perf tools: Add a helper function to probe whether cpu-wide tracing is possible

Add a helper function to probe whether cpu-wide tracing is possible.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1439458857-30636-2-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 25 insertions, 0 deletions

diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 397757063da1..436e358300b1 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -115,6 +115,7 @@ void perf_evlist__close(struct perf_evlist *evlist);
 void perf_evlist__set_id_pos(struct perf_evlist *evlist);
 bool perf_can_sample_identifier(void);
 bool perf_can_record_switch_events(void);
+bool perf_can_record_cpu_wide(void);
 void perf_evlist__config(struct perf_evlist *evlist, struct record_opts *opts);
 int record_opts__config(struct record_opts *opts);
 
diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c
index 0d228a29526d..0467367dc315 100644
--- a/tools/perf/util/record.c
+++ b/tools/perf/util/record.c
@@ -105,6 +105,30 @@ bool perf_can_record_switch_events(void)
         return perf_probe_api(perf_probe_context_switch);
 }
 
+bool perf_can_record_cpu_wide(void)
+{
+        struct perf_event_attr attr = {
+                .type = PERF_TYPE_SOFTWARE,
+                .config = PERF_COUNT_SW_CPU_CLOCK,
+                .exclude_kernel = 1,
+        };
+        struct cpu_map *cpus;
+        int cpu, fd;
+
+        cpus = cpu_map__new(NULL);
+        if (!cpus)
+                return false;
+        cpu = cpus->map[0];
+        cpu_map__put(cpus);
+
+        fd = sys_perf_event_open(&attr, -1, cpu, -1, 0);
+        if (fd < 0)
+                return false;
+        close(fd);
+
+        return true;
+}
+
 void perf_evlist__config(struct perf_evlist *evlist, struct record_opts *opts)
 {
         struct perf_evsel *evsel;