效能調優 jstack

1. qmq是部署在tomcat中的應用名
   ps -ef | grep qmq | grep -v grep

拿到程式號， 例如上面對應的是3192

1. 第二步找出該程式內最耗費CPU的執行緒，可以使用ps -Lfp pid或者ps -mp pid -o THREAD, tid, time或者top -Hp pid
   例如用第三個 top -Hp 3192

Tasks: 123 total, 0 running, 123 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.3%us, 0.4%sy, 0.0%ni, 99.3%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 3922688k total, 3272588k used, 650100k free, 432768k buffers
Swap: 4194296k total, 0k used, 4194296k free, 596488k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3494 tomcat 20 0 4905m 1.1g 11m S 0.3 28.4 0:51.91 java
3551 tomcat 20 0 4905m 1.1g 11m S 0.3 28.4 4:46.32 java
3588 tomcat 20 0 4905m 1.1g 11m S 0.3 28.4 0:07.35 java
3192 tomcat 20 0 4905m 1.1g 11m S 0.0 28.4 0:00.00 java
3194 tomcat 20 0 4905m 1.1g 11m S 0.0 28.4 0:00.82 java

1. TIME列就是各個Java執行緒耗費的CPU時間，CPU時間最長的是執行緒ID為3551的執行緒，用
   printf “%x\n” 3551
   得到ddf

2. sudo -u tomcat jstack 3192 | grep ddf

“New I/O worker #30” daemon prio=10 tid=0x00007f44fd525800 nid=0xde4 runnable [0x00007f4530ddf000]
“DubboResponseTimeoutScanTimer” daemon prio=10 tid=0x00007f44fca88000 nid=0xddf waiting on condition [0x00007f45322e5000]