tools/perf/util/smt.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <unistd.h>
   4 #include <linux/bitops.h>
   5 #include "api/fs/fs.h"
   6 #include "smt.h"
   7
   8 /**
   9  * hweight_str - Returns the number of bits set in str. Stops at first non-hex
  10  *             or ',' character.
  11  */
  12 static int hweight_str(char *str)
  13 {
  14         int result = 0;
  15
  16         while (*str) {
  17                 switch (*str++) {
  18                 case '0':
  19                 case ',':
  20                         break;
  21                 case '1':
  22                 case '2':
  23                 case '4':
  24                 case '8':
  25                         result++;
  26                         break;
  27                 case '3':
  28                 case '5':
  29                 case '6':
  30                 case '9':
  31                 case 'a':
  32                 case 'A':
  33                 case 'c':
  34                 case 'C':
  35                         result += 2;
  36                         break;
  37                 case '7':
  38                 case 'b':
  39                 case 'B':
  40                 case 'd':
  41                 case 'D':
  42                 case 'e':
  43                 case 'E':
  44                         result += 3;
  45                         break;
  46                 case 'f':
  47                 case 'F':
  48                         result += 4;
  49                         break;
  50                 default:
  51                         goto done;
  52                 }
  53         }
  54 done:
  55         return result;
  56 }
  57
  58 int smt_on(void)
  59 {
  60         static bool cached;
  61         static int cached_result;
  62         int cpu;
  63         int ncpu;
  64
  65         if (cached)
  66                 return cached_result;
  67
  68         if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) >= 0) {
  69                 cached = true;
  70                 return cached_result;
  71         }
  72
  73         cached_result = 0;
  74         ncpu = sysconf(_SC_NPROCESSORS_CONF);
  75         for (cpu = 0; cpu < ncpu; cpu++) {
  76                 unsigned long long siblings;
  77                 char *str;
  78                 size_t strlen;
  79                 char fn[256];
  80
  81                 snprintf(fn, sizeof fn,
  82                         "devices/system/cpu/cpu%d/topology/thread_siblings", cpu);
  83                 if (sysfs__read_str(fn, &str, &strlen) < 0) {
  84                         snprintf(fn, sizeof fn,
  85                                 "devices/system/cpu/cpu%d/topology/core_cpus", cpu);
  86                         if (sysfs__read_str(fn, &str, &strlen) < 0)
  87                                 continue;
  88                 }
  89                 /* Entry is hex, but does not have 0x, so need custom parser */
  90                 siblings = hweight_str(str);
  91                 free(str);
  92                 if (siblings > 1) {
  93                         cached_result = 1;
  94                         break;
  95                 }
  96         }
  97         cached = true;
  98         return cached_result;
  99 }