author | jfranck |
Wed, 11 Sep 2013 09:45:52 +0200 | |
changeset 19834 | c43d94c72c41 |
parent 18799 | 31062cb3cc8e |
child 21278 | ef8a3a2a72f2 |
permissions | -rw-r--r-- |
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/* |
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* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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package java.lang.management; |
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/** |
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* The management interface for a memory pool. A memory pool |
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* represents the memory resource managed by the Java virtual machine |
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* and is managed by one or more {@link MemoryManagerMXBean memory managers}. |
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* |
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* <p> A Java virtual machine has one or more instances of the |
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* implementation class of this interface. An instance |
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* implementing this interface is |
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* an <a href="ManagementFactory.html#MXBean">MXBean</a> |
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* that can be obtained by calling |
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* the {@link ManagementFactory#getMemoryPoolMXBeans} method or |
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* from the {@link ManagementFactory#getPlatformMBeanServer |
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* platform <tt>MBeanServer</tt>} method. |
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* |
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* <p>The <tt>ObjectName</tt> for uniquely identifying the MXBean for |
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* a memory pool within an <tt>MBeanServer</tt> is: |
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* <blockquote> |
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* {@link ManagementFactory#MEMORY_POOL_MXBEAN_DOMAIN_TYPE |
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* <tt>java.lang:type=MemoryPool</tt>}<tt>,name=</tt><i>pool's name</i> |
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* </blockquote> |
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* |
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* It can be obtained by calling the |
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* {@link PlatformManagedObject#getObjectName} method. |
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* |
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* <h3>Memory Type</h3> |
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* <p>The Java virtual machine has a heap for object allocation and also |
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* maintains non-heap memory for the method area and the Java virtual |
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* machine execution. The Java virtual machine can have one or more |
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* memory pools. Each memory pool represents a memory area |
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* of one of the following types: |
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* <ul> |
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* <li>{@link MemoryType#HEAP heap}</li> |
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* <li>{@link MemoryType#NON_HEAP non-heap}</li> |
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* </ul> |
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* |
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* <h3>Memory Usage Monitoring</h3> |
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* |
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* A memory pool has the following attributes: |
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* <ul> |
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* <li><a href="#Usage">Memory usage</a></li> |
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* <li><a href="#PeakUsage">Peak memory usage</a></li> |
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* <li><a href="#UsageThreshold">Usage Threshold</a></li> |
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* <li><a href="#CollectionThreshold">Collection Usage Threshold</a> |
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* (only supported by some <em>garbage-collected</em> memory pools)</li> |
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* </ul> |
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* |
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* <h3><a name="Usage">1. Memory Usage</a></h3> |
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* |
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* The {@link #getUsage} method provides an estimate |
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* of the current usage of a memory pool. |
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* For a garbage-collected memory pool, the amount of used memory |
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* includes the memory occupied by all objects in the pool |
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* including both <em>reachable</em> and <em>unreachable</em> objects. |
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* |
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* <p>In general, this method is a lightweight operation for getting |
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* an approximate memory usage. For some memory pools, for example, |
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* when objects are not packed contiguously, this method may be |
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* an expensive operation that requires some computation to determine |
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* the current memory usage. An implementation should document when |
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* this is the case. |
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* |
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* <h3><a name="PeakUsage">2. Peak Memory Usage</a></h3> |
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* |
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* The Java virtual machine maintains the peak memory usage of a memory |
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* pool since the virtual machine was started or the peak was reset. |
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* The peak memory usage is returned by the {@link #getPeakUsage} method |
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* and reset by calling the {@link #resetPeakUsage} method. |
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* |
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* <h3><a name="UsageThreshold">3. Usage Threshold</a></h3> |
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* |
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* Each memory pool has a manageable attribute |
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* called the <i>usage threshold</i> which has a default value supplied |
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* by the Java virtual machine. The default value is platform-dependent. |
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* The usage threshold can be set via the |
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* {@link #setUsageThreshold setUsageThreshold} method. |
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* If the threshold is set to a positive value, the usage threshold crossing |
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* checking is enabled in this memory pool. |
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* If the usage threshold is set to zero, usage |
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* threshold crossing checking on this memory pool is disabled. |
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* The {@link MemoryPoolMXBean#isUsageThresholdSupported} method can |
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* be used to determine if this functionality is supported. |
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* <p> |
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* A Java virtual machine performs usage threshold crossing checking on a |
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* memory pool basis at its best appropriate time, typically, |
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* at garbage collection time. |
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* Each memory pool maintains a {@link #getUsageThresholdCount |
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* usage threshold count} that will get incremented |
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* every time when the Java virtual machine |
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* detects that the memory pool usage is crossing the threshold. |
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* <p> |
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* This manageable usage threshold attribute is designed for monitoring the |
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* increasing trend of memory usage with low overhead. |
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* Usage threshold may not be appropriate for some memory pools. |
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* For example, a generational garbage collector, a common garbage collection |
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* algorithm used in many Java virtual machine implementations, |
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* manages two or more generations segregating objects by age. |
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* Most of the objects are allocated in |
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* the <em>youngest generation</em> (say a nursery memory pool). |
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* The nursery memory pool is designed to be filled up and |
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* collecting the nursery memory pool will free most of its memory space |
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* since it is expected to contain mostly short-lived objects |
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* and mostly are unreachable at garbage collection time. |
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* In this case, it is more appropriate for the nursery memory pool |
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* not to support a usage threshold. In addition, |
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* if the cost of an object allocation |
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* in one memory pool is very low (for example, just atomic pointer exchange), |
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* the Java virtual machine would probably not support the usage threshold |
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* for that memory pool since the overhead in comparing the usage with |
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* the threshold is higher than the cost of object allocation. |
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* |
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* <p> |
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* The memory usage of the system can be monitored using |
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* <a href="#Polling">polling</a> or |
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* <a href="#ThresholdNotification">threshold notification</a> mechanisms. |
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* |
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* <ol type="a"> |
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* <li><a name="Polling"><b>Polling</b></a> |
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* <p> |
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* An application can continuously monitor its memory usage |
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* by calling either the {@link #getUsage} method for all |
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* memory pools or the {@link #isUsageThresholdExceeded} method |
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* for those memory pools that support a usage threshold. |
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* Below is example code that has a thread delicated for |
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* task distribution and processing. At every interval, |
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* it will determine if it should receive and process new tasks based |
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* on its memory usage. If the memory usage exceeds its usage threshold, |
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* it will redistribute all outstanding tasks to other VMs and |
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* stop receiving new tasks until the memory usage returns |
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* below its usage threshold. |
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* |
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* <pre> |
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* // Assume the usage threshold is supported for this pool. |
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* // Set the threshold to myThreshold above which no new tasks |
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* // should be taken. |
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* pool.setUsageThreshold(myThreshold); |
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* .... |
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* |
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* boolean lowMemory = false; |
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* while (true) { |
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* if (pool.isUsageThresholdExceeded()) { |
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* // potential low memory, so redistribute tasks to other VMs |
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* lowMemory = true; |
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* redistributeTasks(); |
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* // stop receiving new tasks |
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* stopReceivingTasks(); |
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* } else { |
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* if (lowMemory) { |
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* // resume receiving tasks |
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* lowMemory = false; |
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* resumeReceivingTasks(); |
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* } |
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* // processing outstanding task |
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* ... |
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* } |
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* // sleep for sometime |
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* try { |
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* Thread.sleep(sometime); |
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* } catch (InterruptedException e) { |
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* ... |
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* } |
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* } |
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* </pre> |
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* |
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* <hr> |
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* The above example does not differentiate the case where |
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* the memory usage has temporarily dropped below the usage threshold |
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* from the case where the memory usage remains above the threshould |
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* between two iterations. The usage threshold count returned by |
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* the {@link #getUsageThresholdCount} method |
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* can be used to determine |
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* if the memory usage has returned below the threshold |
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* between two polls. |
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* <p> |
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* Below shows another example that takes some action if a |
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* memory pool is under low memory and ignores the memory usage |
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* changes during the action processing time. |
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* |
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* <pre> |
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* // Assume the usage threshold is supported for this pool. |
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* // Set the threshold to myThreshold which determines if |
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* // the application will take some action under low memory condition. |
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* pool.setUsageThreshold(myThreshold); |
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* |
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* int prevCrossingCount = 0; |
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* while (true) { |
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* // A busy loop to detect when the memory usage |
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* // has exceeded the threshold. |
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* while (!pool.isUsageThresholdExceeded() || |
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* pool.getUsageThresholdCount() == prevCrossingCount) { |
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* try { |
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* Thread.sleep(sometime) |
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* } catch (InterruptException e) { |
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* .... |
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* } |
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* } |
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* |
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* // Do some processing such as check for memory usage |
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* // and issue a warning |
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* .... |
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* |
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* // Gets the current threshold count. The busy loop will then |
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* // ignore any crossing of threshold happens during the processing. |
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* prevCrossingCount = pool.getUsageThresholdCount(); |
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* } |
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* </pre><hr> |
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* </li> |
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* <li><a name="ThresholdNotification"><b>Usage Threshold Notifications</b></a> |
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* <p> |
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* Usage threshold notification will be emitted by {@link MemoryMXBean}. |
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* When the Java virtual machine detects that the memory usage of |
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* a memory pool has reached or exceeded the usage threshold |
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* the virtual machine will trigger the <tt>MemoryMXBean</tt> to emit an |
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* {@link MemoryNotificationInfo#MEMORY_THRESHOLD_EXCEEDED |
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* usage threshold exceeded notification}. |
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* Another usage threshold exceeded notification will not be |
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* generated until the usage has fallen below the threshold and |
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* then exceeded it again. |
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* <p> |
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* Below is an example code implementing the same logic as the |
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* first example above but using the usage threshold notification |
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* mechanism to detect low memory conditions instead of polling. |
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* In this example code, upon receiving notification, the notification |
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* listener notifies another thread to perform the actual action |
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* such as to redistribute outstanding tasks, stop receiving tasks, |
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* or resume receiving tasks. |
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* The <tt>handleNotification</tt> method should be designed to |
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* do a very minimal amount of work and return without delay to avoid |
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* causing delay in delivering subsequent notifications. Time-consuming |
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* actions should be performed by a separate thread. |
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* The notification listener may be invoked by multiple threads |
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* concurrently; so the tasks performed by the listener |
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* should be properly synchronized. |
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* |
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* <pre> |
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* class MyListener implements javax.management.NotificationListener { |
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* public void handleNotification(Notification notification, Object handback) { |
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* String notifType = notification.getType(); |
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* if (notifType.equals(MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED)) { |
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* // potential low memory, notify another thread |
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* // to redistribute outstanding tasks to other VMs |
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* // and stop receiving new tasks. |
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* lowMemory = true; |
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* notifyAnotherThread(lowMemory); |
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* } |
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* } |
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* } |
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* |
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* // Register MyListener with MemoryMXBean |
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* MemoryMXBean mbean = ManagementFactory.getMemoryMXBean(); |
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* NotificationEmitter emitter = (NotificationEmitter) mbean; |
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* MyListener listener = new MyListener(); |
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* emitter.addNotificationListener(listener, null, null); |
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* |
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* // Assume this pool supports a usage threshold. |
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* // Set the threshold to myThreshold above which no new tasks |
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* // should be taken. |
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* pool.setUsageThreshold(myThreshold); |
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* |
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* // Usage threshold detection is enabled and notification will be |
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* // handled by MyListener. Continue for other processing. |
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* .... |
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* |
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* </pre> |
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* <hr> |
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* <p> |
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* There is no guarantee about when the <tt>MemoryMXBean</tt> will emit |
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* a threshold notification and when the notification will be delivered. |
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* When a notification listener is invoked, the memory usage of |
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* the memory pool may have crossed the usage threshold more |
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* than once. |
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* The {@link MemoryNotificationInfo#getCount} method returns the number |
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* of times that the memory usage has crossed the usage threshold |
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* at the point in time when the notification was constructed. |
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* It can be compared with the current usage threshold count returned |
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* by the {@link #getUsageThresholdCount} method to determine if |
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* such situation has occurred. |
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* </li> |
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* </ol> |
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* |
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* <h3><a name="CollectionThreshold">4. Collection Usage Threshold</a></h3> |
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* |
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* Collection usage threshold is a manageable attribute only applicable |
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* to some garbage-collected memory pools. |
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* After a Java virtual machine has expended effort in reclaiming memory |
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* space by recycling unused objects in a memory pool at garbage collection |
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* time, some number of bytes in the memory pools that are garbaged |
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* collected will still be in use. The collection usage threshold |
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* allows a value to be set for this number of bytes such |
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* that if the threshold is exceeded, |
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* a {@link MemoryNotificationInfo#MEMORY_THRESHOLD_EXCEEDED |
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* collection usage threshold exceeded notification} |
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* will be emitted by the {@link MemoryMXBean}. |
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* In addition, the {@link #getCollectionUsageThresholdCount |
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* collection usage threshold count} will then be incremented. |
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* |
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* <p> |
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* The {@link MemoryPoolMXBean#isCollectionUsageThresholdSupported} method can |
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* be used to determine if this functionality is supported. |
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* |
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* <p> |
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* A Java virtual machine performs collection usage threshold checking |
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* on a memory pool basis. This checking is enabled if the collection |
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* usage threshold is set to a positive value. |
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* If the collection usage threshold is set to zero, this checking |
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* is disabled on this memory pool. Default value is zero. |
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* The Java virtual machine performs the collection usage threshold |
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* checking at garbage collection time. |
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* |
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* <p> |
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* Some garbage-collected memory pools may |
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* choose not to support the collection usage threshold. For example, |
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* a memory pool is only managed by a continuous concurrent garbage |
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* collector. Objects can be allocated in this memory pool by some thread |
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* while the unused objects are reclaimed by the concurrent garbage |
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* collector simultaneously. Unless there is a well-defined |
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* garbage collection time which is the best appropriate time |
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* to check the memory usage, the collection usage threshold should not |
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* be supported. |
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* |
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* <p> |
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* The collection usage threshold is designed for monitoring the memory usage |
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* after the Java virtual machine has expended effort in reclaiming |
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* memory space. The collection usage could also be monitored |
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* by the polling and threshold notification mechanism |
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* described above for the <a href="#UsageThreshold">usage threshold</a> |
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* in a similar fashion. |
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* |
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* @see ManagementFactory#getPlatformMXBeans(Class) |
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* @see <a href="../../../javax/management/package-summary.html"> |
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* JMX Specification.</a> |
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* @see <a href="package-summary.html#examples"> |
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* Ways to Access MXBeans</a> |
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* |
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* @author Mandy Chung |
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* @since 1.5 |
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*/ |
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public interface MemoryPoolMXBean extends PlatformManagedObject { |
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/** |
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* Returns the name representing this memory pool. |
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* |
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* @return the name of this memory pool. |
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*/ |
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public String getName(); |
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/** |
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* Returns the type of this memory pool. |
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* |
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* <p> |
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* <b>MBeanServer access</b>:<br> |
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* The mapped type of <tt>MemoryType</tt> is <tt>String</tt> |
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* and the value is the name of the <tt>MemoryType</tt>. |
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* |
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* @return the type of this memory pool. |
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*/ |
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public MemoryType getType(); |
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/** |
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* Returns an estimate of the memory usage of this memory pool. |
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* This method returns <tt>null</tt> |
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* if this memory pool is not valid (i.e. no longer exists). |
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* |
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* <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 |
} |