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| 1 | /* | ||
| 2 | * Copyright (c) 2003, 2008, 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 | |||
| 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 | * <h4>Memory Type</h4> | ||
| 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 | * <h4>Memory Usage Monitoring</h4> | ||
| 64 | * | ||
| 65 | * A memory pool has the following attributes: | ||
| 66 | * <ul> | ||
| 67 | * <li><a href="#Usage">Memory usage</a></li> | ||
| 68 | * <li><a href="#PeakUsage">Peak memory usage</a></li> | ||
| 69 | * <li><a href="#UsageThreshold">Usage Threshold</a></li> | ||
| 70 | * <li><a href="#CollectionThreshold">Collection Usage Threshold</a> | ||
| 71 | * (only supported by some <em>garbage-collected</em> memory pools)</li> | ||
| 72 | * </ul> | ||
| 73 | * | ||
| 74 | * <h4><a name="Usage">1. Memory Usage</a></h4> | ||
| 75 | * | ||
| 76 | * The {@link #getUsage} method provides an estimate | ||
| 77 | * of the current usage of a memory pool. | ||
| 78 | * For a garbage-collected memory pool, the amount of used memory | ||
| 79 | * includes the memory occupied by all objects in the pool | ||
| 80 | * including both <em>reachable</em> and <em>unreachable</em> objects. | ||
| 81 | * | ||
| 82 | * <p>In general, this method is a lightweight operation for getting | ||
| 83 | * an approximate memory usage. For some memory pools, for example, | ||
| 84 | * when objects are not packed contiguously, this method may be | ||
| 85 | * an expensive operation that requires some computation to determine | ||
| 86 | * the current memory usage. An implementation should document when | ||
| 87 | * this is the case. | ||
| 88 | * | ||
| 89 | * <h4><a name="PeakUsage">2. Peak Memory Usage</a></h4> | ||
| 90 | * | ||
| 91 | * The Java virtual machine maintains the peak memory usage of a memory | ||
| 92 | * pool since the virtual machine was started or the peak was reset. | ||
| 93 | * The peak memory usage is returned by the {@link #getPeakUsage} method | ||
| 94 | * and reset by calling the {@link #resetPeakUsage} method. | ||
| 95 | * | ||
| 96 | * <h4><a name="UsageThreshold">3. Usage Threshold</a></h4> | ||
| 97 | * | ||
| 98 | * Each memory pool has a manageable attribute | ||
| 99 | * called the <i>usage threshold</i> which has a default value supplied | ||
| 100 | * by the Java virtual machine. The default value is platform-dependent. | ||
| 101 | * The usage threshold can be set via the | ||
| 102 | * {@link #setUsageThreshold setUsageThreshold} method. | ||
| 103 | * If the threshold is set to a positive value, the usage threshold crossing | ||
| 104 | * checking is enabled in this memory pool. | ||
| 105 | * If the usage threshold is set to zero, usage | ||
| 106 | * threshold crossing checking on this memory pool is disabled. | ||
| 107 | * The {@link MemoryPoolMXBean#isUsageThresholdSupported} method can | ||
| 108 | * be used to determine if this functionality is supported. | ||
| 109 | * <p> | ||
| 110 | * A Java virtual machine performs usage threshold crossing checking on a | ||
| 111 | * memory pool basis at its best appropriate time, typically, | ||
| 112 | * at garbage collection time. | ||
| 113 | * Each memory pool maintains a {@link #getUsageThresholdCount | ||
| 114 | * usage threshold count} that will get incremented | ||
| 115 | * every time when the Java virtual machine | ||
| 116 | * detects that the memory pool usage is crossing the threshold. | ||
| 117 | * <p> | ||
| 118 | * This manageable usage threshold attribute is designed for monitoring the | ||
| 119 | * increasing trend of memory usage with low overhead. | ||
| 120 | * Usage threshold may not be appropriate for some memory pools. | ||
| 121 | * For example, a generational garbage collector, a common garbage collection | ||
| 122 | * algorithm used in many Java virtual machine implementations, | ||
| 123 | * manages two or more generations segregating objects by age. | ||
| 124 | * Most of the objects are allocated in | ||
| 125 | * the <em>youngest generation</em> (say a nursery memory pool). | ||
| 126 | * The nursery memory pool is designed to be filled up and | ||
| 127 | * collecting the nursery memory pool will free most of its memory space | ||
| 128 | * since it is expected to contain mostly short-lived objects | ||
| 129 | * and mostly are unreachable at garbage collection time. | ||
| 130 | * In this case, it is more appropriate for the nursery memory pool | ||
| 131 | * not to support a usage threshold. In addition, | ||
| 132 | * if the cost of an object allocation | ||
| 133 | * in one memory pool is very low (for example, just atomic pointer exchange), | ||
| 134 | * the Java virtual machine would probably not support the usage threshold | ||
| 135 | * for that memory pool since the overhead in comparing the usage with | ||
| 136 | * the threshold is higher than the cost of object allocation. | ||
| 137 | * | ||
| 138 | * <p> | ||
| 139 | * The memory usage of the system can be monitored using | ||
| 140 | * <a href="#Polling">polling</a> or | ||
| 141 | * <a href="#ThresholdNotification">threshold notification</a> mechanisms. | ||
| 142 | * | ||
| 143 | * <ol type="a"> | ||
| 144 | * <li><a name="Polling"><b>Polling</b></a> | ||
| 145 | * <p> | ||
| 146 | * An application can continuously monitor its memory usage | ||
| 147 | * by calling either the {@link #getUsage} method for all | ||
| 148 | * memory pools or the {@link #isUsageThresholdExceeded} method | ||
| 149 | * for those memory pools that support a usage threshold. | ||
| 150 | * Below is example code that has a thread delicated for | ||
| 151 | * task distribution and processing. At every interval, | ||
| 152 | * it will determine if it should receive and process new tasks based | ||
| 153 | * on its memory usage. If the memory usage exceeds its usage threshold, | ||
| 154 | * it will redistribute all outstanding tasks to other VMs and | ||
| 155 | * stop receiving new tasks until the memory usage returns | ||
| 156 | * below its usage threshold. | ||
| 157 | * | ||
| 158 | * <pre> | ||
| 159 | * // Assume the usage threshold is supported for this pool. | ||
| 160 | * // Set the threshold to myThreshold above which no new tasks | ||
| 161 | * // should be taken. | ||
| 162 | * pool.setUsageThreshold(myThreshold); | ||
| 163 | * .... | ||
| 164 | * | ||
| 165 | * boolean lowMemory = false; | ||
| 166 | * while (true) { | ||
| 167 | * if (pool.isUsageThresholdExceeded()) { | ||
| 168 | * // potential low memory, so redistribute tasks to other VMs | ||
| 169 | * lowMemory = true; | ||
| 170 | * redistributeTasks(); | ||
| 171 | * // stop receiving new tasks | ||
| 172 | * stopReceivingTasks(); | ||
| 173 | * } else { | ||
| 174 | * if (lowMemory) { | ||
| 175 | * // resume receiving tasks | ||
| 176 | * lowMemory = false; | ||
| 177 | * resumeReceivingTasks(); | ||
| 178 | * } | ||
| 179 | * // processing outstanding task | ||
| 180 | * ... | ||
| 181 | * } | ||
| 182 | * // sleep for sometime | ||
| 183 | * try { | ||
| 184 | * Thread.sleep(sometime); | ||
| 185 | * } catch (InterruptedException e) { | ||
| 186 | * ... | ||
| 187 | * } | ||
| 188 | * } | ||
| 189 | * </pre> | ||
| 190 | * | ||
| 191 | * <hr> | ||
| 192 | * The above example does not differentiate the case where | ||
| 193 | * the memory usage has temporarily dropped below the usage threshold | ||
| 194 | * from the case where the memory usage remains above the threshould | ||
| 195 | * between two iterations. The usage threshold count returned by | ||
| 196 | * the {@link #getUsageThresholdCount} method | ||
| 197 | * can be used to determine | ||
| 198 | * if the memory usage has returned below the threshold | ||
| 199 | * between two polls. | ||
| 200 | * <p> | ||
| 201 | * Below shows another example that takes some action if a | ||
| 202 | * memory pool is under low memory and ignores the memory usage | ||
| 203 | * changes during the action processing time. | ||
| 204 | * | ||
| 205 | * <pre> | ||
| 206 | * // Assume the usage threshold is supported for this pool. | ||
| 207 | * // Set the threshold to myThreshold which determines if | ||
| 208 | * // the application will take some action under low memory condition. | ||
| 209 | * pool.setUsageThreshold(myThreshold); | ||
| 210 | * | ||
| 211 | * int prevCrossingCount = 0; | ||
| 212 | * while (true) { | ||
| 213 | * // A busy loop to detect when the memory usage | ||
| 214 | * // has exceeded the threshold. | ||
| 215 | * while (!pool.isUsageThresholdExceeded() || | ||
| 216 | * pool.getUsageThresholdCount() == prevCrossingCount) { | ||
| 217 | * try { | ||
| 218 | * Thread.sleep(sometime) | ||
| 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 | * <h4><a name="CollectionThreshold">4. Collection Usage Threshold</a></h4> | ||
| 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 | ||
| 314 | * collected will still be in use. The collection usage threshold | ||
| 315 | * allows a value to be set for this number of bytes such | ||
| 316 | * that if the threshold is exceeded, | ||
| 317 | * a {@link MemoryNotificationInfo#MEMORY_THRESHOLD_EXCEEDED | ||
| 318 | * collection usage threshold exceeded notification} | ||
| 319 | * will be emitted by the {@link MemoryMXBean}. | ||
| 320 | * In addition, the {@link #getCollectionUsageThresholdCount | ||
| 321 | * collection usage threshold count} will then be incremented. | ||
| 322 | * | ||
| 323 | * <p> | ||
| 324 | * The {@link MemoryPoolMXBean#isCollectionUsageThresholdSupported} method can | ||
| 325 | * be used to determine if this functionality is supported. | ||
| 326 | * | ||
| 327 | * <p> | ||
| 328 | * A Java virtual machine performs collection usage threshold checking | ||
| 329 | * on a memory pool basis. This checking is enabled if the collection | ||
| 330 | * usage threshold is set to a positive value. | ||
| 331 | * If the collection usage threshold is set to zero, this checking | ||
| 332 | * is disabled on this memory pool. Default value is zero. | ||
| 333 | * The Java virtual machine performs the collection usage threshold | ||
| 334 | * checking at garbage collection time. | ||
| 335 | * | ||
| 336 | * <p> | ||
| 337 | * Some garbage-collected memory pools may | ||
| 338 | * choose not to support the collection usage threshold. For example, | ||
| 339 | * a memory pool is only managed by a continuous concurrent garbage | ||
| 340 | * collector. Objects can be allocated in this memory pool by some thread | ||
| 341 | * while the unused objects are reclaimed by the concurrent garbage | ||
| 342 | * collector simultaneously. Unless there is a well-defined | ||
| 343 | * garbage collection time which is the best appropriate time | ||
| 344 | * to check the memory usage, the collection usage threshold should not | ||
| 345 | * be supported. | ||
| 346 | * | ||
| 347 | * <p> | ||
| 348 | * The collection usage threshold is designed for monitoring the memory usage | ||
| 349 | * after the Java virtual machine has expended effort in reclaiming | ||
| 350 | * memory space. The collection usage could also be monitored | ||
| 351 | * by the polling and threshold notification mechanism | ||
| 352 | * described above for the <a href="#UsageThreshold">usage threshold</a> | ||
| 353 | * in a similar fashion. | ||
| 354 | * | ||
| 355 | * @see ManagementFactory#getPlatformMXBeans(Class) | ||
| 356 | * @see <a href="../../../javax/management/package-summary.html"> | ||
| 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 | } | ||