Java影响CPU增高的原因,分析java程序cpu占用较高原因过程

1.Java程序import java.io.Serializable;

public class Test {

public static void main(String[] args) throws InterruptedException {

while (true){ //一直循环创建User对象

User user = new User();

user.userName1 = "username1";

user.userName2 = "userName2";

user.userName3 = "userName3";

user.userName4 = "userName4";

user.userName5 = "userName5";

user.userName6 = "userName6";

user.userName7 = "userName7";

user.userName8 = "userName8";

}

}

public static void service(){

return;

}

public static class User implements Serializable {

public String userName1;

public String userName2;

public String userName3;

public String userName4;

public String userName5;

public String userName6;

public String userName7;

public String userName8;

public String userName9;

public String userName10;

public String userName11;

public String userName12;

public String userName13;

public String userName14;

public String userName15;

public String userName16;

}

}

2.top命令查看cpu占用率top - 09:56:17 up 1 day, 9:53, 7 users, load average: 1.34, 0.95, 0.77

Tasks: 139 total, 2 running, 137 sleeping, 0 stopped, 0 zombie

%Cpu(s): 51.9 us, 3.8 sy, 0.0 ni, 43.6 id, 0.0 wa, 0.0 hi, 0.7 si, 0.0 st

KiB Mem : 3880320 total, 137000 free, 3496672 used, 246648 buff/cache

KiB Swap: 2097148 total, 2076660 free, 20488 used. 159388 avail Mem

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

17679 root 20 0 3665040 32140 15900 S 91.0 0.8 0:18.84 java

15862 root 20 0 155032 5624 3936 S 0.7 0.1 0:30.12 sshd

24986 root 20 0 4607680 998.2m 12640 S 0.7 26.3 18:24.92 java

23783 root 20 0 151708 6408 1112 S 0.3 0.2 6:36.31 redis-sentinel

23790 root 20 0 149448 4840 1108 R 0.3 0.1 6:39.38 redis-sentinel

25350 root 20 0 4567896 973220 11788 S 0.3 25.1 12:45.53 java

25716 root 20 0 4574928 994456 11788 S 0.3 25.6 12:47.27 java

28449 root 20 0 155160 5644 3936 S 0.3 0.1 0:22.72 sshd

28610 root 20 0 162832 3032 1572 S 0.3 0.1 0:11.98 top

30011 root 20 0 155148 5628 3936 S 0.3 0.1 0:13.78 sshd

30158 root 20 0 162832 3024 1556 S 0.3 0.1 0:06.20 top

1 root 20 0 128104 4568 2736 S 0.0 0.1 0:04.42 systemd

2 root 20 0 0 0 0 S 0.0 0.0 0:00.04 kthreadd

4 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/0:0H

6 root 20 0 0 0 0 S 0.0 0.0 0:09.35 ksoftirqd/0

3.查看进程对应的线程占用cpu

top -p 23191 -HPID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND

23192 root 20 0 3665040 30560 15772 R 91.3 0.8 2:06.06 java

23191 root 20 0 3665040 30560 15772 S 0.0 0.8 0:00.00 java

23193 root 20 0 3665040 30560 15772 S 0.0 0.8 0:00.01 GC Thread#0

23194 root 20 0 3665040 30560 15772 S 0.0 0.8 0:00.00 G1 Main Marker

23195 root 20 0 3665040 30560 15772 S 0.0 0.8 0:00.00 G1 Conc#0

23196 root 20 0 3665040 30560 15772 S 0.0 0.8 0:00.00 G1 Refine#0

23197 root 20 0 3665040 30560 15772 S 0.0 0.8 0:00.01 G1 Young RemSet

4.获取23191线程堆栈信息

jstack 23191 > 23191.log,找到对应的高cpu占用线程23192(0x5d54)线程的状态。可以通过堆栈信息看到是Test.java中的问题"main" #1 prio=5 os_prio=0 cpu=265491.21ms elapsed=290.57s tid=0x00007f5830014800 nid=0x5d54 runnable [0x00007f58384a3000]

java.lang.Thread.State: RUNNABLE

at Test.main(Test.java:15)

5.上述可以通过top + jstack进行查找高cpu线程和其堆栈信息

也可以通过脚本来实现查询高cpu占用线程wget --no-check-certificate https://github.com/oldratlee/useful-scripts/archive/release-2.x.zip

unzip release-2.x.zip

github上的开源脚本

直接执行

/data/java/useful-scripts-release-2.x/bin中的

show-busy-java-threads脚本即可查看，默认显示前5名线程

结果[1] Busy(90.4%) thread(14366/0x381e) stack of java process(14365) under user(root):

"main" #1 prio=5 os_prio=0 cpu=16787.88ms elapsed=18.53s tid=0x00007f4964014800 nid=0x381e runnable [0x00007f496dc9f000]

java.lang.Thread.State: RUNNABLE

at Test.main(Test.java:15)

[2] Busy(0.0%) thread(14365/0x381d) stack of java process(14365) under user(root):

[3] Busy(0.0%) thread(24040/0x5de8) stack of java process(24040) under user(root):

[4] Busy(0.0%) thread(24043/0x5deb) stack of java process(24040) under user(root):

"main" #1 prio=5 os_prio=0 cpu=787.79ms elapsed=121813.53s tid=0x00007f9e9c015000 nid=0x5deb in Object.wait() [0x00007f9ea6296000]

java.lang.Thread.State: WAITING (on object monitor)

at java.lang.Object.wait(java.base@11.0.7/Native Method)

- waiting on <0x00000000c631f8a0> (a org.apache.zookeeper.server.quorum.QuorumPeer)

at java.lang.Thread.join(java.base@11.0.7/Thread.java:1305)

- waiting to re-lock in wait() <0x00000000c631f8a0> (a org.apache.zookeeper.server.quorum.QuorumPeer)

at java.lang.Thread.join(java.base@11.0.7/Thread.java:1379)

at org.apache.zookeeper.server.quorum.QuorumPeerMain.runFromConfig(QuorumPeerMain.java:171)

at org.apache.zookeeper.server.quorum.QuorumPeerMain.initializeAndRun(QuorumPeerMain.java:114)

at org.apache.zookeeper.server.quorum.QuorumPeerMain.main(QuorumPeerMain.java:81)

[5] Busy(0.0%) thread(24098/0x5e22) stack of java process(24098) under user(root):