linux cpu过高原因及代码定位

1. top命令查看CPU和内存占用率

top回车，然后按1

发现进程PID 35163 CPU和内存占用率都很高

top - 06:13:47 up  5:31,  1 user,  load average: 2.11, 2.07, 2.06
Tasks: 189 total,   1 running, 188 sleeping,   0 stopped,   0 zombie
Cpu0  : 22.3%us,  0.7%sy,  0.0%ni, 76.4%id,  0.3%wa,  0.3%hi,  0.0%si,  0.0%st
Cpu1  :100.0%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu2  :  8.0%us,  0.3%sy,  0.0%ni, 91.7%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu3  : 70.4%us,  1.7%sy,  0.0%ni, 25.6%id,  2.3%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   1012292k total,   943076k used,    69216k free,     9372k buffers
Swap:  1675260k total,   375204k used,  1300056k free,    34024k cached

PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
35163 user111   20   0 3823m 360m 6828 S 199.5 36.5 147:41.46 java

另外，top下，按H可以在进程PID和线程TID之间切换

2. 查看PID对应的进程

[user111@kms210 lms]$ ps -ef|grep 35163
user111  35163     1 99 04:59 pts/0    02:28:06 /usr/local/jdk1.8.0_60/bin/java -Djava.util.logging.config.file=/usr/local/lms/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.awt.headless=true -Djava.endorsed.dirs=/usr/local/lms/endorsed -classpath /usr/local/lms/bin/bootstrap.jar:/usr/local/lms/bin/tomcat-juli.jar -Dcatalina.base=/usr/local/lms -Dcatalina.home=/usr/local/lms -Djava.io.tmpdir=/usr/local/lms/temp org.apache.catalina.startup.Bootstrap start
user111  44605 23049  0 06:14 pts/0    00:00:00 grep 35163

3. 查看线程35163中占用CPU高的进程

[user111@kms210 lms]$ ps -mp 35163 -o THREAD,tid,time
USER     %CPU PRI SCNT WCHAN  USER SYSTEM   TID     TIME
user111   199   -    - -         -      -     - 02:32:04
user111   0.0  19    - futex_    -      - 35163 00:00:00
user111   0.0  19    - poll_s    -      - 35164 00:00:01
user111   0.0  19    - futex_    -      - 35165 00:00:01
user111   0.0  19    - futex_    -      - 35166 00:00:00
user111   0.0  19    - futex_    -      - 35167 00:00:00
user111   0.0  19    - futex_    -      - 35168 00:00:00
user111   0.3  19    - futex_    -      - 35169 00:00:16
user111   0.3  19    - futex_    -      - 35170 00:00:16
user111   0.1  19    - futex_    -      - 35171 00:00:05
user111   0.0  19    - futex_    -      - 35172 00:00:00
user111   0.0  19    - futex_    -      - 35173 00:00:01
user111   0.0  19    - futex_    -      - 35174 00:00:00
user111   0.0  19    - futex_    -      - 35178 00:00:00
user111   0.0  19    - ep_pol    -      - 35181 00:00:00
user111   0.0  19    - ep_pol    -      - 35182 00:00:00
user111   0.0  19    - ep_pol    -      - 35183 00:00:00
user111  99.6  19    - -         -      - 35204 01:15:33
user111   0.0  19    - futex_    -      - 35222 00:00:00
user111  99.6  19    - -         -      - 35226 01:15:27
user111   0.0  19    - futex_    -      - 35230 00:00:00

线程TID转16进制

[user111@kms210 lms]$ printf "%x\n" 35204
8984

4.查看线程栈信息

[user111@kms210 lms]$ jstack 35163 | grep 8984 -A 30
"Thread-6" #18 daemon prio=5 os_prio=0 tid=0x00007fb0d8fd1800 nid=0x8984 runnable [0x00007fb11cc8e000]
java.lang.Thread.State: RUNNABLE
at com.qsd.sssm.thread.LmsThread.run(LmsThread.java:68)

"NioBlockingSelector.BlockPoller-3" #15 daemon prio=5 os_prio=0 tid=0x00007fb130531800 nid=0x896f runnable [0x00007fb11dfb2000]
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:79)
at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
- locked <0x00000000f62278e8> (a sun.nio.ch.Util$2)
- locked <0x00000000f62278f8> (a java.util.Collections$UnmodifiableSet)
- locked <0x00000000f62278a0> (a sun.nio.ch.EPollSelectorImpl)
at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
at org.apache.tomcat.util.net.NioBlockingSelector$BlockPoller.run(NioBlockingSelector.java:342)

"NioBlockingSelector.BlockPoller-2" #14 daemon prio=5 os_prio=0 tid=0x00007fb130517000 nid=0x896e runnable [0x00007fb11e0b3000]
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:79)
at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
- locked <0x00000000f6227b20> (a sun.nio.ch.Util$2)
- locked <0x00000000f6227b30> (a java.util.Collections$UnmodifiableSet)
- locked <0x00000000f6227ad8> (a sun.nio.ch.EPollSelectorImpl)
at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
at org.apache.tomcat.util.net.NioBlockingSelector$BlockPoller.run(NioBlockingSelector.java:342)

"NioBlockingSelector.BlockPoller-1" #13 daemon prio=5 os_prio=0 tid=0x00007fb130474800 nid=0x896d runnable [0x00007fb11e3cd000]
java.lang.Thread.State: RUNNABLE
at sun.nio.ch.EPollArrayWrapper.epollWait(Native Method)
[user111@kms210 lms]$

找到出现问题的代码，并分析具体函数中是否有可能出现死循环的代码段。

通常问题出现在while， for之类的循环代码片段。

5. 查看文件LmsThread.java:68行

Debug一下，发现死循环

while (true) {

if(CMD. remoteIp .equals("")) {// 第58行，if成立，死循环

continue;

}

6. 另外，只替换.war文件可能存在的问题

修改只替换.war文件，可能会发现线程占用率还是很高，线程栈信息仍然显示以前的行号的话，可以试试完整的删除项目文件夹，重新部署整个项目

参考地址：http://blog.csdn.net/chenhaotong/article/details/51991786