Dump文件分析(转发)

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原文:

Dump文件分析

 

本文主要介绍Dump文件结构,理解Dump文件对于分析线程高占用、死锁、内存溢出等高级问题有非常重要的指导意义。

什么是Dump文件

Dump文件是进程的内存镜像。可以把程序的执行状态通过调试器保存到dump文件中。
Dump文件是用来给程序编写人员调试程序用的,这种文件必须用专用工具软件打开

如何生成Dump文件

使用命令:jstack pid
可以查看到当前运行的java进程的dump信息。

Dump文件结构

首先浏览一下dump文件的文本内容:

Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.77-b03 mixed mode): "Attach Listener" #37 daemon prio=9 os_prio=0 tid=0x00007f87b42b7000 nid=0x680f waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Druid-ConnectionPool-Destory-331358539" #36 daemon prio=5 os_prio=0 tid=0x00007f87a4278800 nid=0x67e4 waiting on condition [0x00007f87b8dce000] java.lang.Thread.State: TIMED_WAITING (sleeping) at java.lang.Thread.sleep(Native Method) at com.alibaba.druid.pool.DruidDataSource$DestroyConnectionThread.run(DruidDataSource.java:1724) "Druid-ConnectionPool-Create-331358539" #35 daemon prio=5 os_prio=0 tid=0x00007f87a4022000 nid=0x67e3 waiting on condition [0x00007f87ce86a000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000000b3804848> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:1629) "Abandoned connection cleanup thread" #31 daemon prio=5 os_prio=0 tid=0x00007f87e0d91800 nid=0x672b in Object.wait() [0x00007f87cd2c2000] java.lang.Thread.State: TIMED_WAITING (on object monitor) at java.lang.Object.wait(Native Method) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143) - locked <0x00000000b422d1e8> (a java.lang.ref.ReferenceQueue$Lock) at com.mysql.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:43) "DestroyJavaVM" #30 prio=5 os_prio=0 tid=0x00007f87e0008800 nid=0x670b waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "http-nio-8081-AsyncTimeout" #28 daemon prio=5 os_prio=0 tid=0x00007f87e016e800 nid=0x6727 waiting on condition [0x00007f87b94cf000] java.lang.Thread.State: TIMED_WAITING (sleeping) at java.lang.Thread.sleep(Native Method) at org.apache.coyote.AbstractProtocol$AsyncTimeout.run(AbstractProtocol.java:1211) at java.lang.Thread.run(Thread.java:745) "http-nio-8081-Acceptor-0" #27 daemon prio=5 os_prio=0 tid=0x00007f87e0166000 nid=0x6726 runnable [0x00007f87b95d0000] 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 <0x00000000b410d480> (a java.lang.Object) at org.apache.tomcat.util.net.NioEndpoint$Acceptor.run(NioEndpoint.java:455) at java.lang.Thread.run(Thread.java:745) "http-nio-8081-ClientPoller-0" #26 daemon prio=5 os_prio=0 tid=0x00007f87e0292800 nid=0x6725 runnable [0x00007f87b96d1000] java.lang.Thread.State: RUNNABLE at sun.nio.ch.EPollArrayWrapper.epollWait(Native Method) at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:269) at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:93) at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86) - locked <0x00000000b410d6c0> (a sun.nio.ch.Util$2) - locked <0x00000000b410d6b0> (a java.util.Collections$UnmodifiableSet) - locked <0x00000000b410d668> (a sun.nio.ch.EPollSelectorImpl) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97) at org.apache.tomcat.util.net.NioEndpoint$Poller.run(NioEndpoint.java:793) at java.lang.Thread.run(Thread.java:745) "http-nio-8081-exec-10" #25 daemon prio=5 os_prio=0 tid=0x00007f87e028c000 nid=0x6724 waiting on condition [0x00007f87b97d2000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000000b410d898> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745)

其中每个空行用于分隔一个线程,每个线程的信息是以堆栈信息的方式展开,显示了目前正在调用的方法以及所在的代码行。每个线程信息的第一行是描述该线程的基本信息,例如:

"http-nio-8081-exec-10" #25 daemon prio=5 os_prio=0 tid=0x00007f87e028c000 nid=0x6724 waiting on condition [0x00007f87b97d2000]

 

每一个部分的含义如下:

  • “http-nio-8081-exec-10” 线程名称
  • #25 线程编号
  • daemon 线程的类型
  • prio=5 线程的优先级别
  • os_prio=0 系统级别的线程优先级
  • tid=0x00007f87e028c000 线程ID
  • nid=0x6724 native线程的id
  • waiting on condition [0x00007f87b97d2000] 线程当前的状态

线程当前的状态是我们主要关注的内容。

dump文件中描述的线程状态

runnable:运行中状态,在虚拟机内部执行,可能已经获取到了锁,可以观察是否有locked字样。
blocked:被阻塞并等待锁的释放。
wating:处于等待状态,等待特定的操作被唤醒,一般停留在park(), wait(), sleep(),join() 等语句里。
time_wating:有时限的等待另一个线程的特定操作。
terminated:线程已经退出。

进程区域的划分

技术图片

 

 

进入区(Entry Set):等待获取对象锁,一旦对象锁释放,立即参与竞争。
拥有区(The Owner):已经获取到锁。
等待区(Wait Set):表示线程通过wait方法释放了对象锁,并在等待区等待被唤醒。

方法调用修饰

locked: 成功获取锁
waiting to lock:还未获取到锁,在进入去等待;
waiting on:获取到锁之后,又释放锁,在等待区等待;
parking to wait for:等待许可证; (参考LockSupport.park和unpark操作)

结尾

有了这些知识之后我们再看前面的Dump文件就非常清楚了,清楚的描述了线程当前所处的状态以及获取到的锁的信息,例如:

"http-nio-8081-exec-2" #17 daemon prio=5 os_prio=0 tid=0x00007f87e0685800 nid=0x671c waiting on condition [0x00007f87cc5bd000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000000b410d898> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)

 

名称为‘http-nio-8081-exec-2’的线程当前正处于等待状态,等待其他线程释放许可证。(请先了解LockSupport的park和unpark操作)

"http-nio-8081-AsyncTimeout" #28 daemon prio=5 os_prio=0 tid=0x00007f87e016e800 nid=0x6727 waiting on condition [0x00007f87b94cf000] java.lang.Thread.State: TIMED_WAITING (sleeping) at java.lang.Thread.sleep(Native Method)

 

名称为‘http-nio-8081-AsyncTimeout’的线程当前处于等待状态,经过一个特定的休眠时间之后将自动唤醒。

综上所述,dump文件结构还是比较简单的,这对于我们分析线程的执行情况非常有用,是每一个Java程序员必须掌握的高级技能之一。

Dump文件分析(转发)

标签:reference   abstract   uid   data   str   比较   ping   queue   log   

原文地址:https://www.cnblogs.com/panpanwelcome/p/14294392.html

版权声明:完美者 发表于 2021-01-19 12:10:17。
转载请注明:Dump文件分析(转发) | 完美导航

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