cpu打到100的分析 | 字数总计: 2.5k | 阅读时长: 12分钟 | 阅读量:
CPU 飙升是一个常见的问题。
CPU100%定位的两大神器
想要定位到具体是哪一行的代码导致， 一般都会使用下面的两大神器
通常使用的jvm自带的工具jstack，
还有一种就是开源神器arthas，
一般而言，arthas还有其它的功能，所以选择它多一点.
CPU 飙升100%的解决思路****与方法论
使用jstack 解决CPU 100%问题实操 使用jstack 解决CPU 100%问题，在方法论上要用到两个命令，
top 命令查看TOP N线程，
jstack命令查看堆栈信息
1.jstack命令讲解 命令jstack是java堆栈的跟踪工具，可以打印出程序中所有线程的堆栈信息，包括线程状态，调用栈信息，锁信息等。
jstack可以诊断线程死锁、内存泄漏等问题
命令格式: jstack [options] pid
常用例子: jstack -l pid，查看线程的堆栈信息
堆栈信息解读:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 [root@192-168-65-185 ~]# jstack -l 294402024-12-17 13:48:51Full thread dump OpenJDK 64-Bit Server VM (25.412-b08 mixed mode): "Attach Listener" #12 daemon prio=9 os_prio=0 tid=0x00007f097c001000 nid=0x763a runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "DestroyJavaVM" #11 prio=5 os_prio=0 tid=0x00007f09e004b800 nid=0x7301 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "pool-1-thread-1" #10 prio=5 os_prio=0 tid=0x00007f09e0166000 nid=0x7316 runnable [0x00007f09cc9cb000] java.lang.Thread.State: RUNNABLE at com.tuling.learnjuc.demo.JVMCPU$CPUTask.run(JVMCPU.java:16) - locked <0x0000000757d645b8> (a java.lang.Object) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:750) Locked ownable synchronizers: - <0x0000000757d65d00> (a java.util.concurrent.ThreadPoolExecutor$Worker) "Service Thread" #9 daemon prio=9 os_prio=0 tid=0x00007f09e0140000 nid=0x7314 runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "C1 CompilerThread3" #8 daemon prio=9 os_prio=0 tid=0x00007f09e0133000 nid=0x7313 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "C2 CompilerThread2" #7 daemon prio=9 os_prio=0 tid=0x00007f09e0131000 nid=0x7312 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "C2 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007f09e012f000 nid=0x7311 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007f09e012c800 nid=0x7310 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007f09e011e000 nid=0x730f runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007f09e00f2000 nid=0x730e in Object.wait() [0x00007f09cd1d3000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x0000000757d08f00> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144) - locked <0x0000000757d08f00> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:188) Locked ownable synchronizers: - None "Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f09e00ed000 nid=0x730d in Object.wait() [0x00007f09cd2d4000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x0000000757d06b98> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:502) at java.lang.ref.Reference.tryHandlePending(Reference.java:191) - locked <0x0000000757d06b98> (a java.lang.ref.Reference$Lock) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153) Locked ownable synchronizers: - None "VM Thread" os_prio=0 tid=0x00007f09e00e3800 nid=0x730c runnable "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007f09e005e000 nid=0x7302 runnable "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007f09e0060000 nid=0x7303 runnable "GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00007f09e0062000 nid=0x7304 runnable "GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00007f09e0064000 nid=0x7305 runnable "GC task thread#4 (ParallelGC)" os_prio=0 tid=0x00007f09e0065800 nid=0x7306 runnable "GC task thread#5 (ParallelGC)" os_prio=0 tid=0x00007f09e0067800 nid=0x7307 runnable "GC task thread#6 (ParallelGC)" os_prio=0 tid=0x00007f09e0069800 nid=0x7308 runnable "GC task thread#7 (ParallelGC)" os_prio=0 tid=0x00007f09e006b800 nid=0x7309 runnable "GC task thread#8 (ParallelGC)" os_prio=0 tid=0x00007f09e006d000 nid=0x730a runnable "GC task thread#9 (ParallelGC)" os_prio=0 tid=0x00007f09e006f000 nid=0x730b runnable "VM Periodic Task Thread" os_prio=0 tid=0x00007f09e0142800 nid=0x7315 waiting on condition JNI global references: 5
你会发现上面的信息其实是一段一段的，摘取其中的一段为大家说明:
1 2 "pool-1-thread-1" Locked ownable synchronizers: - <0x0000000757d65d00> (a java.util.concurrent.ThreadPoolExecutor$Worker )
pool-1-thread-1:线程名称
#1:当前线程ID，从main开始，jvm会根据线程创建的顺序为其线程编号
prio:优先级的顺序，一般默认是5
os_prio:线程对应系统的优先级
tid:java内的线程id
nid:操作系统级别的线程id，是一个十六进制
关于线程的信息:
NEW:线程新建，还没开始运行
RUNNABLE:正在java虚拟机中运行的线程
BLOCKED:被阻塞，正在等待监视器锁的线程
WAITING:无限期等待另一个线程执行特定操作的线程
TIMED_WAITING:等待另一个线程执行操作达到指定等待时间的线程
TERMINATED:已经退出的线程
我们这里关注的最多的就是nid
2.使用jstack解决CPU占用很高的问题并定位具体行数 先来看一段代码:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 package com.tuling.learnjuc.demo;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;public class JVMCPU { private static ExecutorService service = Executors.newFixedThreadPool(5 ); private static Object lock = new Object (); public static class CPUTask implements Runnable { @Override public void run () { synchronized (lock){ l ong sum = 0L ; while (true ){ sum +=1 ; } } } } public static void main (String[] args) { CPUTask cpuTask = new CPUTask (); service.execute(cpuTask); } }
将这段代码上传到linux服务器上编译
注意：如果提示javac: 未找到命令… ，执行yum install java-1.8.0-openjdk-devel
使用nohup java com.tuling.learnjuc.demo.JVMCPU &运行
使用top命令可以看到cpu被打满了
知道了进程的PID，如何找到进程下是哪个线程呢?可以使用命令top -Hp 32208，如下所示
如果能获取到线程名，下面这步可以忽略，不需要根据线程id找线程
从上面的图可以看到，cpu占用最多的线程是32230这个线程id，接下来就是使用jstack命令来查看程序的所有堆栈信息，但是，这里需要有一个注意的点，32230这个是一个十进制的，使用jstack看到的nid是十六进制，所以我们需要转换，可以使用printf “%x\n”这个命令
接下来使用jstack -l 32208打印堆栈信息
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 [root@192-168-65-185 ~] "Attach Listener" Locked ownable synchronizers: - None "DestroyJavaVM" Locked ownable synchronizers: - None "pool-1-thread-1" Locked ownable synchronizers: - <0x0000000757d65d00> (a java.util.concurrent.ThreadPoolExecutor$Worker ) "Service Thread" Locked ownable synchronizers: - None "C1 CompilerThread3" Locked ownable synchronizers: - None "C2 CompilerThread2" Locked ownable synchronizers: - None "C2 CompilerThread1" Locked ownable synchronizers: - None "C2 CompilerThread0" Locked ownable synchronizers: - None "Signal Dispatcher" Locked ownable synchronizers: - None "Finalizer" Locked ownable synchronizers: - None "Reference Handler" Locked ownable synchronizers: - None "VM Thread" os_prio=0 tid=0x00007fb4fc0e3800 nid=0x7ddc runnable "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007fb4fc05e000 nid=0x7dd2 runnable "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007fb4fc060000 nid=0x7dd3 runnable "GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00007fb4fc062000 nid=0x7dd4 runnable "GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00007fb4fc064000 nid=0x7dd5 runnable "GC task thread#4 (ParallelGC)" os_prio=0 tid=0x00007fb4fc065800 nid=0x7dd6 runnable "GC task thread#5 (ParallelGC)" os_prio=0 tid=0x00007fb4fc067800 nid=0x7dd7 runnable "GC task thread#6 (ParallelGC)" os_prio=0 tid=0x00007fb4fc069800 nid=0x7dd8 runnable "GC task thread#7 (ParallelGC)" os_prio=0 tid=0x00007fb4fc06b800 nid=0x7dd9 runnable "GC task thread#8 (ParallelGC)" os_prio=0 tid=0x00007fb4fc06d000 nid=0x7dda runnable "GC task thread#9 (ParallelGC)" os_prio=0 tid=0x00007fb4fc06f000 nid=0x7ddb runnable "VM Periodic Task Thread" os_prio=0 tid=0x00007fb4fc142800 nid=0x7de5 waiting on condition JNI global references: 5
从上面的信息中，可以看到转换的结果和nid是一致的，
从下面的信息中就可以看到问题其实是出现在JVMCPU.java的16行左右，这里给出的是16行，但是实际情况是16行的附近
1 2 "pool-1-thread-1" Locked ownable synchronizers: - <0x0000000757d65d00> (a java.util.concurrent.ThreadPoolExecutor$Worker )
结合代码来看一下就很容易问题
使用arthas解决CPU占用很高的问题，定位具体代码行
官方文档：https://arthas.aliyun.com/
使用arthas解决CPU 100%问题，在方法论上要用到两个命令，
dashboard 命令查看TOP N线程，
thread 命令查看堆栈信息
先来运行arthas
1 curl -O https://arthas.aliyun.com/arthas-boot.jarjava -jar arthas-boot.jar
输入1显示如下
输入dashboard命令可以看到是哪个线程占用cpu最高
接下来输入thread -n 1，表示最忙的线程并打印信息
从上面的图中可以看到arthas和jstack展示的信息差不多，都定位到了JVMCPU.java的16行程序
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