模仿问题代码

结构一个死循环,造成CPU使用率100%。
> vim InfiniteLoop.javapublic class InfiniteLoop {    public static void main(String[] args) {        Runnable target;        Thread thread=new Thread(new Runnable() {            @Override            public void run() {                long i=0;                while (true){                    i++;                }            }        });        thread.setName("rumenz");        thread.start();    }}> javac InfiniteLoop.java

运行问题代码

> java InfiniteLoop

发现零碎CPU 100%

> top6076 root      20   0 7096732  18972  10648 S 100.0  0.1   7:42.51 java InfiniteLoop
失去过程号是6076

依据top命令，发现PID为6076的Java过程占用CPU高达100%，呈现故障。

找出具体的线程号

> top -Hp 60766096 root      20   0 7096732  18972  10648 R 99.7  0.1   9:09.92 java
失去线程号是6096

将线程号转换成16进制

> printf "%x\n" 609617d0

万事具备,开始应用jstack打印堆栈信息

> jstack 6076 | grep 17d0 -A 30"rumenz" #10 prio=5 os_prio=0 tid=0x00007fe0580f9000 nid=0x17d0 runnable [0x00007fe04431d000]   java.lang.Thread.State: RUNNABLE        at InfiniteLoop$1.run(InfiniteLoop.java:11)        at java.lang.Thread.run(Thread.java:748)"Service Thread" #9 daemon prio=9 os_prio=0 tid=0x00007fe0580e5800 nid=0x17ce runnable [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"C1 CompilerThread3" #8 daemon prio=9 os_prio=0 tid=0x00007fe0580c8000 nid=0x17cd waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"C2 CompilerThread2" #7 daemon prio=9 os_prio=0 tid=0x00007fe0580c6000 nid=0x17cc waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"C2 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007fe0580c4000 nid=0x17cb waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007fe0580c1000 nid=0x17ca waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007fe0580bf800 nid=0x17c9 runnable [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007fe05808e800 nid=0x17c8 in Object.wait() [0x00007fe044b25000]   java.lang.Thread.State: WAITING (on object monitor)        at java.lang.Object.wait(Native Method)        - waiting on <0x000000076d408ed8> (a java.lang.ref.ReferenceQueue$Lock)        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144)        - locked <0x000000076d408ed8> (a java.lang.ref.ReferenceQueue$Lock)        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165)        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216)
at InfiniteLoop$1.run(InfiniteLoop.java:11),提醒出代码11行, 查看源码发现有一个死循环。

总结解决JAVA,CPU 100%的问题

  • top 查找CPU 100%的过程号pid
  • top -Hp pid找出过程pid下最占CPU的线程号tid
  • printf "%x\n" tid 将tid转换成十六进制 16tid
  • jstack pid | grep 16tid -A 30打印堆栈信息
  • 解决问题代码

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