Java线程和多线程——Thread Dump

Posted EthanPark

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Java的Thread Dump就是列出JVM中所有激活状态的线程。

Java Thread Dump

Java Thread Dump在分析应用性能瓶颈和死锁的时候，是非常有效的。

下面将介绍多种不同的方式来获取Java程序的Thread Dump信息。这些指令在*nix型的操作系统下是有效的，但是在Windows下面，采取的方式会有一些不同。（主要是Pid信息获取不太一致，可通过任务管理器获取）

  1. VisualVM Profiler：如果开发者需要分析程序变慢的原因，那么必然要使用profiler。我们可以通过VisulaVM Profiler工具很容易的从运行的线程获取Thread Dump。你所需要的就是右键运行的进行，然后点击Thread Dump来获得这个信息。
  2. jstack：Java本身就自带的jstack工具，我们可以通过Java线程来直接生成Thread Dump。
    1. 受限找到Java进程的PID，可以通过ps -eaf | grep java命令来获取。
    2. 然后运行jstack工具，jstack PID来生成Thread Dump到控制台，当然，也可以通过重定向，将Thread Dump信息的输出通过命令jstack PID >> thread.dump写入thread.dump这个文本当中。

  3. 我们可以通过kill -3 PID命令来生成Thread Dump信息。这种方式和其它的生成Thread Dump的方式略有不同，当执行了kill命令的时候，Thread Dump信息会直接输出到控制台。所以，如果Java程序的System.out是控制台的话，Thread Dump的信息就会打印到控制台。如果Java的程序时一个Tomcat的服务程序，System.out将变成catalina.out文件，那时，Thread Dump会打印到catalina.out这个文件之中。
  4. Java 8引入了jcmd工具箱，开发者如果使用的是Java 8或者更高的版本的话，可以用之来替换掉jstack。命令行与jstack很类似：jcmd PID Thread.print。

上面的四种方式都可以用来在Java中生成Thread Dump的信息。通常，我推荐使用jstack或者jcmd命令来生成Thread Dump信息来分析。当然，无论你使用什么样的方式，最后的Thread Dump的信息都是一样的。

Java Thread Dump举例

我将自己写的一个Tomcat程序运行Thread Dump，结果如下：

$ jcmd 4428 Thread.print
4428:
2016-09-27 22:42:29
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.65-b01 mixed mode):

"ajp-nio-8009-AsyncTimeout" #39 daemon prio=5 os_prio=0 tid=0x000000001d4c4000 nid=0x34c4 waiting on condition [0x000000002ca1f000]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
        at java.lang.Thread.sleep(Native Method)
        at org.apache.coyote.AbstractProtocol$AsyncTimeout.run(AbstractProtocol.java:1080)
        at java.lang.Thread.run(Thread.java:745)

"ajp-nio-8009-Acceptor-0" #38 daemon prio=5 os_prio=0 tid=0x000000001d4c6800 nid=0x34c0 runnable [0x000000002c91f000]
   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 <0x0000000080b2bfb0> (a java.lang.Object)
        at org.apache.tomcat.util.net.NioEndpoint$Acceptor.run(NioEndpoint.java:508)
        at java.lang.Thread.run(Thread.java:745)

"ajp-nio-8009-ClientPoller-1" #37 daemon prio=5 os_prio=0 tid=0x000000001d4c3800 nid=0x34bc runnable [0x000000002c81e000]
   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 <0x00000000829ecd28> (a sun.nio.ch.Util$2)
        - locked <0x00000000829ecd18> (a java.util.Collections$UnmodifiableSet)
        - locked <0x00000000829ecba8> (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:843)
        at java.lang.Thread.run(Thread.java:745)

"ajp-nio-8009-ClientPoller-0" #36 daemon prio=5 os_prio=0 tid=0x000000001d4c5800 nid=0x34b8 runnable [0x000000002b72f000]
   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 <0x00000000829ee720> (a sun.nio.ch.Util$2)
        - locked <0x00000000829ee710> (a java.util.Collections$UnmodifiableSet)
        - locked <0x00000000829ee5a0> (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:843)
        at java.lang.Thread.run(Thread.java:745)

"http-nio-8080-AsyncTimeout" #35 daemon prio=5 os_prio=0 tid=0x000000001d4c1000 nid=0x34b4 waiting on condition [0x000000002b62f000]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
        at java.lang.Thread.sleep(Native Method)
        at org.apache.coyote.AbstractProtocol$AsyncTimeout.run(AbstractProtocol.java:1080)
        at java.lang.Thread.run(Thread.java:745)

"http-nio-8080-Acceptor-0" #34 daemon prio=5 os_prio=0 tid=0x000000001d4c2800 nid=0x34b0 runnable [0x000000002b52f000]
   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 <0x0000000080b30a30> (a java.lang.Object)
        at org.apache.tomcat.util.net.NioEndpoint$Acceptor.run(NioEndpoint.java:508)
        at java.lang.Thread.run(Thread.java:745)

"http-nio-8080-ClientPoller-1" #33 daemon prio=5 os_prio=0 tid=0x000000001d4c2000 nid=0x34ac runnable [0x000000002b1de000]
   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 <0x0000000082896118> (a sun.nio.ch.Util$2)
        - locked <0x0000000082896108> (a java.util.Collections$UnmodifiableSet)
        - locked <0x0000000082895f98> (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:843)
        at java.lang.Thread.run(Thread.java:745)

"http-nio-8080-ClientPoller-0" #32 daemon prio=5 os_prio=0 tid=0x000000001d4c0800 nid=0x34a8 runnable [0x000000002b0de000]
   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 <0x0000000082896af8> (a sun.nio.ch.Util$2)
        - locked <0x0000000082896ae8> (a java.util.Collections$UnmodifiableSet)
        - locked <0x0000000082896978> (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:843)
        at java.lang.Thread.run(Thread.java:745)

"ContainerBackgroundProcessor[StandardEngine[Catalina]]" #31 daemon prio=5 os_prio=0 tid=0x000000001f3d8800 nid=0x34a4 waiting on condition [0x0000000029fce000]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
        at java.lang.Thread.sleep(Native Method)
        at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1340)
        at java.lang.Thread.run(Thread.java:745)

"pool-2-thread-1" #30 prio=5 os_prio=0 tid=0x000000001f3dc800 nid=0x3498 waiting on condition [0x00000000288df000]
   java.lang.Thread.State: TIMED_WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x0000000082753eb0> (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:1067)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)

"Timer-0" #29 daemon prio=5 os_prio=0 tid=0x000000001f3d6000 nid=0x3494 in Object.wait() [0x000000002856f000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at java.util.TimerThread.mainLoop(Timer.java:552)
        - locked <0x0000000082751430> (a java.util.TaskQueue)
        at java.util.TimerThread.run(Timer.java:505)

"org.springframework.scheduling.quartz.SchedulerFactoryBean#0_QuartzSchedulerThread" #28 prio=5 os_prio=0 tid=0x000000001f3dd000 nid=0x3490 in Object.wait() [0x000000002846e000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at org.quartz.core.QuartzSchedulerThread.run(QuartzSchedulerThread.java:410)
        - locked <0x0000000082751b28> (a java.lang.Object)

"org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-10" #27 prio=5 os_prio=0 tid=0x000000001f3d7800 nid=0x348c in Object.wait() [0x000000002826f000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:568)
        - locked <0x0000000082717950> (a java.lang.Object)

"org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-9" #26 prio=5 os_prio=0 tid=0x000000001f3da000 nid=0x3488 in Object.wait() [0x000000002816f000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:568)
        - locked <0x0000000082717618> (a java.lang.Object)

"org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-8" #25 prio=5 os_prio=0 tid=0x000000001f3db800 nid=0x3484 in Object.wait() [0x000000002806f000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:568)
        - locked <0x00000000827172e0> (a java.lang.Object)

"org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-7" #24 prio=5 os_prio=0 tid=0x000000001f3d9000 nid=0x3480 in Object.wait() [0x0000000027f6f000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:568)
        - locked <0x0000000082716fa8> (a java.lang.Object)

"org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-6" #23 prio=5 os_prio=0 tid=0x000000001f3db000 nid=0x347c in Object.wait() [0x0000000027e6e000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:568)
        - locked <0x0000000082716c70> (a java.lang.Object)

"org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-5" #22 prio=5 os_prio=0 tid=0x000000001f3d7000 nid=0x3478 in Object.wait() [0x0000000027d6f000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:568)
        - locked <0x0000000082716938> (a java.lang.Object)

"org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-4" #21 prio=5 os_prio=0 tid=0x000000002107b800 nid=0x3474 in Object.wait() [0x0000000027c6f000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:568)
        - locked <0x0000000082716600> (a java.lang.Object)

"org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-3" #20 prio=5 os_prio=0 tid=0x0000000023019000 nid=0x3470 in Object.wait() [0x0000000027b6f000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:568)
        - locked <0x000000008270fb40> (a java.lang.Object)

"org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-2" #19 prio=5 os_prio=0 tid=0x000000001f6a4000 nid=0x346c in Object.wait() [0x000000002721f000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:568)
        - locked <0x00000000827162b0> (a java.lang.Object)

"org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-1" #18 prio=5 os_prio=0 tid=0x000000001a75a800 nid=0x3468 in Object.wait() [0x000000002014f000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:568)
        - locked <0x0000000082715f78> (a java.lang.Object)

"NioBlockingSelector.BlockPoller-2" #15 daemon prio=5 os_prio=0 tid=0x0000000019d0b000 nid=0x2150 runnable [0x000000001b59e000]
   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 <0x0000000080a8c5c8> (a sun.nio.ch.Util$2)
        - locked <0x0000000080a8c5b8> (a java.util.Collections$UnmodifiableSet)
        - locked <0x0000000080a8c448> (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:341)

"NioBlockingSelector.BlockPoller-1" #14 daemon prio=5 os_prio=0 tid=0x0000000019d09000 nid=0x890 runnable [0x000000001b49f000]
   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 <0x0000000080b2d2f8> (a sun.nio.ch.Util$2)
        - locked <0x0000000080b2d2e8> (a java.util.Collections$UnmodifiableSet)
        - locked <0x0000000080b2d188> (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:341)

"GC Daemon" #13 daemon prio=2 os_prio=-2 tid=0x0000000019e8d800 nid=0x27fc in Object.wait() [0x000000001b17f000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x0000000080c322d0> (a sun.misc.GC$LatencyLock)
        at sun.misc.GC$Daemon.run(GC.java:117)
        - locked <0x0000000080c322d0> (a sun.misc.GC$LatencyLock)

"Service Thread" #11 daemon prio=9 os_prio=0 tid=0x0000000018c19000 nid=0x2a78 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C1 CompilerThread2" #10 daemon prio=9 os_prio=2 tid=0x0000000018bc2800 nid=0x11b8 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread1" #9 daemon prio=9 os_prio=2 tid=0x0000000018bc1800 nid=0x1f90 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" #8 daemon prio=9 os_prio=2 tid=0x0000000018bbf800 nid=0x3288 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"JDWP Event Helper Thread" #7 daemon prio=10 os_prio=0 tid=0x0000000018bb2800 nid=0x339c runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"JDWP Transport Listener: dt_socket" #6 daemon prio=10 os_prio=0 tid=0x0000000018ba6800 nid=0x1628 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x00000000175cd800 nid=0x1790 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000000001761e000 nid=0xa24 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" #3 daemon prio=8 os_prio=1 tid=0x0000000002998000 nid=0xb94 in Object.wait() [0x000000001893f000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
        - locked <0x000000008051aa40> (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=0x000000000298f000 nid=0x5cc in Object.wait() [0x000000001883f000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at java.lang.Object.wait(Object.java:502)
        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:157)
        - locked <0x00000000800cce68> (a java.lang.ref.Reference$Lock)

"main" #1 prio=5 os_prio=0 tid=0x000000000240e000 nid=0x2478 runnable [0x000000000289e000]
   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 <0x0000000082a8afe0> (a java.net.SocksSocketImpl)
        at java.net.ServerSocket.implAccept(ServerSocket.java:545)
        at java.net.ServerSocket.accept(ServerSocket.java:513)
        at org.apache.catalina.core.StandardServer.await(StandardServer.java:446)
        at org.apache.catalina.startup.Catalina.await(Catalina.java:737)
        at org.apache.catalina.startup.Catalina.start(Catalina.java:683)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:497)
        at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:351)
        at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:485)

"VM Thread" os_prio=2 tid=0x0000000017587000 nid=0x1aec runnable

"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00000000028b7000 nid=0x1ea0 runnable

"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00000000028b8800 nid=0x19ac runnable

"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00000000028ba000 nid=0x2de8 runnable

"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00000000028bd000 nid=0x540 runnable

"VM Periodic Task Thread" os_prio=2 tid=0x0000000018c46000 nid=0x240c waiting on condition

JNI global references: 6164

Thread Dump会列出全部的线程，每个条目都包含如下的信息：

  1. Thread Name：线程的名字
  2. Thread Priority：线程的优先级
  3. Thread ID：代表线程的ID
  4. Thread Status：表示线程的状态，举例来说就是RUNNABLE，WAITING，BLOCKED等等，当在分析死锁的时候，可以查看阻塞的线程和被请求的资源。
  5. Thread CallStack：提供一个线程至关重要的堆栈信息。这也是我们可以看到线程获取的锁和是否在等待锁等信息。

通过上面这些信息，就能够看到一些程序的线程细节，当程序有一些问题之类，就可以从中找到真正影响性能的地方。

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如何使用thread dump和分析Thread dump？

[JAVA]JAVA章4 Thread Dump如何分析