一. 追查cpu占用较高的进程(线程)
1 . 如何查找出当前系统中占用cpu或者内存最高的进程?
ps aux |sort -rn -k 3 |head -n3 查找出当前系统中cpu资源占用前三名的进程, -k 3 表示用ps结果中的第三列排序,ps aux输出结果列顺序为:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND,因此要是按照mem排序使用 k 4
[root@b28-1330 ~]# ps aux |sort -rn -k 3 |head -n3 root 7855 21.1 8.1 8618980 2696340 ? Sl xxxx root 8268 20.9 8.5 8613152 2801708 ? Sl xxxx USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
2. 通过第一步我们确定了占用cpu最高的进程的pid是7855,那么如何确定该进程的线程cpu占用情况呢?
top -Hp 7855 -H 显示线程 -p 指定pid 如果执行上述命令之后,发现还有一个进程,那么按下 shift+H, 即可显示threads
root@b28-1330 ~]# top -Hp 7855 top - 14:09:41 up 330 days, 22:33, 4 users, load average: 0.73, 0.81, 0.71 Tasks: 5416 total, 0 running, 5416 sleeping, 0 stopped, 0 zombie Cpu(s): 2.9%us, 0.6%sy, 0.0%ni, 96.4%id, 0.0%wa, 0.0%hi, 0.2%si, 0.0%st Mem: 32933092k total, 30577956k used, 2355136k free, 438232k buffers Swap: 16779884k total, 0k used, 16779884k free, 22525628k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 7906 root 15 0 8416m 2.6g 11m S 3.9 8.2 16:58.92 java 21006 root 15 0 8416m 2.6g 11m S 3.2 8.2 9:59.56 java 21019 root 15 0 8416m 2.6g 11m S 2.9 8.2 9:55.70 java
经过排查,我们发现 tid(Thread Id)为7906线程占用cpu最高
3. 上一步我们已经找到了占用cpu最高的线程,那么我们下面要确定一下这个线程的详细信息
我们使用 jstack来进行深度追踪:
将tid 7906转换为十六进制: printf "%x " --> 1ee2
使用命令 jstack 7855 |grep -i 1ee2 -A 20 来查询进程详细信息:
[root@b28-1330 ~]# jstack 7855 |grep -i 1ee2 -A 20 "New I/O client worker #1-1" daemon prio=10 tid=0x000000005ad02000 nid=0x1ee2 runnable [0x0000000043972000] java.lang.Thread.State: RUNNABLE at sun.nio.ch.EPollArrayWrapper.epollWait(Native Method) at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:210) at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:65) at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:69) - locked <0x00000007801074a0> (a sun.nio.ch.Util$2) - locked <0x0000000780107490> (a java.util.Collections$UnmodifiableSet) - locked <0x00000007800fbcc0> (a sun.nio.ch.EPollSelectorImpl) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:80) at org.jboss.netty.channel.socket.nio.SelectorUtil.select(SelectorUtil.java:38) at org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:163) at org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108) at org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:44) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662)
ok这个线程的堆栈信息就出来了...
二. 如何查看占用JVM内存最大的前20个class实例对象
主要用到jmap 和sort命令
[root@b28-1330 ~]# jmap -histo 7855 |sort -rn -k3|head -n11 Total 6221631 455243264 1: 111761 95387048 [B 2: 884396 63940104 [C 3: 52573 52139904 [I 4: 680476 21775232 java.lang.String 5: 120038 17978192 <constMethodKlass> 6: 120038 16335920 <methodKlass> 7: 11558 12871496 <constantPoolKlass> 8: 103599 12431880 java.net.SocksSocketImpl 9: 350199 11206368 java.util.HashMap$Entry 10: 167532 9294056 <symbolKlass>