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3步定位cpu占比过高或者oom

3步定位cpu占比过高或者oom

作者: b335eb9201c3 | 来源:发表于2020-02-14 18:13 被阅读0次

    jstack检测cpu高
    步骤一:查看cpu占用高进程

    top
    
    Mem:  16333644k total,  9472968k used,  6860676k free,   165616k buffers
    Swap:        0k total,        0k used,        0k free,  6665292k cached
    
      PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND     
    17850 root      20   0 7588m 112m  11m S 100.7  0.7  47:53.80 java       
     1552 root      20   0  121m  13m 8524 S  0.7  0.1  14:37.75 AliYunDun   
     3581 root      20   0 9750m 2.0g  13m S  0.7 12.9 298:30.20 java        
        1 root      20   0 19360 1612 1308 S  0.0  0.0   0:00.81 init        
        2 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kthreadd    
        3 root      RT   0     0    0    0 S  0.0  0.0   0:00.14 migration/0 
    

    步骤二:查看cpu占用高线程

    top -H -p 17850
    
    top - 17:43:15 up 5 days,  7:31,  1 user,  load average: 0.99, 0.97, 0.91
    Tasks:  32 total,   1 running,  31 sleeping,   0 stopped,   0 zombie
    Cpu(s):  3.7%us,  8.9%sy,  0.0%ni, 87.4%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
    Mem:  16333644k total,  9592504k used,  6741140k free,   165700k buffers
    Swap:        0k total,        0k used,        0k free,  6781620k cached
    
      PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
    17880 root      20   0 7588m 112m  11m R 99.9  0.7  50:47.43 java
    17856 root      20   0 7588m 112m  11m S  0.3  0.7   0:02.08 java
    17850 root      20   0 7588m 112m  11m S  0.0  0.7   0:00.00 java
    17851 root      20   0 7588m 112m  11m S  0.0  0.7   0:00.23 java
    17852 root      20   0 7588m 112m  11m S  0.0  0.7   0:02.09 java
    17853 root      20   0 7588m 112m  11m S  0.0  0.7   0:02.12 java
    17854 root      20   0 7588m 112m  11m S  0.0  0.7   0:02.07 java
    

    步骤三:转换线程ID

    printf "%x\n" 17880          
    45d8
    

    步骤四:定位cpu占用线程

    //jstack 17850(进程id)|grep 45d8(线程id,16进制) -A 30(显示前30行)
    jstack 17850|grep 45d8 -A 30
    
    "pool-1-thread-11" #20 prio=5 os_prio=0 tid=0x00007fc860352800 nid=0x45d8 runnable [0x00007fc8417d2000]
       java.lang.Thread.State: RUNNABLE
            at java.io.FileOutputStream.writeBytes(Native Method)
            at java.io.FileOutputStream.write(FileOutputStream.java:326)
            at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
            at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140)
            - locked <0x00000006c6c2e708> (a java.io.BufferedOutputStream)
            at java.io.PrintStream.write(PrintStream.java:482)
            - locked <0x00000006c6c10178> (a java.io.PrintStream)
            at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)
            at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:291)
            at sun.nio.cs.StreamEncoder.flushBuffer(StreamEncoder.java:104)
            - locked <0x00000006c6c26620> (a java.io.OutputStreamWriter)
            at java.io.OutputStreamWriter.flushBuffer(OutputStreamWriter.java:185)
            at java.io.PrintStream.write(PrintStream.java:527)
            - eliminated <0x00000006c6c10178> (a java.io.PrintStream)
            at java.io.PrintStream.print(PrintStream.java:597)
            at java.io.PrintStream.println(PrintStream.java:736)
            - locked <0x00000006c6c10178> (a java.io.PrintStream)
            at com.demo.guava.HardTask.call(HardTask.java:18)
            at com.demo.guava.HardTask.call(HardTask.java:9)
            at java.util.concurrent.FutureTask.run(FutureTask.java:266)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
            at java.lang.Thread.run(Thread.java:745)
    
    "pool-1-thread-10" #19 prio=5 os_prio=0 tid=0x00007fc860345000 nid=0x45d7 waiting on condition [0x00007fc8418d3000]
       java.lang.Thread.State: WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x00000006c6c14178> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
    

    jstack是java虚拟机自带的一种堆栈跟踪工具。

    jstack用于生成java虚拟机当前时刻的线程快照。线程快照是当前java虚拟机内每一条线程正在执行的方法堆栈的集合,生成线程快照的主要目的是定位线程出现长时间停顿的原因,

    如线程间死锁、死循环、请求外部资源导致的长时间等待等。 线程出现停顿的时候通过jstack来查看各个线程的调用堆栈,就可以知道没有响应的线程到底在后台做什么事情,或者

    等待什么资源。 如果java程序崩溃生成core文件,jstack工具可以用来获得core文件的java stack和native stack的信息,从而可以轻松地知道java程序是如何崩溃和在程

    序何处发生问题。另外,jstack工具还可以附属到正在运行的java程序中,看到当时运行的java程序的java stack和native stack的信息, 如果现在运行的java程序呈现hung

    的状态,jstack是非常有用的。

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