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302 lines
9.7 KiB
302 lines
9.7 KiB
/*
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* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*/
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package java.lang.management;
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import javax.management.openmbean.CompositeData;
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import sun.management.MemoryUsageCompositeData;
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/**
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* A <tt>MemoryUsage</tt> object represents a snapshot of memory usage.
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* Instances of the <tt>MemoryUsage</tt> class are usually constructed
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* by methods that are used to obtain memory usage
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* information about individual memory pool of the Java virtual machine or
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* the heap or non-heap memory of the Java virtual machine as a whole.
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*
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* <p> A <tt>MemoryUsage</tt> object contains four values:
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* <table summary="Describes the MemoryUsage object content">
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* <tr>
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* <td valign=top> <tt>init</tt> </td>
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* <td valign=top> represents the initial amount of memory (in bytes) that
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* the Java virtual machine requests from the operating system
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* for memory management during startup. The Java virtual machine
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* may request additional memory from the operating system and
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* may also release memory to the system over time.
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* The value of <tt>init</tt> may be undefined.
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* </td>
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* </tr>
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* <tr>
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* <td valign=top> <tt>used</tt> </td>
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* <td valign=top> represents the amount of memory currently used (in bytes).
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* </td>
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* </tr>
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* <tr>
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* <td valign=top> <tt>committed</tt> </td>
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* <td valign=top> represents the amount of memory (in bytes) that is
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* guaranteed to be available for use by the Java virtual machine.
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* The amount of committed memory may change over time (increase
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* or decrease). The Java virtual machine may release memory to
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* the system and <tt>committed</tt> could be less than <tt>init</tt>.
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* <tt>committed</tt> will always be greater than
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* or equal to <tt>used</tt>.
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* </td>
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* </tr>
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* <tr>
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* <td valign=top> <tt>max</tt> </td>
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* <td valign=top> represents the maximum amount of memory (in bytes)
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* that can be used for memory management. Its value may be undefined.
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* The maximum amount of memory may change over time if defined.
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* The amount of used and committed memory will always be less than
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* or equal to <tt>max</tt> if <tt>max</tt> is defined.
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* A memory allocation may fail if it attempts to increase the
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* used memory such that <tt>used > committed</tt> even
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* if <tt>used <= max</tt> would still be true (for example,
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* when the system is low on virtual memory).
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* </td>
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* </tr>
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* </table>
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*
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* Below is a picture showing an example of a memory pool:
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*
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* <pre>
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* +----------------------------------------------+
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* +//////////////// | +
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* +//////////////// | +
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* +----------------------------------------------+
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*
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* |--------|
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* init
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* |---------------|
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* used
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* |---------------------------|
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* committed
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* |----------------------------------------------|
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* max
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* </pre>
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*
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* <h3>MXBean Mapping</h3>
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* <tt>MemoryUsage</tt> is mapped to a {@link CompositeData CompositeData}
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* with attributes as specified in the {@link #from from} method.
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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 class MemoryUsage {
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private final long init;
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private final long used;
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private final long committed;
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private final long max;
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/**
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* Constructs a <tt>MemoryUsage</tt> object.
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*
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* @param init the initial amount of memory in bytes that
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* the Java virtual machine allocates;
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* or <tt>-1</tt> if undefined.
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* @param used the amount of used memory in bytes.
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* @param committed the amount of committed memory in bytes.
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* @param max the maximum amount of memory in bytes that
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* can be used; or <tt>-1</tt> if undefined.
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*
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* @throws IllegalArgumentException if
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* <ul>
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* <li> the value of <tt>init</tt> or <tt>max</tt> is negative
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* but not <tt>-1</tt>; or</li>
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* <li> the value of <tt>used</tt> or <tt>committed</tt> is negative;
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* or</li>
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* <li> <tt>used</tt> is greater than the value of <tt>committed</tt>;
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* or</li>
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* <li> <tt>committed</tt> is greater than the value of <tt>max</tt>
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* <tt>max</tt> if defined.</li>
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* </ul>
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*/
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public MemoryUsage(long init,
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long used,
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long committed,
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long max) {
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if (init < -1) {
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throw new IllegalArgumentException( "init parameter = " +
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init + " is negative but not -1.");
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}
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if (max < -1) {
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throw new IllegalArgumentException( "max parameter = " +
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max + " is negative but not -1.");
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}
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if (used < 0) {
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throw new IllegalArgumentException( "used parameter = " +
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used + " is negative.");
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}
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if (committed < 0) {
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throw new IllegalArgumentException( "committed parameter = " +
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committed + " is negative.");
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}
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if (used > committed) {
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throw new IllegalArgumentException( "used = " + used +
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" should be <= committed = " + committed);
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}
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if (max >= 0 && committed > max) {
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throw new IllegalArgumentException( "committed = " + committed +
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" should be < max = " + max);
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}
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this.init = init;
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this.used = used;
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this.committed = committed;
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this.max = max;
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}
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/**
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* Constructs a <tt>MemoryUsage</tt> object from a
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* {@link CompositeData CompositeData}.
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*/
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private MemoryUsage(CompositeData cd) {
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// validate the input composite data
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MemoryUsageCompositeData.validateCompositeData(cd);
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this.init = MemoryUsageCompositeData.getInit(cd);
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this.used = MemoryUsageCompositeData.getUsed(cd);
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this.committed = MemoryUsageCompositeData.getCommitted(cd);
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this.max = MemoryUsageCompositeData.getMax(cd);
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}
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/**
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* Returns the amount of memory in bytes that the Java virtual machine
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* initially requests from the operating system for memory management.
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* This method returns <tt>-1</tt> if the initial memory size is undefined.
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*
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* @return the initial size of memory in bytes;
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* <tt>-1</tt> if undefined.
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*/
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public long getInit() {
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return init;
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}
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/**
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* Returns the amount of used memory in bytes.
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*
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* @return the amount of used memory in bytes.
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*
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*/
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public long getUsed() {
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return used;
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};
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/**
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* Returns the amount of memory in bytes that is committed for
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* the Java virtual machine to use. This amount of memory is
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* guaranteed for the Java virtual machine to use.
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*
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* @return the amount of committed memory in bytes.
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*
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*/
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public long getCommitted() {
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return committed;
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};
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/**
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* Returns the maximum amount of memory in bytes that can be
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* used for memory management. This method returns <tt>-1</tt>
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* if the maximum memory size is undefined.
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*
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* <p> This amount of memory is not guaranteed to be available
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* for memory management if it is greater than the amount of
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* committed memory. The Java virtual machine may fail to allocate
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* memory even if the amount of used memory does not exceed this
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* maximum size.
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*
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* @return the maximum amount of memory in bytes;
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* <tt>-1</tt> if undefined.
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*/
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public long getMax() {
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return max;
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};
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/**
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* Returns a descriptive representation of this memory usage.
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*/
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public String toString() {
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StringBuffer buf = new StringBuffer();
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buf.append("init = " + init + "(" + (init >> 10) + "K) ");
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buf.append("used = " + used + "(" + (used >> 10) + "K) ");
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buf.append("committed = " + committed + "(" +
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(committed >> 10) + "K) " );
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buf.append("max = " + max + "(" + (max >> 10) + "K)");
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return buf.toString();
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}
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/**
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* Returns a <tt>MemoryUsage</tt> object represented by the
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* given <tt>CompositeData</tt>. The given <tt>CompositeData</tt>
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* must contain the following attributes:
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*
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* <blockquote>
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* <table border summary="The attributes and the types the given CompositeData contains">
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* <tr>
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* <th align=left>Attribute Name</th>
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* <th align=left>Type</th>
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* </tr>
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* <tr>
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* <td>init</td>
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* <td><tt>java.lang.Long</tt></td>
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* </tr>
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* <tr>
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* <td>used</td>
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* <td><tt>java.lang.Long</tt></td>
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* </tr>
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* <tr>
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* <td>committed</td>
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* <td><tt>java.lang.Long</tt></td>
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* </tr>
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* <tr>
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* <td>max</td>
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* <td><tt>java.lang.Long</tt></td>
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* </tr>
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* </table>
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* </blockquote>
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*
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* @param cd <tt>CompositeData</tt> representing a <tt>MemoryUsage</tt>
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*
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* @throws IllegalArgumentException if <tt>cd</tt> does not
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* represent a <tt>MemoryUsage</tt> with the attributes described
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* above.
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*
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* @return a <tt>MemoryUsage</tt> object represented by <tt>cd</tt>
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* if <tt>cd</tt> is not <tt>null</tt>;
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* <tt>null</tt> otherwise.
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*/
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public static MemoryUsage from(CompositeData cd) {
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if (cd == null) {
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return null;
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}
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if (cd instanceof MemoryUsageCompositeData) {
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return ((MemoryUsageCompositeData) cd).getMemoryUsage();
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} else {
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return new MemoryUsage(cd);
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}
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}
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}
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