java jstack和jmap的基本使用

小咪咪 2022-11-12 08:20 330阅读 0赞

1、jps -lmv 查找要分析的java进程
    
    2、查出最耗CPU线程 top -Hp pid  ( top -Hp 73838)
    126453 root      20   0   16.6g   6.5g      0 S  2.2 20.6   0:19.31 java
    126243 root      20   0   16.6g   6.5g      0 S  1.9 20.6   0:26.59 java
     84628 root      20   0   16.6g   6.5g      0 S  1.6 20.6   0:08.29 java
    118500 root      20   0   16.6g   6.5g      0 S  0.9 20.6   0:32.64 java
    126340 root      20   0   16.6g   6.5g      0 S  0.9 20.6   0:20.54 java
    126536 root      20   0   16.6g   6.5g      0 S  0.9 20.6   0:25.99 java
     84656 root      20   0   16.6g   6.5g      0 S  0.9 20.6   0:07.01 java
     90628 root      20   0   16.6g   6.5g      0 S  0.9 20.6   0:00.80 java
     75241 root      20   0   16.6g   6.5g      0 S  0.6 20.6   4:23.77 java
     75363 root      20   0   16.6g   6.5g      0 S  0.6 20.6  92:06.08 java
      5138 root      20   0   16.6g   6.5g      0 S  0.6 20.6   0:19.65 java
     90617 root      20   0   16.6g   6.5g      0 S  0.6 20.6   0:00.86 java
    3、通过线程ID转换16进制，printf "%x\n" tid
     printf "%x\n" 126453  (1edf5)
    
    4、追踪线程内部，查看load过高原因。通过命令： jstack 73838 > /tmp/tinfo.txt，将线程堆里面的信息全部保存下来
    
    5、通过转换的16进制 就可以去tinfo.txt 里面查找对应的线程
    "https-jsse-nio-8080-exec-1930" #2459769 daemon prio=5 os_prio=0 tid=0x00007fd288bac000 nid=0x1edf5 waiting on condition [0x00007fd0d8994000]
       java.lang.Thread.State: TIMED_WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x00000005d916b4c8> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)
            at java.util.concurrent.LinkedBlockingQueue.poll(LinkedBlockingQueue.java:467)
            at org.apache.tomcat.util.threads.TaskQueue.poll(TaskQueue.java:89)
            at org.apache.tomcat.util.threads.TaskQueue.poll(TaskQueue.java:33)
            at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1073)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
            at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
            at java.lang.Thread.run(Thread.java:748)
    6、jmap 进程id(73838)  得到实例在内存中的使用情况
        jmap -histo:live 73838 > /tmp/jmap.txt
           more /tmp/jmap.txt |grep hanshow| head -n 100   # 查看前100个