CPU高的排查

時間 2019-11-06

標籤 cpu 高的排查简体版

原文原文鏈接

以前有朋友反饋說發的內容但願有個梯度，逐步加深，前面發了幾篇關於jvm源碼分析的文章，可能我以爲我已經把內容寫得淺顯易懂了，可是對於某些沒怎麼接觸的同窗來講仍是比較難理解，這個我之後慢慢改進吧，今天發篇輕鬆點的文章，可能你們在工做過程當中也會可能碰到相似的問題，或許有經驗的同窗看到這個題目就知道我要說什麼了，也有本身的定位方法。java

話很少說了，先來看代碼吧web

public class Test{jvm

public static void main(String args[]){源碼分析

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

new Thread(){線程

public void run(){進程

try{源碼

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();

}

這個例子裏新建立了11個線程，其中10個線程沒幹什麼事，主要是sleep，另外有一個線程在循環裏一直跑着，能夠想象這個線程是這個進程裏最耗cpu的線程了，那怎麼把這個線程給抓出來呢？

首先咱們能夠經過top -Hp <pid>來看這個進程裏全部線程的cpu消耗狀況，獲得相似下面的數據

$ 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

拿到這個結果以後，咱們能夠看到cpu最高的線程是pid爲18250的線程，佔了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

接着咱們能夠經過jstack <pid>的輸出來看各個線程棧:

$ 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)

...

上面的線程棧咱們注意到nid的值其實就是線程ID，它是十六進制的，咱們將消耗cpu最高的線程18250，轉成十六進制0X47A，而後從上面的線程棧裏找到nid=0X47A的線程，其棧爲：

"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)

即將最耗cpu的線程找出來了，是Businest Thread

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