instead of polling.
249 * In this example code, upon receiving notification, the notification
250 * listener notifies another thread to perform the actual action
251 * such as to redistribute outstanding tasks, stop receiving tasks,
252 * or resume receiving tasks.
253 * The {@code handleNotification} method should be designed to
254 * do a very minimal amount of work and return without delay to avoid
255 * causing delay in delivering subsequent notifications. Time-consuming
256 * actions should be performed by a separate thread.
257 * The notification listener may be invoked by multiple threads
258 * concurrently; so the tasks performed by the listener
259 * should be properly synchronized.
260 *
261 * <pre>
262 * class MyListener implements javax.management.NotificationListener {
263 * public void handleNotification(Notification notification, Object handback) {
264 * String notifType = notification.getType();
265 * if (notifType.equals(MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED)) {
266 * // potential low memory, notify another thread
267 * // to redistribute outstanding tasks to other VMs
268 * // and stop receiving new tasks.
269 * lowMemory = true;
270 * notifyAnotherThread(lowMemory);
271 * }
272 * }
273 * }
274 *
275 * // Register MyListener with MemoryMXBean
276 * MemoryMXBean mbean = ManagementFactory.getMemoryMXBean();
277 * NotificationEmitter emitter = (NotificationEmitter) mbean;
278 * MyListener listener = new MyListener();
279 * emitter.addNotificationListener(listener, null, null);
280 *
281 * // Assume this pool supports a usage threshold.
282 * // Set the threshold to myThreshold above which no new tasks
283 * // should be taken.
284 * pool.setUsageThreshold(myThreshold);
285 *
286 * // Usage threshold detection is enabled and notification will be
287 * // handled by MyListener. Continue for other processing.
288 * ....
289 *
290 * </pre>
291 * <hr>
292 * <p>
293 * There is no guarantee about when the {@code MemoryMXBean} will emit
294 * a threshold notification and when the notification will be delivered.
295 * When a notification listener is invoked, the memory usage of
296 * the memory pool may have crossed the usage threshold more
297 * than once.
298 * The {@link MemoryNotificationInfo#getCount} method returns the number
299 * of times that the memory usage has crossed the usage threshold
300 * at the point in time when the notification was constructed.
301 * It can be compared with the current usage threshold count returned
302 * by the {@link #getUsageThresholdCount} method to determine if
303 * such situation has occurred.
304 * </li>
305 * </ol>
306 *
307 * <h3><a name="CollectionThreshold">4. Collection Usage Threshold</a></h3>
308 *
309 * Collection usage threshold is a manageable attribute only applicable
310 * to some garbage-collected memory pools.
311 * After a Java virtual machine has expended effort in reclaiming memory
312 * space by recycling unused objects in a memory pool at garbage collection
313 * time, some number of bytes in the memory pools that are garbaged
357 * JMX Specification.</a>
358 * @see <a href="package-summary.html#examples">
359 * Ways to Access MXBeans</a>
360 *
361 * @author Mandy Chung
362 * @since 1.5
363 */
364 public interface MemoryPoolMXBean extends PlatformManagedObject {
365 /**
366 * Returns the name representing this memory pool.
367 *
368 * @return the name of this memory pool.
369 */
370 public String getName();
371
372 /**
373 * Returns the type of this memory pool.
374 *
375 * <p>
376 * <b>MBeanServer access</b>:<br>
377 * The mapped type of {@code MemoryType} is {@code String}
378 * and the value is the name of the {@code MemoryType}.
379 *
380 * @return the type of this memory pool.
381 */
382 public MemoryType getType();
383
384 /**
385 * Returns an estimate of the memory usage of this memory pool.
386 * This method returns {@code null}
387 * if this memory pool is not valid (i.e. no longer exists).
388 *
389 * <p>
390 * This method requests the Java virtual machine to make
391 * a best-effort estimate of the current memory usage of this
392 * memory pool. For some memory pools, this method may be an
393 * expensive operation that requires some computation to determine
394 * the estimate. An implementation should document when
395 * this is the case.
396 *
397 * <p>This method is designed for use in monitoring system
398 * memory usage and detecting low memory condition.
399 *
400 * <p>
401 * <b>MBeanServer access</b>:<br>
402 * The mapped type of {@code MemoryUsage} is
403 * {@code CompositeData} with attributes as specified in
404 * {@link MemoryUsage#from MemoryUsage}.
405 *
406 * @return a {@link MemoryUsage} object; or {@code null} if
407 * this pool not valid.
408 */
409 public MemoryUsage getUsage();
410
411 /**
412 * Returns the peak memory usage of this memory pool since the
413 * Java virtual machine was started or since the peak was reset.
414 * This method returns {@code null}
415 * if this memory pool is not valid (i.e. no longer exists).
416 *
417 * <p>
418 * <b>MBeanServer access</b>:<br>
419 * The mapped type of {@code MemoryUsage} is
420 * {@code CompositeData} with attributes as specified in
421 * {@link MemoryUsage#from MemoryUsage}.
422 *
423 * @return a {@link MemoryUsage} object representing the peak
424 * memory usage; or {@code null} if this pool is not valid.
425 *
426 */
427 public MemoryUsage getPeakUsage();
428
429 /**
430 * Resets the peak memory usage statistic of this memory pool
431 * to the current memory usage.
432 *
433 * @throws java.lang.SecurityException if a security manager
434 * exists and the caller does not have
435 * ManagementPermission("control").
436 */
437 public void resetPeakUsage();
438
439 /**
440 * Tests if this memory pool is valid in the Java virtual
441 * machine. A memory pool becomes invalid once the Java virtual
442 * machine removes it from the memory system.
443 *
444 * @return {@code true} if the memory pool is valid in the running
445 * Java virtual machine;
446 * {@code false} otherwise.
447 */
448 public boolean isValid();
449
450 /**
451 * Returns the name of memory managers that manages this memory pool.
452 * Each memory pool will be managed by at least one memory manager.
453 *
454 * @return an array of {@code String} objects, each is the name of
455 * a memory manager managing this memory pool.
456 */
457 public String[] getMemoryManagerNames();
458
459 /**
460 * Returns the usage threshold value of this memory pool in bytes.
461 * Each memory pool has a platform-dependent default threshold value.
462 * The current usage threshold can be changed via the
463 * {@link #setUsageThreshold setUsageThreshold} method.
464 *
465 * @return the usage threshold value of this memory pool in bytes.
466 *
467 * @throws UnsupportedOperationException if this memory pool
468 * does not support a usage threshold.
469 *
470 * @see #isUsageThresholdSupported
471 */
472 public long getUsageThreshold();
473
474 /**
475 * Sets the threshold of this memory pool to the given {@code threshold}
476 * value if this memory pool supports the usage threshold.
477 * The usage threshold crossing checking is enabled in this memory pool
478 * if the threshold is set to a positive value.
479 * The usage threshold crossing checking is disabled
480 * if it is set to zero.
481 *
482 * @param threshold the new threshold value in bytes. Must be non-negative.
483 *
484 * @throws IllegalArgumentException if {@code threshold} is negative
485 * or greater than the maximum amount of memory for
486 * this memory pool if defined.
487 *
488 * @throws UnsupportedOperationException if this memory pool
489 * does not support a usage threshold.
490 *
491 * @throws java.lang.SecurityException if a security manager
492 * exists and the caller does not have
493 * ManagementPermission("control").
494 *
495 * @see #isUsageThresholdSupported
496 * @see <a href="#UsageThreshold">Usage threshold</a>
497 */
498 public void setUsageThreshold(long threshold);
499
500 /**
501 * Tests if the memory usage of this memory pool
502 * reaches or exceeds its usage threshold value.
503 *
504 * @return {@code true} if the memory usage of
505 * this memory pool reaches or exceeds the threshold value;
506 * {@code false} otherwise.
507 *
508 * @throws UnsupportedOperationException if this memory pool
509 * does not support a usage threshold.
510 */
511 public boolean isUsageThresholdExceeded();
512
513 /**
514 * Returns the number of times that the memory usage has crossed
515 * the usage threshold.
516 *
517 * @return the number of times that the memory usage
518 * has crossed its usage threshold value.
519 *
520 * @throws UnsupportedOperationException if this memory pool
521 * does not support a usage threshold.
522 */
523 public long getUsageThresholdCount();
524
525 /**
526 * Tests if this memory pool supports usage threshold.
527 *
528 * @return {@code true} if this memory pool supports usage threshold;
529 * {@code false} otherwise.
530 */
531 public boolean isUsageThresholdSupported();
532
533 /**
534 * Returns the collection usage threshold value of this memory pool
535 * in bytes. The default value is zero. The collection usage
536 * threshold can be changed via the
537 * {@link #setCollectionUsageThreshold setCollectionUsageThreshold} method.
538 *
539 * @return the collection usage threshold of this memory pool in bytes.
540 *
541 * @throws UnsupportedOperationException if this memory pool
542 * does not support a collection usage threshold.
543 *
544 * @see #isCollectionUsageThresholdSupported
545 */
546 public long getCollectionUsageThreshold();
547
548 /**
549 * Sets the collection usage threshold of this memory pool to
550 * the given {@code threshold} value.
551 * When this threshold is set to positive, the Java virtual machine
552 * will check the memory usage at its best appropriate time after it has
553 * expended effort in recycling unused objects in this memory pool.
554 * <p>
555 * The collection usage threshold crossing checking is enabled
556 * in this memory pool if the threshold is set to a positive value.
557 * The collection usage threshold crossing checking is disabled
558 * if it is set to zero.
559 *
560 * @param threshold the new collection usage threshold value in bytes.
561 * Must be non-negative.
562 *
563 * @throws IllegalArgumentException if {@code threshold} is negative
564 * or greater than the maximum amount of memory for
565 * this memory pool if defined.
566 *
567 * @throws UnsupportedOperationException if this memory pool
568 * does not support a collection usage threshold.
569 *
570 * @throws java.lang.SecurityException if a security manager
571 * exists and the caller does not have
572 * ManagementPermission("control").
573 *
574 * @see #isCollectionUsageThresholdSupported
575 * @see <a href="#CollectionThreshold">Collection usage threshold</a>
576 */
577 public void setCollectionUsageThreshold(long threshold);
578
579 /**
580 * Tests if the memory usage of this memory pool after
581 * the most recent collection on which the Java virtual
582 * machine has expended effort has reached or
583 * exceeded its collection usage threshold.
584 * This method does not request the Java virtual
585 * machine to perform any garbage collection other than its normal
586 * automatic memory management.
587 *
588 * @return {@code true} if the memory usage of this memory pool
589 * reaches or exceeds the collection usage threshold value
590 * in the most recent collection;
591 * {@code false} otherwise.
592 *
593 * @throws UnsupportedOperationException if this memory pool
594 * does not support a usage threshold.
595 */
596 public boolean isCollectionUsageThresholdExceeded();
597
598 /**
599 * Returns the number of times that the Java virtual machine
600 * has detected that the memory usage has reached or
601 * exceeded the collection usage threshold.
602 *
603 * @return the number of times that the memory
604 * usage has reached or exceeded the collection usage threshold.
605 *
606 * @throws UnsupportedOperationException if this memory pool
607 * does not support a collection usage threshold.
608 *
609 * @see #isCollectionUsageThresholdSupported
610 */
611 public long getCollectionUsageThresholdCount();
612
613 /**
614 * Returns the memory usage after the Java virtual machine
615 * most recently expended effort in recycling unused objects
616 * in this memory pool.
617 * This method does not request the Java virtual
618 * machine to perform any garbage collection other than its normal
619 * automatic memory management.
620 * This method returns {@code null} if the Java virtual
621 * machine does not support this method.
622 *
623 * <p>
624 * <b>MBeanServer access</b>:<br>
625 * The mapped type of {@code MemoryUsage} is
626 * {@code CompositeData} with attributes as specified in
627 * {@link MemoryUsage#from MemoryUsage}.
628 *
629 * @return a {@link MemoryUsage} representing the memory usage of
630 * this memory pool after the Java virtual machine most recently
631 * expended effort in recycling unused objects;
632 * {@code null} if this method is not supported.
633 */
634 public MemoryUsage getCollectionUsage();
635
636 /**
637 * Tests if this memory pool supports a collection usage threshold.
638 *
639 * @return {@code true} if this memory pool supports the
640 * collection usage threshold; {@code false} otherwise.
641 */
642 public boolean isCollectionUsageThresholdSupported();
643 }
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