release/src/router/busybox/libbb/get_cpu_count.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Factored out of mpstat/iostat.
   4  *
   5  * Copyright (C) 2010 Marek Polacek <mmpolacek@gmail.com>
   6  *
   7  * Licensed under GPLv2, see file LICENSE in this source tree.
   8  */
   9 #include "libbb.h"
  10
  11 /* Does str start with "cpu"? */
  12 int FAST_FUNC starts_with_cpu(const char *str)
  13 {
  14         return ((str[0] - 'c') | (str[1] - 'p') | (str[2] - 'u')) == 0;
  15 }
  16
  17 /*
  18  * Get number of processors. Uses /proc/stat.
  19  * Return value 0 means one CPU and non SMP kernel.
  20  * Otherwise N means N processor(s) and SMP kernel.
  21  */
  22 unsigned FAST_FUNC get_cpu_count(void)
  23 {
  24         FILE *fp;
  25         char line[256];
  26         int proc_nr = -1;
  27
  28         fp = xfopen_for_read("/proc/stat");
  29         while (fgets(line, sizeof(line), fp)) {
  30                 if (!starts_with_cpu(line)) {
  31                         if (proc_nr >= 0)
  32                                 break; /* we are past "cpuN..." lines */
  33                         continue;
  34                 }
  35                 if (line[3] != ' ') { /* "cpuN" */
  36                         int num_proc;
  37                         if (sscanf(line + 3, "%u", &num_proc) == 1
  38                          && num_proc > proc_nr
  39                         ) {
  40                                 proc_nr = num_proc;
  41                         }
  42                 }
  43         }
  44
  45         fclose(fp);
  46         return proc_nr + 1;
  47 }