JVM基础篇-线程运行诊断
CPU占用过多定位
- 用top定位哪个进程对cpu的占用过高
- ps H -eo pid,tid,%cpu | grep 进程id （用ps命令进一步定位是哪个线程引起的cpu占用过高）
- jstack 进程id 可以根据线程id 找到有问题的线程，进一步定位到问题代码的源码行号
程序运行很长时间没有结果
- 使用
jps查找java进程id - 使用jstack 进程id查看异常信息
示例
package com.vmware.stack;class A {}class B {}public class Demo4 {static A a = new A();static B b = new B();public static void main(String[] args) throws InterruptedException {new Thread(() -> {synchronized (a) {try {Thread.sleep(2000);} catch (InterruptedException e) {e.printStackTrace();}synchronized (b) {System.out.println("获取了a和b");}}}).start();Thread.sleep(1000);new Thread(() -> {synchronized (b) {synchronized (a) {System.out.println("获得了a和b");}}}).start();}
}
jstack info
Found one Java-level deadlock:
=============================
"Thread-0":waiting to lock monitor 0x00007f90a8000ff0 (object 0x000000071a9cb480, a com.vmware.stack.B),which is held by "Thread-1""Thread-1":waiting to lock monitor 0x00007f909c000ff0 (object 0x000000071a9ca6a0, a com.vmware.stack.A),which is held by "Thread-0"Java stack information for the threads listed above:
===================================================
"Thread-0":at com.vmware.stack.Demo4.lambda$main$0(Demo4.java:24)- waiting to lock <0x000000071a9cb480> (a com.vmware.stack.B)- locked <0x000000071a9ca6a0> (a com.vmware.stack.A)at com.vmware.stack.Demo4$$Lambda$14/0x0000000800c01618.run(Unknown Source)at java.lang.Thread.run(java.base@17.0.6/Thread.java:833)
"Thread-1":at com.vmware.stack.Demo4.lambda$main$1(Demo4.java:32)- waiting to lock <0x000000071a9ca6a0> (a com.vmware.stack.A)- locked <0x000000071a9cb480> (a com.vmware.stack.B)at com.vmware.stack.Demo4$$Lambda$17/0x0000000800c01838.run(Unknown Source)at java.lang.Thread.run(java.base@17.0.6/Thread.java:833)Found 1 deadlock.
)
