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Java Thread Dump Supporting tagline

jstack

Thread Dump信息

Thread Run States

jstack

Usage:

jstack [-l] <pid>
    (to connect to running process)
jstack -F [-m] [-l] <pid>
    (to connect to a hung process)
jstack [-m] [-l] <executable> <core>
    (to connect to a core file)
jstack [-m] [-l] [server_id@]<remote server IP or hostname>
    (to connect to a remote debug server)

Options:

-F  to force a thread dump. Use when jstack <pid> does not respond (process is hung)
-m  to print both java and native frames (mixed mode)
-l  long listing. Prints additional information about locks
-h or -help to print this help message
  1. 1 首先介绍一下Thread Dump信息的各个部分

Thread Dump信息

头部信息：

时间，jvm信息
2011-11-02 19:05:06  
Full thread dump Java HotSpot(TM) Server VM (16.3-b01 mixed mode):

线程info信息块：

1. "Timer-0" daemon prio=10tid=0xac190c00 nid=0xaef in Object.wait() [0xae77d000]
2.  java.lang.Thread.State: TIMED_WAITING (on object monitor)
3.  atjava.lang.Object.wait(Native Method)
4.  -waiting on <0xb3885f60> (a java.util.TaskQueue)     ###继续wait 
5.  atjava.util.TimerThread.mainLoop(Timer.java:509)
6.  -locked <0xb3885f60> (a java.util.TaskQueue)         ###已经locked
7.  atjava.util.TimerThread.run(Timer.java:462)

* 线程名称：Timer-0
* 线程类型：daemon
* 优先级: 10，默认是5
* jvm线程id：tid=0xac190c00，jvm内部线程的唯一标识（通过java.lang.Thread.getId()获取，通常用自增方式实现。）
* 对应系统线程id（NativeThread ID）：nid=0xaef，和top命令查看的线程pid对应，不过一个是10进制，一个是16进制。（通过命令：top -H -p pid，可以查看该进程的所有线程信息）
* 线程状态：in Object.wait().
* 起始栈地址：[0xae77d000]
* Java thread statck trace：是上面2-7行的信息。到目前为止这是最重要的数据，Java stack trace提供了大部分信息来精确定位问题根源。

Thread Run States

State Description

blocked

This thread tried to enter a synchronized block, but the lock was taken by another thread. This thread is blocked until the lock gets released.

blocked (on thin lock)

This is the same state as blocked, but the lock in question is a thin lock.

waiting

This thread called Object.wait() on an object. The thread will remain there until some other thread sends a notification to that object.

sleeping

This thread called java.lang.Thread.sleep().

parked

This thread called java.util.concurrent.locks.LockSupport.park().

suspended

The thread's execution was suspended by java.lang.Thread.suspend() or a JVMTI agent call.

查找占用cpu最多的线程信息

方案：
java dump thread：
	jstack -l pid
找到导致cpu高的线程:
	top -H -p pid，对应的线程id是十进制的
十进制转十六进制，对应dump中nid(NativeThread ID)
从dump中找到对应的线程

参考资料

Using Thread Dumps(oracle doc)

性能分析之– JAVA Thread Dump 分析综述

thread dump分析

Published

27 November 2013

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