GNU Linux-libre 4.19.211-gnu1
[releases.git] / 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 int smt_on(void)
9 {
10         static bool cached;
11         static int cached_result;
12         int cpu;
13         int ncpu;
14
15         if (cached)
16                 return cached_result;
17
18         ncpu = sysconf(_SC_NPROCESSORS_CONF);
19         for (cpu = 0; cpu < ncpu; cpu++) {
20                 unsigned long long siblings;
21                 char *str;
22                 size_t strlen;
23                 char fn[256];
24
25                 snprintf(fn, sizeof fn,
26                         "devices/system/cpu/cpu%d/topology/thread_siblings",
27                         cpu);
28                 if (sysfs__read_str(fn, &str, &strlen) < 0)
29                         continue;
30                 /* Entry is hex, but does not have 0x, so need custom parser */
31                 siblings = strtoull(str, NULL, 16);
32                 free(str);
33                 if (hweight64(siblings) > 1) {
34                         cached_result = 1;
35                         cached = true;
36                         break;
37                 }
38         }
39         if (!cached) {
40                 cached_result = 0;
41                 cached = true;
42         }
43         return cached_result;
44 }