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author | Andi Kleen <ak@linux.intel.com> | 2017-08-11 16:26:22 -0700 |
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committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2017-08-22 12:09:04 -0300 |
commit | de5077c4e38f2a51f50d28bdd5e4a0f14b3d16ff (patch) | |
tree | 95de3aa45603112fa658a9b12f9e2e591bec57e9 /tools/perf/util/smt.c | |
parent | 77d0871c76bad1093a3d86870fe76dd1ad0ca397 (diff) | |
download | op-kernel-dev-de5077c4e38f2a51f50d28bdd5e4a0f14b3d16ff.zip op-kernel-dev-de5077c4e38f2a51f50d28bdd5e4a0f14b3d16ff.tar.gz |
perf tools: Add utility function to detect SMT status
Add an smt_on() function to return if SMT is enabled or disabled. Used
in the next patch.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/20170811232634.30465-7-andi@firstfloor.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/util/smt.c')
-rw-r--r-- | tools/perf/util/smt.c | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c new file mode 100644 index 0000000..453f6f6 --- /dev/null +++ b/tools/perf/util/smt.c @@ -0,0 +1,44 @@ +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> +#include <linux/bitops.h> +#include "api/fs/fs.h" +#include "smt.h" + +int smt_on(void) +{ + static bool cached; + static int cached_result; + int cpu; + int ncpu; + + if (cached) + return cached_result; + + ncpu = sysconf(_SC_NPROCESSORS_CONF); + for (cpu = 0; cpu < ncpu; cpu++) { + unsigned long long siblings; + char *str; + size_t strlen; + char fn[256]; + + snprintf(fn, sizeof fn, + "devices/system/cpu/cpu%d/topology/thread_siblings", + cpu); + if (sysfs__read_str(fn, &str, &strlen) < 0) + continue; + /* Entry is hex, but does not have 0x, so need custom parser */ + siblings = strtoull(str, NULL, 16); + free(str); + if (hweight64(siblings) > 1) { + cached_result = 1; + cached = true; + break; + } + } + if (!cached) { + cached_result = 0; + cached = true; + } + return cached_result; +} |