查看某个进程的PID
如查看java的进程的pid，ps -ef | grep java:
[root@localhost ~]# ps -ef | grep java
root 124146 1984 0 09:13 pts/0 00:00:06 java -jar arthas-demo.jar
root 125210 98378 0 10:07 pts/1 00:00:00 grep --color=auto java
查看特定进程的数量
如查看java进程的数量,ps -ef | grep java| wc -l：
[root@localhost ~]# ps -ef | grep java| wc -l
2
查看线程是否存在死锁
查看线程是否存在死锁，jstack -l pid：
[root@localhost ~]# jstack -l 124146
2020-05-02 10:13:38
Full thread dump OpenJDK 64-Bit Server VM (25.252-b09 mixed mode):
"C1 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007f27f013c000 nid=0x1e4f9 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007f27f012d000 nid=0x1e4f8 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"main" #1 prio=5 os_prio=0 tid=0x00007f27f004b800 nid=0x1e4f3 waiting on condition [0x00007f27f7274000]
java.lang.Thread.State: TIMED_WAITING (sleeping)
at java.lang.Thread.sleep(Native Method)
at java.lang.Thread.sleep(Thread.java:340)
at java.util.concurrent.TimeUnit.sleep(TimeUnit.java:386)
at demo.MathGame.main(MathGame.java:17)
Locked ownable synchronizers:
- None
...
查看某个进程的线程数
ps -efL | grep [PID] | wc -l，如：
[root@localhost ~]# ps -efL | grep 124146 | wc -l
12
查看具体有哪些线程用ps -Lp [pid] cu:
[root@localhost ~]# ps -Lp 124146 cu
USER PID LWP %CPU NLWP %MEM VSZ RSS TTY STAT START TIME COMMAND
root 124146 124146 0.0 11 2.5 2489116 35724 pts/0 Sl+ 09:13 0:00 java
root 124146 124147 0.0 11 2.5 2489116 35724 pts/0 Sl+ 09:13 0:01 java
root 124146 124148 0.0 11 2.5 2489116 35724 pts/0 Sl+ 09:13 0:00 VM Thread
root 124146 124149 0.0 11 2.5 2489116 35724 pts/0 Sl+ 09:13 0:00 Reference Handl
root 124146 124150 0.0 11 2.5 2489116 35724 pts/0 Sl+ 09:13 0:00 Finalizer
root 124146 124151 0.0 11 2.5 2489116 35724 pts/0 Sl+ 09:13 0:00 Signal Dispatch
root 124146 124152 0.0 11 2.5 2489116 35724 pts/0 Sl+ 09:13 0:00 C2 CompilerThre
root 124146 124153 0.0 11 2.5 2489116 35724 pts/0 Sl+ 09:13 0:00 C1 CompilerThre
root 124146 124154 0.0 11 2.5 2489116 35724 pts/0 Sl+ 09:13 0:00 Service Thread
root 124146 124155 0.1 11 2.5 2489116 35724 pts/0 Sl+ 09:13 0:05 VM Periodic Tas
root 124146 125362 0.0 11 2.5 2489116 35724 pts/0 Sl+ 10:13 0:00 Attach Listener
统计所有的log文件中，包含Error字符的行
find / -type f -name "*.log" | xargs grep "ERROR"，这个在排查问题过程中比较有用：
[root@localhost ~]# find / -type f -name "*.log" | xargs grep "ERROR"
/var/log/tuned/tuned.log:2020-03-13 18:05:59,145 ERROR tuned.utils.commands: Writing to file '/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor' error: '[Errno 19] No such device'
/var/log/tuned/tuned.log:2020-03-13 18:05:59,145 ERROR tuned.utils.commands: Writing to file '/sys/devices/system/cpu/cpu1/cpufreq/scaling_governor' error: '[Errno 19] No such device'
/var/log/tuned/tuned.log:2020-04-28 14:55:34,857 ERROR tuned.utils.commands: Writing to file '/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor' error: '[Errno 19] No such device'
/var/log/tuned/tuned.log:2020-04-28 14:55:34,859 ERROR tuned.utils.commands: Writing to file '/sys/devices/system/cpu/cpu1/cpufreq/scaling_governor' error: '[Errno 19] No such device'
/var/log/tuned/tuned.log:2020-04-28 15:23:19,037 ERROR tuned.utils.commands: Writing to file '/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor' error: '[Errno 19] No such device'
...
应用启动时指定JVM参数
java -jar -Xms128m -Xmx1024m -Xss512k -XX:PermSize=128m -XX:MaxPermSize=64m -XX:NewSize=64m -XX:MaxNewSize=256m arthas-demo.jar，如：
[root@localhost ~]# java -jar -Xms128m -Xmx1024m -Xss512k -XX:PermSize=128m -XX:MaxPermSize=64m -XX:NewSize=64m -XX:MaxNewSize=256m arthas-demo.jar
OpenJDK 64-Bit Server VM warning: ignoring option PermSize=128m; support was removed in 8.0
OpenJDK 64-Bit Server VM warning: ignoring option MaxPermSize=64m; support was removed in 8.0
157518=2*3*3*3*2917
illegalArgumentCount: 1, number is: -187733, need >= 2
illegalArgumentCount: 2, number is: -102156, need >= 2
173379=3*57793