[PATCH v2 07/19] perf, tools: Add utility function to detect SMT status

Andi Kleen
2017-08-11T23:28:49Z

From: Andi Kleen <ak@linux.intel.com>

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>
---
tools/perf/util/Build | 1 +
tools/perf/util/smt.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/smt.h | 6 ++++++
3 files changed, 51 insertions(+)
create mode 100644 tools/perf/util/smt.c
create mode 100644 tools/perf/util/smt.h

diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index 8d49a989f193..94518c1bf8b6 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -22,6 +22,7 @@ libperf-y += rbtree.o
libperf-y += libstring.o
libperf-y += bitmap.o
libperf-y += hweight.o
+libperf-y += smt.o
libperf-y += quote.o
libperf-y += strbuf.o
libperf-y += string.o
diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
new file mode 100644
index 000000000000..453f6f6f29f3
--- /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;
+}
diff --git a/tools/perf/util/smt.h b/tools/perf/util/smt.h
new file mode 100644
index 000000000000..b8414b7bcbc8
--- /dev/null
+++ b/tools/perf/util/smt.h
@@ -0,0 +1,6 @@
+#ifndef SMT_H
+#define SMT_H 1
+
+int smt_on(void);
+
+#endif
--
2.9.4