java的CPU使用达到100%咋排查
作者：互联网
java的CPU使用达到100%咋排查
面试的时候好像问过两次，没有一次答得比较靠谱，今天就对着网上的博客，自己手动操作一遍，并记录一下。
javaCPU 100%的原因
1： 死循环
2：CPU密集型计算
死循环的java代码
public class TestCPU100 {
static class MyThread extends Thread {
public void run() {
int i = 0;
while (true) {
i++;
}
}
}
public static void main(String args[]) throws InterruptedException {
new MyThread().start();
Thread.sleep(1000*60);
}
}
javac java
[root@localhost home]# javac TestCPU100.java
[root@localhost home]# ll
total 12
-rw-r--r-- 1 root root 494 Feb 27 12:48 TestCPU100.class
-rw-r--r-- 1 root root 380 Feb 27 12:47 TestCPU100.java
-rw-r--r-- 1 root root 345 Feb 27 12:48 TestCPU100$MyThread.class
drwx------. 2 tom tom 62 Apr 11 2018 tom
[root@localhost home]#
[root@localhost home]#
[root@localhost home]#
[root@localhost home]#
[root@localhost home]#
[root@localhost home]#
[root@localhost home]#
[root@localhost home]#
[root@localhost home]# java TestCPU100
top 查进程
可以看到11826 root 20 0 6726996 22968 10272 S 100.3 0.1 0:16.97 java
100%的java进程是pid=11826
[root@localhost ~]# top
top - 12:48:28 up 6 days, 21:16, 8 users, load average: 0.22, 0.06, 0.06
Tasks: 188 total, 1 running, 184 sleeping, 3 stopped, 0 zombie
%Cpu(s): 25.3 us, 0.3 sy, 0.0 ni, 73.8 id, 0.0 wa, 0.0 hi, 0.0 si, 0.6 st
KiB Mem : 16425988 total, 6402548 free, 7889164 used, 2134276 buff/cache
KiB Swap: 6160380 total, 6160380 free, 0 used. 8340448 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
11826 root 20 0 6726996 22968 10272 S 100.3 0.1 0:16.97 java
1763 root 20 0 8038880 1.1g 15328 S 0.7 7.1 43:50.02 java
1901 root 20 0 8038728 987.4m 15272 S 0.7 6.2 43:33.38 java
23650 root 20 0 7855940 1.5g 13732 S 0.7 9.5 33:14.01 java
11929 root 20 0 162016 2296 1536 R 0.3 0.0 0:00.05 top
23482 root 20 0 0 0 0 S 0.3 0.0 0:44.09 kworker/0:2
24375 root 20 0 7961052 1.1g 14040 S 0.3 6.8 7:30.25 java
1 root 20 0 125696 4112 2500 S 0.0 0.0 0:04.83 systemd
................
[root@localhost ~]#
top 查线程
可以看到是11841 root 20 0 6793560 27204 10372 R 99.9 0.2 1:52.16 java 线程11841 的CPU是99%
[root@localhost ~]# top -p 11826 -H
top - 12:50:03 up 6 days, 21:18, 8 users, load average: 0.98, 0.40, 0.18
Threads: 17 total, 1 running, 16 sleeping, 0 stopped, 0 zombie
%Cpu0 : 2.0 us, 2.0 sy, 0.0 ni, 95.9 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
%Cpu1 :100.0 us, 0.0 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
%Cpu2 : 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
%Cpu3 : 2.0 us, 2.0 sy, 0.0 ni, 94.0 id, 0.0 wa, 0.0 hi, 0.0 si, 2.0 st
KiB Mem : 16425988 total, 6396032 free, 7892984 used, 2136972 buff/cache
KiB Swap: 6160380 total, 6160380 free, 0 used. 8336440 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
11841 root 20 0 6793560 27204 10372 R 99.9 0.2 1:52.16 java
11826 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11827 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.05 java
11828 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11829 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11830 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11831 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11832 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11833 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11834 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11835 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11836 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11837 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11838 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11839 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
11840 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.05 java
12182 root 20 0 6793560 27204 10372 S 0.0 0.2 0:00.00 java
线程ID对应的十六进制
[root@localhost ~]# printf "%x\n" 11841
2e41
jstack 查看线程
[root@localhost ~]# jstack 11826
2021-02-27 12:48:59
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.281-b09 mixed mode):
"Attach Listener" #10 daemon prio=9 os_prio=0 tid=0x00007ff5b8001000 nid=0x2f96 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
"Thread-0" #9 prio=5 os_prio=0 tid=0x00007ff6000ee000 nid=0x2e41 runnable [0x00007ff5ed46c000]
java.lang.Thread.State: RUNNABLE
at TestCPU100$MyThread.run(TestCPU100.java:6)
"Service Thread" #8 daemon prio=9 os_prio=0 tid=0x00007ff6000ca800 nid=0x2e3f runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
"C1 CompilerThread2" #7 daemon prio=9 os_prio=0 tid=0x00007ff6000bf800 nid=0x2e3e waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
"C2 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007ff6000bd800 nid=0x2e3d waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
"C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007ff6000ba800 nid=0x2e3c waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
"Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007ff6000b9000 nid=0x2e3b runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
"Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007ff600086000 nid=0x2e3a in Object.wait() [0x00007ff5edb73000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x000000076c708ee0> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144)
- locked <0x000000076c708ee0> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216)
"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007ff600081800 nid=0x2e39 in Object.wait() [0x00007ff5edc74000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x000000076c706c00> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:502)
at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
- locked <0x000000076c706c00> (a java.lang.ref.Reference$Lock)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
"main" #1 prio=5 os_prio=0 tid=0x00007ff600009800 nid=0x2e33 waiting on condition [0x00007ff606e01000]
java.lang.Thread.State: TIMED_WAITING (sleeping)
at java.lang.Thread.sleep(Native Method)
at TestCPU100.main(TestCPU100.java:12)
"VM Thread" os_prio=0 tid=0x00007ff600078000 nid=0x2e38 runnable
"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007ff60001e800 nid=0x2e34 runnable
"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007ff600020800 nid=0x2e35 runnable
"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00007ff600022000 nid=0x2e36 runnable
"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00007ff600024000 nid=0x2e37 runnable
"VM Periodic Task Thread" os_prio=0 tid=0x00007ff6000cd800 nid=0x2e40 waiting on condition
JNI global references: 5
可以看到
"Thread-0" #9 prio=5 os_prio=0 tid=0x00007ff6000ee000 nid=0x2e41 runnable [0x00007ff5ed46c000]
java.lang.Thread.State: RUNNABLE
at TestCPU100$MyThread.run(TestCPU100.java:6)
prio os_prio tid nid 啥意思
- prio java线程的优先级
- os_prio os线程的优先级
- tid java线程的id
- nid os线程的id
标签：lang,java,prio,0.0,100%,20,root,CPU 来源： https://blog.csdn.net/xiaolixi199311/article/details/114170284