linux-kernel - [PATCH 1/2] perf tools: Add a helper function to probe whether cpu-wide tracing is possible

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Date:	Thu, 13 Aug 2015 12:40:56 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>
Subject: [PATCH 1/2] 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@...el.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 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;
-- 
1.9.1

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