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上篇在查看多线程死锁问题的时候，我们用到了jstack命令。Linux有一些相关的命令可以查看进程情况，本文做一下稍微的记录。
简单写段代码造成CPU满，和前文中的筷子类联动下（不用白不用）
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public class App {
public static void main(String[] args) {
while(true) {
Chopsticks cs1 = new Chopsticks(1);
}
}
}
- top 命令 - 直接一个top命令，看到 PID为4832的这个进程把CPU跑满了
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top - 09:16:54 up 22 min, 2 users, load average: 1.05, 1.15, 0.86
Tasks: 193 total, 2 running, 191 sleeping, 0 stopped, 0 zombie
%Cpu(s): 39.8 us, 0.8 sy, 0.0 ni, 59.4 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem: 8175896 total, 2947052 used, 5228844 free, 90280 buffers
KiB Swap: 4191228 total, 0 used, 4191228 free. 1069516 cached Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4832 wildmeo+ 20 0 4296188 31944 16424 S 100.2 0.4 1:46.70 java
2132 wildmeo+ 20 0 1450044 218880 66640 S 15.1 2.7 6:42.40 compiz
1077 root 20 0 457804 139540 38524 S 5.2 1.7 1:34.39 Xorg
4807 wildmeo+ 20 0 587904 30652 23516 S 2.6 0.4 0:00.83 gnome-terminal
1840 wildmeo+ 20 0 123408 3188 2800 S 0.4 0.0 0:02.20 VBoxClient
4575 wildmeo+ 20 0 5799608 675708 70524 S 0.4 8.3 2:02.68 java
4851 wildmeo+ 20 0 29152 3384 2864 R 0.4 0.0 0:00.18 top
后边进程省略
- ps 命令 - 跑一把ps命令可以看到其具体出问题的线程
命令ps -mp 4832 -o THREAD,tid,time ， 查询得到线程TID 4834
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wildmeowth@wildmeowth-VirtualBox:~$ ps -mp 4832 -o THREAD,tid,time
USER %CPU PRI SCNT WCHAN USER SYSTEM TID TIME
wildmeo+ 99.3 - - - - - - 00:02:46
wildmeo+ 0.0 19 - futex_ - - 4832 00:00:00
wildmeo+ 99.2 19 - - - - 4834 00:02:46
wildmeo+ 0.0 19 - futex_ - - 4835 00:00:00
wildmeo+ 0.0 19 - futex_ - - 4840 00:00:00
wildmeo+ 0.0 19 - futex_ - - 4841 00:00:00
wildmeo+ 0.0 19 - futex_ - - 4842 00:00:00
wildmeo+ 0.0 19 - futex_ - - 4843 00:00:00
wildmeo+ 0.0 19 - futex_ - - 4844 00:00:00
wildmeo+ 0.0 19 - futex_ - - 4845 00:00:00
wildmeo+ 0.0 19 - futex_ - - 4846 00:00:00
wildmeo+ 0.0 19 - futex_ - - 4847 00:00:00
wildmeo+ 0.0 19 - futex_ - - 4848 00:00:00
wildmeo+ 0.0 19 - futex_ - - 4849 00:00:00
顺便转下16进制方便查询
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wildmeowth@wildmeowth-VirtualBox:~$ printf "%x\n" 4834
12e2
- jstack 命令 - jdk 自带jstack 查看Java进程和线程的具体信息
jstack 4832 | grep -25 12e2
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wildmeowth@wildmeowth-VirtualBox:~$ jstack 4832 | grep -25 12e2
2022-03-24 09:23:28
"Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007f9c4c082000 nid=0x12ec in Object.wait() [0x00007f9c339f8000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000000d6608ee0> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
- locked <0x00000000d6608ee0> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)
"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f9c4c07d800 nid=0x12eb in Object.wait() [0x00007f9c33af9000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000000d6606b50> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:502)
at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
- locked <0x00000000d6606b50> (a java.lang.ref.Reference$Lock)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
"main" #1 prio=5 os_prio=0 tid=0x00007f9c4c00a000 nid=0x12e2 runnable [0x00007f9c542c8000]
java.lang.Thread.State: RUNNABLE
at com.wildemeowth.thread.App.main(App.java:23)
"VM Thread" os_prio=0 tid=0x00007f9c4c076000 nid=0x12ea runnable
JNI global references: 11
- jps 命令 - 我们也可以用Java 自带的jps 稍加观察
可以简单看出是 App类进程搞的坏事
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wildmeowth@wildmeowth-VirtualBox:~$ jps
4832 App
4859 Jps
最后顺便 kill 4832 把它杀了