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
smt_on(void)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 if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) >= 0)
19 goto done;
20
21 ncpu = sysconf(_SC_NPROCESSORS_CONF);
22 for (cpu = 0; cpu < ncpu; cpu++) {
23 unsigned long long siblings;
24 char *str;
25 size_t strlen;
26 char fn[256];
27
28 snprintf(fn, sizeof fn,
29 "devices/system/cpu/cpu%d/topology/core_cpus", cpu);
30 if (sysfs__read_str(fn, &str, &strlen) < 0) {
31 snprintf(fn, sizeof fn,
32 "devices/system/cpu/cpu%d/topology/thread_siblings",
33 cpu);
34 if (sysfs__read_str(fn, &str, &strlen) < 0)
35 continue;
36 }
37 /* Entry is hex, but does not have 0x, so need custom parser */
38 siblings = strtoull(str, NULL, 16);
39 free(str);
40 if (hweight64(siblings) > 1) {
41 cached_result = 1;
42 cached = true;
43 break;
44 }
45 }
46 if (!cached) {
47 cached_result = 0;
48 done:
49 cached = true;
50 }
51 return cached_result;
52 }
53