如何定位消耗CPU最多的线程

xiaoxiao2026-04-25 7

之前有朋友反馈说发的内容希望有个梯度，逐步加深，前面发了几篇关于jvm源码分析的文章，可能我觉得我已经把内容写得浅显易懂了，但是对于某些没怎么接触的同学来说还是比较难理解，这个我以后慢慢改进吧，今天发篇轻松点的文章，可能大家在工作过程中也会可能碰到类似的问题，或许有经验的同学看到这个题目就知道我要说什么了，也有自己的定位方法。

话不多说了，先来看代码吧

public class Test{ public static void main(String args[]){ for(int i=0;i<10;i++){ new Thread(){ public void run(){ try{ Thread.sleep(100000); }catch(Exception e){} } }.start(); } Thread t=new Thread(){ public void run(){ int i=0; while(true){ i=(i++)/100; } } }; t.setName("Busiest Thread"); t.start(); } }

这个例子里新创建了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，可以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？

首先我们可以通过top -Hp <pid>来看这个进程里所有线程的cpu消耗情况，得到类似下面的数据

$ 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

拿到这个结果之后，我们可以看到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

接着我们可以通过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) ...

上面的线程栈我们注意到nid的值其实就是线程ID，它是十六进制的，我们将消耗cpu最高的线程18250，转成十六进制0X47A，然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

最新回复(0)