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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 | +} | |