C++ 如何从 C 中通过 PID 在 Linux 中计算进程的 CPU 使用率

您需要从/proc/<PID>/stat中解析出数据.以下是前几个字段(来自内核源代码中的Documentation/filesystems/proc.txt):

Table 1-3: Contents of the stat files (as of 2.6.22-rc3)
..............................................................................
 Field          Content
  pid           process id
  tcomm         filename of the executable
  state         state (R is running, S is sleeping, D is sleeping in an
                uninterruptible wait, Z is zombie, T is traced or stopped)
  ppid          process id of the parent process
  pgrp          pgrp of the process
  sid           session id
  tty_nr        tty the process uses
  tty_pgrp      pgrp of the tty
  flags         task flags
  min_flt       number of minor faults
  cmin_flt      number of minor faults with child's
  maj_flt       number of major faults
  cmaj_flt      number of major faults with child's
  utime         user mode jiffies
  stime         kernel mode jiffies
  cutime        user mode jiffies with child's
  cstime        kernel mode jiffies with child's

你可能已经过了utime岁和/或stime岁了.您还需要读取/proc/stat中的cpu行，如下所示:

cpu  192369 7119 480152 122044337 14142 9937 26747 0 0

它以Jiffie为单位告诉您在各种类别中使用的累计CPU时间.你需要把这条线上的值相加，才能得到time_total的测量值.

对于您感兴趣的流程，请同时阅读utime和stime，并从/proc/stat开始阅读time_total.然后睡上一秒钟左右，然后把它们再读一遍.现在，您可以使用以下命令计算采样时间内进程的CPU使用率:

user_util = 100 * (utime_after - utime_before) / (time_total_after - time_total_before);
sys_util = 100 * (stime_after - stime_before) / (time_total_after - time_total_before);

讲得通?