Linux find which Java thread consuming cpu 2017-12-18 08:17

Sometimes Java process used 100% or 200% CPU. It depends on the core number of your CPU. If your CPU has 8 cores that means the highest usage of a process is 800%. When Java process consuming most CPU you can use the following steps to find which Java threads is consuming the most CPU.

1. Use top command to find which Java process use most CPU and get the process id(PID).

top - 20:57:30 up 419 days,  8:31,  3 users,  load average: 0.13, 0.21, 0.18
Tasks: 517 total,   2 running, 515 sleeping,   0 stopped,   0 zombie
Cpu(s):  6.5%us,  4.7%sy,  0.0%ni, 88.5%id,  0.0%wa,  0.0%hi,  0.3%si,  0.0%st
Mem:  132043276k total, 129229128k used,  2814148k free,   525172k buffers
Swap: 12582904k total,        0k used, 12582904k free, 74824960k cached

   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                              
 31139 work      20   0 31.7g 3.7g  29m S 81.5  2.9 175:29.48 java                                                  
154940 work      20   0 22.2g 5.1g  20m S 47.5  4.0   2093:09 java                                                  
196098 work      20   0 24.5g 5.4g  26m S 20.8  4.3   2691:57 java                                                  
153662 root      20   0  160m 6672 2944 R 18.1  0.0   0:00.55 python                                                
119580 work      20   0 31.7g 3.6g  20m S  8.2  2.9 593:02.50 java                                                  
 12933 work      20   0 29.4g 3.0g  28m S  7.9  2.4  26:16.11 java                                                  
 90888 work      20   0 21.6g 2.8g  24m S  4.6  2.2 348:13.82 java                                                  
102742 work      20   0 30.4g 6.7g  28m S  3.3  5.3 211:09.18 java  

2. Save the result of jstack.

jstack 31139 > /tmp/jstack31139

3. Use top -H -p 31139 to show which Java thread consuming most CPU and get the PID.

top - 20:55:13 up 419 days,  8:29,  3 users,  load average: 0.31, 0.27, 0.20
Tasks: 4861 total,   0 running, 4861 sleeping,   0 stopped,   0 zombie
Cpu(s):  2.5%us,  1.0%sy,  0.0%ni, 96.3%id,  0.0%wa,  0.0%hi,  0.1%si,  0.0%st
Mem:  132043276k total, 129113652k used,  2929624k free,   525156k buffers
Swap: 12582904k total,        0k used, 12582904k free, 74714344k cached

   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                              
 31159 work      20   0 31.7g 3.7g  29m S  5.1  2.9   0:23.24 java                                                  
 31163 work      20   0 31.7g 3.7g  29m S  5.1  2.9   0:22.99 java                                                  
 31151 work      20   0 31.7g 3.7g  29m S  3.4  2.9   0:23.19 java                                                  
 31155 work      20   0 31.7g 3.7g  29m S  3.4  2.9   0:23.43 java                                                  
 31156 work      20   0 31.7g 3.7g  29m S  3.4  2.9   0:23.25 java                                                  
 31157 work      20   0 31.7g 3.7g  29m S  3.4  2.9   0:23.44 java                                                  
 31158 work      20   0 31.7g 3.7g  29m S  3.4  2.9   0:23.16 java                                                  
 31166 work      20   0 31.7g 3.7g  29m S  3.4  2.9   0:23.19 java                                                  
 31169 work      20   0 31.7g 3.7g  29m S  3.4  2.9   0:23.35 java                                                  

4. Get the hexadecimal of thread id in last step.

printf 0x%x 32036 # will get 0x7d24

5. Use vi to find thread id(0x7d24) in jstack file.

"pool-2-thread-1" #274 prio=5 os_prio=0 tid=0x00007f042c128000 nid=0x7d24 waiting on condition [0x00007f02f8fa6000]
   java.lang.Thread.State: WAITING (parking)
    at sun.misc.Unsafe.park(Native Method)
    - parking to wait for  <0x00000004878b1498> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
    at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
    at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1081)
    at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)
    at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

Summary

find high CPU process id -> get jstack output file -> get high thread id -> get hexadecimal nid(thread id) -> find java code in jstack output file

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