Java类MemoryUsage，通过MemoryUsage可以查看Java 虚拟机的内存池的内存使用情况。
MemoryUsage类有四个值（均以字节为单位）：
Init：java虚拟机在启动的时候向操作系统请求的初始内存容量，java虚拟机在运行的过程中可能向操作系统请求更多的内存或将内存释放给操作系统，所以init的值是不确定的。
Used：当前已经使用的内存量。
Committed：表示保证java虚拟机能使用的内存量，已提交的内存量可以随时间而变化（增加或减少）。Java 虚拟机可能会将内存释放给系统，committed 可以小于 init。committed 将始终大于或等于 used。
Max：表示可以用于内存管理的最大内存量（以字节为单位）。可以不定义其值。如果定义了该值，最大内存量可能随时间而更改。已使用的内存量和已提 交的内存量将始终小于或等于 max（如果定义了 max）。如果内存分配试图增加满足以下条件的已使用内存将会失败：used > committed，即使 used <= max 仍然为 true（例如，当系统的虚拟内存不足时）。
直接看demo吧！
在实际开发中，一般可以用这个监控线程占用内存使用情况。
import java.lang.management.ManagementFactory;import java.lang.management.MemoryUsage;public class MemoryUseTest { public String getMemoryUseInfo(){
MemoryUsage mu = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage(); long getCommitted = mu.getCommitted(); long getInit = mu.getInit(); long getUsed = mu.getUsed(); long max = mu.getMax(); return ">>getCommitted(MB)=>" + getCommitted / 1000 / 1000 + "\n"
+">>getInit(MB)=" + getInit / 1000 / 1000 + "\n"
+">>getUsed(MB)=" + getUsed / 1000 / 1000 + "\n"
+">>max(MB)=" + max / 1000 / 1000 + "\n";
} public static void main(String[] args){
System.out.println(new MemoryUseTest().getMemoryUseInfo());
}
} https://blog.csdn.net/dataiyangu/article/details/83539727
JVM中MemoryUsage中init,committed,used,max的含义
package java.lang.management;import javax.management.openmbean.CompositeData;import sun.management.MemoryUsageCompositeData;/**
* A <tt>MemoryUsage</tt> object represents a snapshot of memory usage.
* Instances of the <tt>MemoryUsage</tt> class are usually constructed
* by methods that are used to obtain memory usage
* information about individual memory pool of the Java virtual machine or
* the heap or non-heap memory of the Java virtual machine as a whole.
*
* <p> A <tt>MemoryUsage</tt> object contains four values:
* <table summary="Describes the MemoryUsage object content">
* <tr>
* <td valign=top> <tt>init</tt> </td>
* <td valign=top> represents the initial amount of memory (in bytes) that
* the Java virtual machine requests from the operating system
* for memory management during startup. The Java virtual machine
* may request additional memory from the operating system and
* may also release memory to the system over time.
* The value of <tt>init</tt> may be undefined.
* </td>
* </tr>
* <tr>
* <td valign=top> <tt>used</tt> </td>
* <td valign=top> represents the amount of memory currently used (in bytes).
* </td>
* </tr>
* <tr>
* <td valign=top> <tt>committed</tt> </td>
* <td valign=top> represents the amount of memory (in bytes) that is
* guaranteed to be available for use by the Java virtual machine.
* The amount of committed memory may change over time (increase
* or decrease). The Java virtual machine may release memory to
* the system and <tt>committed</tt> could be less than <tt>init</tt>.
* <tt>committed</tt> will always be greater than
* or equal to <tt>used</tt>.
* </td>
* </tr>
* <tr>
* <td valign=top> <tt>max</tt> </td>
* <td valign=top> represents the maximum amount of memory (in bytes)
* that can be used for memory management. Its value may be undefined.
* The maximum amount of memory may change over time if defined.
* The amount of used and committed memory will always be less than
* or equal to <tt>max</tt> if <tt>max</tt> is defined.
* A memory allocation may fail if it attempts to increase the
* used memory such that <tt>used > committed</tt> even
* if <tt>used <= max</tt> would still be true (for example,
* when the system is low on virtual memory).
* </td>
* </tr>
* </table>
*
* Below is a picture showing an example of a memory pool:
*
* <pre>
* +----------------------------------------------+
* +//////////////// | +
* +//////////////// | +
* +----------------------------------------------+
*
* |--------|
* init
* |---------------|
* used
* |---------------------------|
* committed
* |----------------------------------------------|
* max
* </pre>
*
* <h3>MXBean Mapping</h3>
* <tt>MemoryUsage</tt> is mapped to a {@link CompositeData CompositeData}
* with attributes as specified in the {@link #from from} method.
*
* @author Mandy Chung
* @since 1.5 */public class MemoryUsage { private final long init; private final long used; private final long committed; private final long max; /**
* Constructs a <tt>MemoryUsage</tt> object.
*
* @param init the initial amount of memory in bytes that
* the Java virtual machine allocates;
* or <tt>-1</tt> if undefined.
* @param used the amount of used memory in bytes.
* @param committed the amount of committed memory in bytes.
* @param max the maximum amount of memory in bytes that
* can be used; or <tt>-1</tt> if undefined.
*
* @throws IllegalArgumentException if
* <ul>
* <li> the value of <tt>init</tt> or <tt>max</tt> is negative
* but not <tt>-1</tt>; or</li>
* <li> the value of <tt>used</tt> or <tt>committed</tt> is negative;
* or</li>
* <li> <tt>used</tt> is greater than the value of <tt>committed</tt>;
* or</li>
* <li> <tt>committed</tt> is greater than the value of <tt>max</tt>
* <tt>max</tt> if defined.</li>
* </ul> */
public MemoryUsage(long init, long used, long committed, long max) { if (init < -1) { throw new IllegalArgumentException( "init parameter = " +
init + " is negative but not -1.");
} if (max < -1) { throw new IllegalArgumentException( "max parameter = " +
max + " is negative but not -1.");
} if (used < 0) { throw new IllegalArgumentException( "used parameter = " +
used + " is negative.");
} if (committed < 0) { throw new IllegalArgumentException( "committed parameter = " +
committed + " is negative.");
} if (used > committed) { throw new IllegalArgumentException( "used = " + used +
" should be <= committed = " + committed);
} if (max >= 0 && committed > max) { throw new IllegalArgumentException( "committed = " + committed +
" should be < max = " + max);
} this.init = init; this.used = used; this.committed = committed; this.max = max;
} /**
* Constructs a <tt>MemoryUsage</tt> object from a
* {@link CompositeData CompositeData}. */
private MemoryUsage(CompositeData cd) { // validate the input composite data MemoryUsageCompositeData.validateCompositeData(cd); this.init = MemoryUsageCompositeData.getInit(cd); this.used = MemoryUsageCompositeData.getUsed(cd); this.committed = MemoryUsageCompositeData.getCommitted(cd); this.max = MemoryUsageCompositeData.getMax(cd);
} /**
* Returns the amount of memory in bytes that the Java virtual machine
* initially requests from the operating system for memory management.
* This method returns <tt>-1</tt> if the initial memory size is undefined.
*
* @return the initial size of memory in bytes;
* <tt>-1</tt> if undefined. */
public long getInit() { return init;
} /**
* Returns the amount of used memory in bytes.
*
* @return the amount of used memory in bytes.
* */
public long getUsed() { return used;
}; /**
* Returns the amount of memory in bytes that is committed for
* the Java virtual machine to use. This amount of memory is
* guaranteed for the Java virtual machine to use.
*
* @return the amount of committed memory in bytes.
* */
public long getCommitted() { return committed;
}; /**
* Returns the maximum amount of memory in bytes that can be
* used for memory management. This method returns <tt>-1</tt>
* if the maximum memory size is undefined.
*
* <p> This amount of memory is not guaranteed to be available
* for memory management if it is greater than the amount of
* committed memory. The Java virtual machine may fail to allocate
* memory even if the amount of used memory does not exceed this
* maximum size.
*
* @return the maximum amount of memory in bytes;
* <tt>-1</tt> if undefined. */
public long getMax() { return max;
}; /**
* Returns a descriptive representation of this memory usage. */
public String toString() {
StringBuffer buf = new StringBuffer();
buf.append("init = " + init + "(" + (init >> 10) + "K) ");
buf.append("used = " + used + "(" + (used >> 10) + "K) ");
buf.append("committed = " + committed + "(" +
(committed >> 10) + "K) " );
buf.append("max = " + max + "(" + (max >> 10) + "K)"); return buf.toString();
} /**
* Returns a <tt>MemoryUsage</tt> object represented by the
* given <tt>CompositeData</tt>. The given <tt>CompositeData</tt>
* must contain the following attributes:
*
* <blockquote>
* <table border summary="The attributes and the types the given CompositeData contains">
* <tr>
* <th align=left>Attribute Name</th>
* <th align=left>Type</th>
* </tr>
* <tr>
* <td>init</td>
* <td><tt>java.lang.Long</tt></td>
* </tr>
* <tr>
* <td>used</td>
* <td><tt>java.lang.Long</tt></td>
* </tr>
* <tr>
* <td>committed</td>
* <td><tt>java.lang.Long</tt></td>
* </tr>
* <tr>
* <td>max</td>
* <td><tt>java.lang.Long</tt></td>
* </tr>
* </table>
* </blockquote>
*
* @param cd <tt>CompositeData</tt> representing a <tt>MemoryUsage</tt>
*
* @throws IllegalArgumentException if <tt>cd</tt> does not
* represent a <tt>MemoryUsage</tt> with the attributes described
* above.
*
* @return a <tt>MemoryUsage</tt> object represented by <tt>cd</tt>
* if <tt>cd</tt> is not <tt>null</tt>;
* <tt>null</tt> otherwise. */
public static MemoryUsage from(CompositeData cd) { if (cd == null) { return null;
} if (cd instanceof MemoryUsageCompositeData) { return ((MemoryUsageCompositeData) cd).getMemoryUsage();
} else { return new MemoryUsage(cd);
}
}
}
jdk 1.8.0_191
package com.taobao.arthas.core.command.monitor200;import com.alibaba.fastjson.JSON;import com.alibaba.fastjson.JSONObject;import com.taobao.arthas.core.command.Constants;import com.taobao.arthas.core.shell.command.AnnotatedCommand;import com.taobao.arthas.core.shell.command.CommandProcess;import com.taobao.arthas.core.shell.handlers.Handler;import com.taobao.arthas.core.shell.handlers.shell.QExitHandler;import com.taobao.arthas.core.shell.session.Session;import com.taobao.arthas.core.util.LogUtil;import com.taobao.arthas.core.util.NetUtils;import com.taobao.arthas.core.util.NetUtils.Response;import com.taobao.arthas.core.util.ThreadUtil;import com.taobao.arthas.core.util.metrics.SumRateCounter;import com.taobao.middleware.cli.annotations.Description;import com.taobao.middleware.cli.annotations.Name;import com.taobao.middleware.cli.annotations.Option;import com.taobao.middleware.cli.annotations.Summary;import com.taobao.middleware.logger.Logger;import com.taobao.text.Color;import com.taobao.text.Decoration;import com.taobao.text.Style;import com.taobao.text.renderers.ThreadRenderer;import com.taobao.text.ui.RowElement;import com.taobao.text.ui.TableElement;import com.taobao.text.util.RenderUtil;import java.lang.management.BufferPoolMXBean;import java.lang.management.GarbageCollectorMXBean;import java.lang.management.ManagementFactory;import java.lang.management.MemoryPoolMXBean;import java.lang.management.MemoryType;import java.lang.management.MemoryUsage;import java.util.List;import java.util.Map;import java.util.Timer;import java.util.TimerTask;/**
* @author hengyunabc 2015年11月19日 上午11:57:21 */@Name("dashboard")
@Summary("Overview of target jvm's thread, memory, gc, vm, tomcat info.")
@Description(Constants.EXAMPLE +
" dashboard\n" +
" dashboard -n 10\n" +
" dashboard -i 2000\n" +
Constants.WIKI + Constants.WIKI_HOME + "dashboard")public class DashboardCommand extends AnnotatedCommand { private static final Logger logger = LogUtil.getArthasLogger(); private SumRateCounter tomcatRequestCounter = new SumRateCounter(); private SumRateCounter tomcatErrorCounter = new SumRateCounter(); private SumRateCounter tomcatReceivedBytesCounter = new SumRateCounter(); private SumRateCounter tomcatSentBytesCounter = new SumRateCounter(); private int numOfExecutions = Integer.MAX_VALUE; private boolean batchMode; private long interval = 5000; private volatile long count = 0; private volatile Timer timer;
@Option(shortName = "n", longName = "number-of-execution")
@Description("The number of times this command will be executed.") public void setNumOfExecutions(int numOfExecutions) { this.numOfExecutions = numOfExecutions;
}
@Option(shortName = "b", longName = "batch")
@Description("Execute this command in batch mode.") public void setBatchMode(boolean batchMode) { this.batchMode = batchMode;
}
@Option(shortName = "i", longName = "interval")
@Description("The interval (in ms) between two executions, default is 5000 ms.") public void setInterval(long interval) { this.interval = interval;
}
@Override public void process(final CommandProcess process) {
Session session = process.session();
timer = new Timer("Timer-for-arthas-dashboard-" + session.getSessionId(), true); // ctrl-C support
process.interruptHandler(new DashboardInterruptHandler(process, timer)); /*
* 通过handle回调，在suspend和end时停止timer，resume时重启timer */
Handler<Void> stopHandler = new Handler<Void>() {
@Override public void handle(Void event) {
stop();
}
};
Handler<Void> restartHandler = new Handler<Void>() {
@Override public void handle(Void event) {
restart(process);
}
};
process.suspendHandler(stopHandler);
process.resumeHandler(restartHandler);
process.endHandler(stopHandler); // q exit support
process.stdinHandler(new QExitHandler(process)); // start the timer
timer.scheduleAtFixedRate(new DashboardTimerTask(process), 0, getInterval());
} public synchronized void stop() { if (timer != null) {
timer.cancel();
timer.purge();
timer = null;
}
} public synchronized void restart(CommandProcess process) { if (timer == null) {
Session session = process.session();
timer = new Timer("Timer-for-arthas-dashboard-" + session.getSessionId(), true);
timer.scheduleAtFixedRate(new DashboardTimerTask(process), 0, getInterval());
}
} public int getNumOfExecutions() { return numOfExecutions;
} public boolean isBatchMode() { return batchMode;
} public long getInterval() { return interval;
} private static String beautifyName(String name) { return name.replace(' ', '_').toLowerCase();
} private static void addBufferPoolMemoryInfo(TableElement table) { try {
@SuppressWarnings("rawtypes")
Class bufferPoolMXBeanClass = Class.forName("java.lang.management.BufferPoolMXBean");
@SuppressWarnings("unchecked")
List<BufferPoolMXBean> bufferPoolMXBeans = ManagementFactory.getPlatformMXBeans(bufferPoolMXBeanClass); for (BufferPoolMXBean mbean : bufferPoolMXBeans) { long used = mbean.getMemoryUsed(); long total = mbean.getTotalCapacity(); new MemoryEntry(mbean.getName(), used, total, Long.MIN_VALUE).addTableRow(table);
}
} catch (ClassNotFoundException e) { // ignore }
} private static void addRuntimeInfo(TableElement table) {
table.row("os.name", System.getProperty("os.name"));
table.row("os.version", System.getProperty("os.version"));
table.row("java.version", System.getProperty("java.version"));
table.row("java.home", System.getProperty("java.home"));
table.row("systemload.average",
String.format("%.2f", ManagementFactory.getOperatingSystemMXBean().getSystemLoadAverage()));
table.row("processors", "" + Runtime.getRuntime().availableProcessors());
table.row("uptime", "" + ManagementFactory.getRuntimeMXBean().getUptime() / 1000 + "s");
} private static void addMemoryInfo(TableElement table) {
MemoryUsage heapMemoryUsage = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();
MemoryUsage nonHeapMemoryUsage = ManagementFactory.getMemoryMXBean().getNonHeapMemoryUsage();
List<MemoryPoolMXBean> memoryPoolMXBeans = ManagementFactory.getMemoryPoolMXBeans(); new MemoryEntry("heap", heapMemoryUsage).addTableRow(table, Decoration.bold.bold()); for (MemoryPoolMXBean poolMXBean : memoryPoolMXBeans) { if (MemoryType.HEAP.equals(poolMXBean.getType())) {
MemoryUsage usage = poolMXBean.getUsage();
String poolName = beautifyName(poolMXBean.getName()); new MemoryEntry(poolName, usage).addTableRow(table);
}
} new MemoryEntry("nonheap", nonHeapMemoryUsage).addTableRow(table, Decoration.bold.bold()); for (MemoryPoolMXBean poolMXBean : memoryPoolMXBeans) { if (MemoryType.NON_HEAP.equals(poolMXBean.getType())) {
MemoryUsage usage = poolMXBean.getUsage();
String poolName = beautifyName(poolMXBean.getName()); new MemoryEntry(poolName, usage).addTableRow(table);
}
}
addBufferPoolMemoryInfo(table);
} private static void addGcInfo(TableElement table) {
List<GarbageCollectorMXBean> garbageCollectorMxBeans = ManagementFactory.getGarbageCollectorMXBeans(); for (GarbageCollectorMXBean garbageCollectorMXBean : garbageCollectorMxBeans) {
String name = garbageCollectorMXBean.getName();
table.add(new RowElement().style(Decoration.bold.bold()).add("gc." + beautifyName(name) + ".count", "" + garbageCollectorMXBean.getCollectionCount()));
table.row("gc." + beautifyName(name) + ".time(ms)", "" + garbageCollectorMXBean.getCollectionTime());
}
} private static String formatBytes(long size) { int unit = 1;
String unitStr = "B"; if (size / 1024 > 0) {
unit = 1024;
unitStr = "K";
} else if (size / 1024 / 1024 > 0) {
unit = 1024 * 1024;
unitStr = "M";
} return String.format("%d%s", size / unit, unitStr);
} private void addTomcatInfo(TableElement table) {
String threadPoolPath = "http://localhost:8006/connector/threadpool";
String connectorStatPath = "http://localhost:8006/connector/stats";
Response connectorStatResponse = NetUtils.request(connectorStatPath); if (connectorStatResponse.isSuccess()) {
List<JSONObject> connectorStats = JSON.parseArray(connectorStatResponse.getContent(), JSONObject.class); for (JSONObject stat : connectorStats) {
String name = stat.getString("name").replace("\"", ""); long bytesReceived = stat.getLongValue("bytesReceived"); long bytesSent = stat.getLongValue("bytesSent"); long processingTime = stat.getLongValue("processingTime"); long requestCount = stat.getLongValue("requestCount"); long errorCount = stat.getLongValue("errorCount");
tomcatRequestCounter.update(requestCount);
tomcatErrorCounter.update(errorCount);
tomcatReceivedBytesCounter.update(bytesReceived);
tomcatSentBytesCounter.update(bytesSent);
table.add(new RowElement().style(Decoration.bold.bold()).add("connector", name));
table.row("QPS", String.format("%.2f", tomcatRequestCounter.rate()));
table.row("RT(ms)", String.format("%.2f", processingTime / (double) requestCount));
table.row("error/s", String.format("%.2f", tomcatErrorCounter.rate()));
table.row("received/s", formatBytes((long) tomcatReceivedBytesCounter.rate()));
table.row("sent/s", formatBytes((long) tomcatSentBytesCounter.rate()));
}
}
Response threadPoolResponse = NetUtils.request(threadPoolPath); if (threadPoolResponse.isSuccess()) {
List<JSONObject> threadPoolInfos = JSON.parseArray(threadPoolResponse.getContent(), JSONObject.class); for (JSONObject info : threadPoolInfos) {
String name = info.getString("name").replace("\"", ""); long busy = info.getLongValue("threadBusy"); long total = info.getLongValue("threadCount");
table.add(new RowElement().style(Decoration.bold.bold()).add("threadpool", name));
table.row("busy", "" + busy);
table.row("total", "" + total);
}
}
} static String drawThreadInfo(int width, int height) {
Map<String, Thread> threads = ThreadUtil.getThreads(); return RenderUtil.render(threads.values().iterator(), new ThreadRenderer(), width, height);
} static String drawMemoryInfoAndGcInfo(int width, int height) {
TableElement table = new TableElement(1, 1);
TableElement memoryInfoTable = new TableElement(3, 1, 1, 1, 1).rightCellPadding(1);
memoryInfoTable.add(new RowElement().style(Decoration.bold.fg(Color.black).bg(Color.white)).add("Memory", "used", "total", "max", "usage"));
addMemoryInfo(memoryInfoTable);
TableElement gcInfoTable = new TableElement(1, 1).rightCellPadding(1);
gcInfoTable.add(new RowElement().style(Decoration.bold.fg(Color.black).bg(Color.white)).add("GC", ""));
addGcInfo(gcInfoTable);
table.row(memoryInfoTable, gcInfoTable); return RenderUtil.render(table, width, height);
}
String drawRuntineInfoAndTomcatInfo(int width, int height) {
TableElement table = new TableElement(1, 1);
TableElement runtimeInfoTable = new TableElement(1, 1).rightCellPadding(1);
runtimeInfoTable
.add(new RowElement().style(Decoration.bold.fg(Color.black).bg(Color.white)).add("Runtime", ""));
addRuntimeInfo(runtimeInfoTable);
TableElement tomcatInfoTable = new TableElement(1, 1).rightCellPadding(1); try { // 如果请求tomcat信息失败，则不显示tomcat信息
if (NetUtils.request("http://localhost:8006").isSuccess()) {
tomcatInfoTable
.add(new RowElement().style(Decoration.bold.fg(Color.black).bg(Color.white)).add("Tomcat", ""));
addTomcatInfo(tomcatInfoTable);
}
} catch (Throwable t) {
logger.error(null, "get Tomcat Info error!", t);
}
table.row(runtimeInfoTable, tomcatInfoTable); return RenderUtil.render(table, width, height);
} static class MemoryEntry {
String name; long used; long total; long max; int unit;
String unitStr; public MemoryEntry(String name, long used, long total, long max) { this.name = name; this.used = used; this.total = total; this.max = max;
unitStr = "K";
unit = 1024; if (used / 1024 / 1024 > 0) {
unitStr = "M";
unit = 1024 * 1024;
}
} public MemoryEntry(String name, MemoryUsage usage) {
this(name, usage.getUsed(), usage.getCommitted(), usage.getMax());
} private String format(long value) {
String valueStr = "-"; if (value == -1) { return "-1";
} if (value != Long.MIN_VALUE) {
valueStr = value / unit + unitStr;
} return valueStr;
} public void addTableRow(TableElement table) { double usage = used / (double) (max == -1 || max == Long.MIN_VALUE ? total : max) * 100;
table.row(name, format(used), format(total), format(max), String.format("%.2f%%", usage));
} public void addTableRow(TableElement table, Style.Composite style) { double usage = used / (double) (max == -1 || max == Long.MIN_VALUE ? total : max) * 100;
table.add(new RowElement().style(style).add(name, format(used), format(total), format(max),
String.format("%.2f%%", usage)));
}
} private class DashboardTimerTask extends TimerTask { private CommandProcess process; public DashboardTimerTask(CommandProcess process) { this.process = process;
}
@Override public void run() { if (count >= getNumOfExecutions()) { // stop the timer timer.cancel();
timer.purge();
process.write("Process ends after " + getNumOfExecutions() + " time(s).\n");
process.end(); return;
} int width = process.width(); int height = process.height(); // 上半部分放thread top。下半部分再切分为田字格，其中上面两格放memory, gc的信息。下面两格放tomcat, // runtime的信息
int totalHeight = height - 1; int threadTopHeight = totalHeight / 2; int lowerHalf = totalHeight - threadTopHeight; int runtimeInfoHeight = lowerHalf / 2; int heapInfoHeight = lowerHalf - runtimeInfoHeight;
String threadInfo = drawThreadInfo(width, threadTopHeight);
String memoryAndGc = drawMemoryInfoAndGcInfo(width, runtimeInfoHeight);
String runTimeAndTomcat = drawRuntineInfoAndTomcatInfo(width, heapInfoHeight);
process.write(threadInfo + memoryAndGc + runTimeAndTomcat);
count++;
process.times().incrementAndGet();
}
}
}
com.taobao.arthas.core.command.monitor200.DashboardCommand
