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JVM参数类型

标准参数

• -help
• -server -client
• -version -showversion
• -cp -classpath

X参数

• -Xint 解释执行
• -Xcomp 第一次执行使用就编译成本地代码 （interpret）
• -Xmixed 混合模式，JVM自己决定是否编译成本地代码（compile）
  

XX参数

Boolean类型

• 格式：-XX：[+-] <name> 表示启动或者禁用name属性
• 例如：
  • -XX:+UserConcMarkSweepGC 启用CMS垃圾收集器
  • -XX:+UseG1GC 启用G1垃圾收集器

非Boolean类型

• 格式：-XX:<name>=<value> 表示name属性的值是vlaue
• 例如：
  • -XX:MaxGCPauseMillis=500 表示GC最大停顿时间500ms
  • -XX:GCTimeRatio=19

-Xmx -Xms 不是X参数，而是XX参数

-Xms 等价于 -XX:InitialHeapSize

-Xmx 等价于 -XX:MaxHeapSize

jinfo查看JVM运行参数

• -XX：+PrintFlagsInitial
• -XX：+PrintFlagsFinal
• -XX：UnlockExperimentalVMOptions 解锁实验参数
• -XX：+UnlockDiagnosticVMOptions 解锁诊断参数
• -XX：+PrintCommandLineFlags 打印命令行参数

【命令格式】

• 查看最大内存：jinfo -flag MaxHeapSize <pid>
  
• 查看垃圾回收器：jinfo -flag <GC> <pid>
  • jinfo -flag UseConcMarkSweepGC 2444
    
  • jinfo -flag UseG1GC 2444
  • jinfo -flag UseParallelGC 2444

jstat查看JVM统计信息

【命令格式】

• -class ：jstat -class 2444 1000 10

  
  查看已加载类和卸载类的个数和大小，以及加载和卸载花费的时间

• -gc：jstat -gc 2444 1000 3

  
  
  S0U、S1C、S0U、S1U：S0和S1的总量和使用量（Capacity，Utilization）
  EC、EU：Eden区总量和使用量
  OC、OU：Old区总量和使用量
  MC、MU：Metaspace区总量和使用量
  CCSC、CCSU：压缩类空间总量和使用量
  YGC、YGCT：YoungGC次数与时间
  FGC、FGCT：FullGC次数与时间
  GCT：总GC时间

• -compile：jstat -compiler 2444

  

jmap 分析内存溢出

演示内存溢出

@RestControllerpublic class MemoryController {
       private List
   
     userList = new ArrayList<>();    private List
    
     > classList = new ArrayList<>();    //-Xmx32M -Xms32M    // heap溢出    @GetMapping("/heap")    public String heap(){
           int i = 0;        while (true){
               userList.add(new User(i++, UUID.randomUUID().toString()));        }    }    //-XX:MetaspaceSize=32M -XX:MetaspaceSize=32M    // metaspace溢出    @GetMapping("/nonheap")    public String nonHeap(){
           int i = 0;        while (true){
           	// 使用ASM工具生成字节码文件	            classList.addAll(MetaSpace.createClasses());        }    }}
    
   

heap溢出：

导出内存映像文件

• 内存溢出自动导出

  • -XX:+HeapDumpOnOutOfMemoryError
  • -XX:HeapDumpPath=./

• jmap手动导出

  
  • jmap -dump:format=b,file=heap.bin 15988
    
  • jmap -heap 15988
    

jstack查看线程状态

jstack 1388

C:\Users\where\Desktop>jstack 13882019-08-11 22:22:44Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.152-b16 mixed mode):"DestroyJavaVM" #41 prio=5 os_prio=0 tid=0x000000001876c800 nid=0x238c waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"http-nio-8080-Acceptor" #39 daemon prio=5 os_prio=0 tid=0x000000001876a000 nid=0xb6c runnable [0x000000001a98f000]   java.lang.Thread.State: RUNNABLE        at sun.nio.ch.ServerSocketChannelImpl.accept0(Native Method)        at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:422)        at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:250)        - locked <0x00000000ff76a6e8> (a java.lang.Object)        at org.apache.tomcat.util.net.NioEndpoint.serverSocketAccept(NioEndpoint.java:463)        at org.apache.tomcat.util.net.NioEndpoint.serverSocketAccept(NioEndpoint.java:73)        at org.apache.tomcat.util.net.Acceptor.run(Acceptor.java:95)        at java.lang.Thread.run(Thread.java:748)"http-nio-8080-ClientPoller" #38 daemon prio=5 os_prio=0 tid=0x0000000018771000 nid=0x31d8 runnable [0x000000001a88e000]   java.lang.Thread.State: RUNNABLE        at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)        at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296)        at sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278)        at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159)        at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)        - locked <0x00000000ff8454f0> (a sun.nio.ch.Util$3)        - locked <0x00000000ff8454e0> (a java.util.Collections$UnmodifiableSet)        - locked <0x00000000ff845390> (a sun.nio.ch.WindowsSelectorImpl)        at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)        at org.apache.tomcat.util.net.NioEndpoint$Poller.run(NioEndpoint.java:708)        at java.lang.Thread.run(Thread.java:748)"http-nio-8080-exec-1" #28 daemon prio=5 os_prio=0 tid=0x000000001875f800 nid=0x1980 waiting on condition [0x0000000019e8e000]   java.lang.Thread.State: WAITING (parking)        at sun.misc.Unsafe.park(Native Method)        - parking to wait for  <0x00000000ff81af68> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)        at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)        at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:107)        at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)        at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)        at java.lang.Thread.run(Thread.java:748)"http-nio-8080-BlockPoller" #27 daemon prio=5 os_prio=0 tid=0x000000001875e000 nid=0x3c5c runnable [0x0000000019d8e000]   java.lang.Thread.State: RUNNABLE        at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)        at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296)        at sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278)        at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159)        at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)        - locked <0x00000000ff775c70> (a sun.nio.ch.Util$3)        - locked <0x00000000ff7753d8> (a java.util.Collections$UnmodifiableSet)        - locked <0x00000000ff775220> (a sun.nio.ch.WindowsSelectorImpl)        at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)        at org.apache.tomcat.util.net.NioBlockingSelector$BlockPoller.run(NioBlockingSelector.java:313)"container-0" #26 prio=5 os_prio=0 tid=0x00000000186a1800 nid=0x14c4 waiting on condition [0x0000000019a8f000]   java.lang.Thread.State: TIMED_WAITING (sleeping)        at java.lang.Thread.sleep(Native Method)        at org.apache.catalina.core.StandardServer.await(StandardServer.java:570)        at org.springframework.boot.web.embedded.tomcat.TomcatWebServer$1.run(TomcatWebServer.java:179)"Catalina-utility-1" #24 prio=1 os_prio=-2 tid=0x00000000186be000 nid=0x3dcc waiting on condition [0x000000001988e000]   java.lang.Thread.State: TIMED_WAITING (parking)        at sun.misc.Unsafe.park(Native Method)        - parking to wait for  <0x00000000fee26350> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)        at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)        at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1093)        at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)        at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)        at java.lang.Thread.run(Thread.java:748)"RMI Scheduler(0)" #18 daemon prio=5 os_prio=0 tid=0x0000000016701800 nid=0x1d6c waiting on condition [0x00000000177bf000]   java.lang.Thread.State: TIMED_WAITING (parking)        at sun.misc.Unsafe.park(Native Method)        - parking to wait for  <0x00000000fe051338> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)        at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)        at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1093)        at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)        at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)        at java.lang.Thread.run(Thread.java:748)"RMI TCP Accept-61297" #14 daemon prio=5 os_prio=0 tid=0x000000001649e800 nid=0x2f6c runnable [0x0000000016d0e000]   java.lang.Thread.State: RUNNABLE        at java.net.DualStackPlainSocketImpl.accept0(Native Method)        at java.net.DualStackPlainSocketImpl.socketAccept(DualStackPlainSocketImpl.java:131)        at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409)        at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:199)        - locked <0x00000000fe641650> (a java.net.SocksSocketImpl)        at java.net.ServerSocket.implAccept(ServerSocket.java:545)        at java.net.ServerSocket.accept(ServerSocket.java:513)        at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(TCPTransport.java:400)        at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(TCPTransport.java:372)        at java.lang.Thread.run(Thread.java:748)"RMI TCP Accept-0" #13 daemon prio=5 os_prio=0 tid=0x0000000016486000 nid=0x208c runnable [0x0000000016c0f000]   java.lang.Thread.State: RUNNABLE        at java.net.DualStackPlainSocketImpl.accept0(Native Method)        at java.net.DualStackPlainSocketImpl.socketAccept(DualStackPlainSocketImpl.java:131)        at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409)        at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:199)        - locked <0x00000000fe641af8> (a java.net.SocksSocketImpl)        at java.net.ServerSocket.implAccept(ServerSocket.java:545)        at java.net.ServerSocket.accept(ServerSocket.java:513)        at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(TCPTransport.java:400)        at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(TCPTransport.java:372)        at java.lang.Thread.run(Thread.java:748)"Service Thread" #11 daemon prio=9 os_prio=0 tid=0x0000000015966800 nid=0xf58 runnable [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"C1 CompilerThread3" #10 daemon prio=9 os_prio=2 tid=0x00000000158c7800 nid=0x33d0 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"C2 CompilerThread2" #9 daemon prio=9 os_prio=2 tid=0x00000000158c5000 nid=0xcc8 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"C2 CompilerThread1" #8 daemon prio=9 os_prio=2 tid=0x00000000158c4000 nid=0x305c waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"C2 CompilerThread0" #7 daemon prio=9 os_prio=2 tid=0x00000000158a6000 nid=0x2194 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"Monitor Ctrl-Break" #6 daemon prio=5 os_prio=0 tid=0x00000000158b7000 nid=0x53c runnable [0x0000000015e0f000]   java.lang.Thread.State: RUNNABLE        at java.net.SocketInputStream.socketRead0(Native Method)        at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)        at java.net.SocketInputStream.read(SocketInputStream.java:171)        at java.net.SocketInputStream.read(SocketInputStream.java:141)        at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)        at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)        at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)        - locked <0x00000000fe399b50> (a java.io.InputStreamReader)        at java.io.InputStreamReader.read(InputStreamReader.java:184)        at java.io.BufferedReader.fill(BufferedReader.java:161)        at java.io.BufferedReader.readLine(BufferedReader.java:324)        - locked <0x00000000fe399b50> (a java.io.InputStreamReader)        at java.io.BufferedReader.readLine(BufferedReader.java:389)        at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:64)"Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x00000000156a2800 nid=0x940 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000000001564d000 nid=0x3be4 runnable [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"Finalizer" #3 daemon prio=8 os_prio=1 tid=0x0000000013743800 nid=0x9e8 in Object.wait() [0x0000000015b0e000]   java.lang.Thread.State: WAITING (on object monitor)        at java.lang.Object.wait(Native Method)        - waiting on <0x00000000fe63aef0> (a java.lang.ref.ReferenceQueue$Lock)        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)        - locked <0x00000000fe63aef0> (a java.lang.ref.ReferenceQueue$Lock)        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)"Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x0000000003089800 nid=0x3d38 in Object.wait() [0x000000001560e000]   java.lang.Thread.State: WAITING (on object monitor)        at java.lang.Object.wait(Native Method)        - waiting on <0x00000000fe399bf8> (a java.lang.ref.Reference$Lock)        at java.lang.Object.wait(Object.java:502)        at java.lang.ref.Reference.tryHandlePending(Reference.java:191)        - locked <0x00000000fe399bf8> (a java.lang.ref.Reference$Lock)        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)"VM Thread" os_prio=2 tid=0x0000000013738000 nid=0xf8 runnable"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x0000000002fab000 nid=0x1614 runnable"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x0000000002fad000 nid=0x29e8 runnable"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x0000000002fae800 nid=0x3a74 runnable"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x0000000002fb0000 nid=0x910 runnable"GC task thread#4 (ParallelGC)" os_prio=0 tid=0x0000000002fb2000 nid=0x3fe8 runnable"GC task thread#5 (ParallelGC)" os_prio=0 tid=0x0000000002fb4800 nid=0x134c runnable"GC task thread#6 (ParallelGC)" os_prio=0 tid=0x0000000002fb7800 nid=0x3890 runnable"GC task thread#7 (ParallelGC)" os_prio=0 tid=0x0000000002fb8800 nid=0x3a8 runnable"VM Periodic Task Thread" os_prio=2 tid=0x00000000164ae000 nid=0x748 waiting on conditionJNI global references: 1034

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