[tip:perf/core] perf tools: Add a helper function to probe whether cpu-wide tracing is possible

[tip-bot for Adrian Hunter <tipbot@zytor.com>]

Commit-ID:  835095653ebfe4b16596a30db1c4e7c414014b5e
Gitweb:     http://git.kernel.org/tip/835095653ebfe4b16596a30db1c4e7c414014b5e
Author:     Adrian Hunter <adrian.hunter@intel.com>
AuthorDate: Thu, 13 Aug 2015 12:40:56 +0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 17 Aug 2015 11:08:37 -0300

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>
---
 tools/perf/util/evlist.h |  1 +
 tools/perf/util/record.c | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 3977570..436e358 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 0d228a2..0467367 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;