CPU高的排查

时间 2019-11-06

标签 cpu 高的排查繁體版

原文原文链接

以前有朋友反馈说发的内容但愿有个梯度，逐步加深，前面发了几篇关于jvm源码分析的文章，可能我以为我已经把内容写得浅显易懂了，可是对于某些没怎么接触的同窗来讲仍是比较难理解，这个我之后慢慢改进吧，今天发篇轻松点的文章，可能你们在工做过程当中也会可能碰到相似的问题，或许有经验的同窗看到这个题目就知道我要说什么了，也有本身的定位方法。java

话很少说了，先来看代码吧web

public class Test{jvm

public static void main(String args[]){源码分析

for(int i=0;i<10;i++){spa

new Thread(){线程

public void run(){进程

try{源码

Thread.sleep(100000);it

}catch(Exception e){}io

}

}.start();

}

Thread t=new Thread(){

public void run(){

int i=0;

while(true){

i=(i++)/100;

}

};

t.setName("Busiest Thread");

t.start();

}

这个例子里新建立了11个线程，其中10个线程没干什么事，主要是sleep，另外有一个线程在循环里一直跑着，能够想象这个线程是这个进程里最耗cpu的线程了，那怎么把这个线程给抓出来呢？

首先咱们能够经过top -Hp <pid>来看这个进程里全部线程的cpu消耗状况，获得相似下面的数据

$ top -Hp 18207

top - 19:11:43 up 573 days, 2:43, 2 users, load average: 3.03, 3.03, 3.02

Tasks: 44 total, 1 running, 43 sleeping, 0 stopped, 0 zombie

Cpu(s): 18.8%us, 0.0%sy, 0.0%ni, 81.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st

Mem: 99191752k total, 98683576k used, 508176k free, 128248k buffers

Swap: 1999864k total, 191064k used, 1808800k free, 17413760k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND

18250 admin 20 0 26.1g 28m 10m R 99.9 0.0 0:19.50 java Test

18207 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18208 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.09 java Test

18209 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18210 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18211 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18212 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18213 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18214 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18215 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18216 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18217 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18218 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18219 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18220 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18221 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18222 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18223 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18224 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18225 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18226 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

18227 admin 20 0 26.1g 28m 10m S 0.0 0.0 0:00.00 java Test

拿到这个结果以后，咱们能够看到cpu最高的线程是pid为18250的线程，占了99.8%：

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND

18250 admin 20 0 26.1g 28m 10m R 99.9 0.0 0:19.50 java Test

接着咱们能够经过jstack <pid>的输出来看各个线程栈:

$ jstack 18207

2016-03-30 19:12:23

Full thread dump OpenJDK 64-Bit Server VM (25.66-b60 mixed mode):

"Attach Listener" #30 daemon prio=9 os_prio=0 tid=0x00007fb90be13000 nid=0x47d7 waiting on condition [0x0000000000000000]

java.lang.Thread.State: RUNNABLE

"DestroyJavaVM" #29 prio=5 os_prio=0 tid=0x00007fb96245b800 nid=0x4720 waiting on condition [0x0000000000000000]

java.lang.Thread.State: RUNNABLE

"Busiest Thread" #28 prio=5 os_prio=0 tid=0x00007fb91498d000 nid=0x474a runnable [0x00007fb9065fe000]

java.lang.Thread.State: RUNNABLE

at Test$2.run(Test.java:18)

"Thread-9" #27 prio=5 os_prio=0 tid=0x00007fb91498c800 nid=0x4749 waiting on condition [0x00007fb906bfe000]

java.lang.Thread.State: TIMED_WAITING (sleeping)

at java.lang.Thread.sleep(Native Method)

at Test$1.run(Test.java:9)

"Thread-8" #26 prio=5 os_prio=0 tid=0x00007fb91498b800 nid=0x4748 waiting on condition [0x00007fb906ffe000]

java.lang.Thread.State: TIMED_WAITING (sleeping)

at java.lang.Thread.sleep(Native Method)

at Test$1.run(Test.java:9)

"Thread-7" #25 prio=5 os_prio=0 tid=0x00007fb91498b000 nid=0x4747 waiting on condition [0x00007fb9073fe000]

java.lang.Thread.State: TIMED_WAITING (sleeping)

at java.lang.Thread.sleep(Native Method)

at Test$1.run(Test.java:9)

"Thread-6" #24 prio=5 os_prio=0 tid=0x00007fb91498a000 nid=0x4746 waiting on condition [0x00007fb9077fe000]

java.lang.Thread.State: TIMED_WAITING (sleeping)

at java.lang.Thread.sleep(Native Method)

at Test$1.run(Test.java:9)

...

上面的线程栈咱们注意到nid的值其实就是线程ID，它是十六进制的，咱们将消耗cpu最高的线程18250，转成十六进制0X47A，而后从上面的线程栈里找到nid=0X47A的线程，其栈为：

"Busiest Thread" #28 prio=5 os_prio=0 tid=0x00007fb91498d000 nid=0x474a runnable [0x00007fb9065fe000]

java.lang.Thread.State: RUNNABLE

at Test$2.run(Test.java:18)

即将最耗cpu的线程找出来了，是Businest Thread