This source file includes following definitions.
- smt_on
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/core_cpus", cpu);
27 if (access(fn, F_OK) == -1) {
28 snprintf(fn, sizeof fn,
29 "devices/system/cpu/cpu%d/topology/thread_siblings",
30 cpu);
31 }
32 if (sysfs__read_str(fn, &str, &strlen) < 0)
33 continue;
34
35 siblings = strtoull(str, NULL, 16);
36 free(str);
37 if (hweight64(siblings) > 1) {
38 cached_result = 1;
39 cached = true;
40 break;
41 }
42 }
43 if (!cached) {
44 cached_result = 0;
45 cached = true;
46 }
47 return cached_result;
48 }