# 查看进程运行时间及上下文切换次数
Date: 2019-07-20


# 运行环境：

```
CentOS Linux release 7.5.1804 (Core)Linux centosgpt 5.2.0-rc4 #1 SMP Sun Jun 16 13:25:49 CST 2019 x86_64 x86_64 x86_64 GNU/Linux
```

# 进程的运行时间：

- ## 通过ps 查看
    

```
[root@centosgpt ~]# ps -o etime= -p "$$"
55:12

其中"$$"可以替换成具体的进程id， etime后的等号

man ps

-o format

...

If all column headers are empty (ps -o pid= -o comm=) then the header line will not be output.

...
```

* * *

# 上下文切换次数：

- ## 通过proc文件
    

          /proc/{pid}/status

```
[root@centosgpt ~]# grep ctxt /proc/1177/status
voluntary_ctxt_switches: 248
nonvoluntary_ctxt_switches: 2

volutary_ctxt_switches : 表示主动调度；
发生场景 等待IO或资源 调用__schedule,主动让出cpu
nonvolutary_ctxt_switches : 表示抢占式调度,；
发生场景：1时间片用完了， 需要切换到其他进程； 2 发生在高优先级进程被唤醒。
```

- ## 通过sysstat
    

        前提：安装sysstat：

        方法：yum install sysstat  （ubuntu 使用apt-get install sysstat）

        1.   可以查看所有进程的上下文切换情况（(kernels 2.6.23 and later only）

```
[root@centosgpt ~]# pidstat -w 1
Linux 5.2.0-rc4 (centosgpt)     07/20/2019      _x86_64_        (2 CPU)

07:55:59 PM   UID       PID   cswch/s nvcswch/s  Command
07:56:00 PM     0         9      1.94      0.00  ksoftirqd/0
07:56:00 PM     0        10     25.24      0.00  rcu_sched
07:56:00 PM     0       431      4.85      0.00  irq/16-vmwgfx
07:56:00 PM     0       944     10.68      0.00  vmtoolsd
07:56:00 PM     0       945      0.97      0.00  irqbalance
07:56:00 PM     0     38762      9.71      0.00  kworker/1:2-events_power_efficient
07:56:00 PM     0     38775     15.53      0.00  kworker/0:0-mm_percpu_wq
07:56:00 PM     0     38853    420.39      0.00  tar
07:56:00 PM     0     38854      0.97     15.53  gzip
07:56:00 PM     0     38858      0.97      1.94  pidstat
```

       2.   也可以查看指定进程下所有线程的上下文切换情况

```
[root@centosgpt ~]# pidstat -w -I -t -p 1177 3
Linux 5.2.0-rc4 (centosgpt)     07/20/2019      _x86_64_        (2 CPU)

08:02:06 PM   UID      TGID       TID   cswch/s nvcswch/s  Command
08:02:09 PM     0      1177         - 0.00      0.00  rsyslogd
08:02:09 PM     0         - 1177      0.00      0.00  |__rsyslogd
08:02:09 PM     0         - 1195      1.00      0.00  |__in:imjournal
08:02:09 PM     0         - 1196      0.00      0.00  |__rs:main
```

* * *

# 参考：

[How to check how long a process has been running?](https://unix.stackexchange.com/questions/7870/how-to-check-how-long-a-process-has-been-running)

[How to see how many context switches a process makes?](https://unix.stackexchange.com/questions/39342/how-to-see-how-many-context-switches-a-process-makes)

[进程切换：自愿(VOLUNTARY)与强制(INVOLUNTARY)](http://linuxperf.com/?p=209)

[How to see the sum of all context switches of all threads within a Java process?](https://stackoverflow.com/questions/21850505/how-to-see-the-sum-of-all-context-switches-of-all-threads-within-a-java-process)