Java程序CPU占用过高(100%)解决思路和解决方案_java进程cpu占用过高怎么办

1. 线上诊断工具Arthas

详情见之前的BLGO: Web应用线上诊断工具-Arthas

2. 采用JDK自带的jstack进行排查

2.1 使用top查看进程内存占用情况

[root@honor ~]# top
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2.2 使用PS来分析进程和线程的占用情况

• 通过这种方式来找到线程占用高的线程id

[root@honor ~]# ps H -eo pid,tid,%cpu
#grep 后面进行进程id
[root@honor ~]#  ps H -eo pid,tid,%cpu|grep 14937
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• 我们可以看到进程为20059的线程CPU占用偏高

2.3 采用jstack 来进行虚拟机栈的区分

• 使用jstack来查看 jstack PID

[root@honor ~]# jstack 20058
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• 执行过后我们会得到一下内容

2022-04-20 19:42:27
Full thread dump OpenJDK 64-Bit Server VM (25.242-b08 mixed mode):

"Attach Listener" #9 daemon prio=9 os_prio=0 tid=0x00007f9c64001000 nid=0x6c49 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Service Thread" #8 daemon prio=9 os_prio=0 tid=0x00007f9cac12c000 nid=0x4e67 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C1 CompilerThread2" #7 daemon prio=9 os_prio=0 tid=0x00007f9cac121000 nid=0x4e66 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007f9cac11f000 nid=0x4e65 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007f9cac110000 nid=0x4e64 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007f9cac10d800 nid=0x4e63 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007f9cac0e3800 nid=0x4e62 in Object.wait() [0x00007f9c982c5000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x0000000721588668> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144)
        - locked <0x0000000721588668> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165)
        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216)

"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f9cac0df000 nid=0x4e61 in Object.wait() [0x00007f9c983c6000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x0000000721590188> (a java.lang.ref.Reference$Lock)
        at java.lang.Object.wait(Object.java:502)
        at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
        - locked <0x0000000721590188> (a java.lang.ref.Reference$Lock)
        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)

"main" #1 prio=5 os_prio=0 tid=0x00007f9cac04b800 nid=0x4e5b runnable [0x00007f9cb319d000]
   java.lang.Thread.State: RUNNABLE
        at java.io.FileOutputStream.writeBytes(Native Method)
        at java.io.FileOutputStream.write(FileOutputStream.java:326)
        at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
        at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140)
        - locked <0x000000072158dd90> (a java.io.BufferedOutputStream)
        at java.io.PrintStream.write(PrintStream.java:482)
        - locked <0x0000000721584c20> (a java.io.PrintStream)
        at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)
        at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:291)
        at sun.nio.cs.StreamEncoder.flushBuffer(StreamEncoder.java:104)
        - locked <0x0000000721584bd8> (a java.io.OutputStreamWriter)
        at java.io.OutputStreamWriter.flushBuffer(OutputStreamWriter.java:185)
        at java.io.PrintStream.newLine(PrintStream.java:546)
        - eliminated <0x0000000721584c20> (a java.io.PrintStream)
        at java.io.PrintStream.println(PrintStream.java:807)
        - locked <0x0000000721584c20> (a java.io.PrintStream)
        at Hello.main(Hello.java:6)

"VM Thread" os_prio=0 tid=0x00007f9cac0d5000 nid=0x4e60 runnable 

"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007f9cac05e000 nid=0x4e5c runnable 

"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007f9cac05f800 nid=0x4e5d runnable 

"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00007f9cac061800 nid=0x4e5e runnable 

"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00007f9cac063800 nid=0x4e5f runnable 

"VM Periodic Task Thread" os_prio=0 tid=0x00007f9cac12e800 nid=0x4e68 waiting on condition 

JNI global references: 5

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• 注意找关键点 nid(nid 为16进制 线程为10进制)

• 16进制在线转换

• 得到 4e5b 然后去查找该tid 可以得到是哪个占用过高 atHello.main(Hello.java:6)

  

2.4 总结

根据jstack分析得知 当前线程占用过高是因为死循环产生的

3. 分析dump或hprof文件

3.1 生成dump或hprof文件

## 20058为PID
[root@honor ~]#  jmap -dump:file=javaDump.hprof,format=b 20058  
[root@honor ~]# jmap -dump:file=javaDump.dump,format=b 20058
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3.2 使用JDK自带的jvisualvm来分析dump文件

• 目录：C:\Program Files\Java\jdk1.8.0_66\bin
• 此处dump和hprof文件操作步骤相同不一一描述。

3.2.1 导入dump文件

3.2.2 查看hprof文件

• 概要：主要显示基本信息，环境，系统属性及可选择的占用最大的对象
• 类：可分析使用最多的类及其详细信息
• 监视：CPU、内存、类、线程的实时情况
• 线程：可查看线程的使用情况

3.2.2 使用远程来查看