linux-kernel - [PATCHv3] perf stat: Ensure group is defined on top of the same cpu mask

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Date:   Tue, 2 Jun 2020 12:17:36 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jin Yao <yao.jin@...ux.intel.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Michael Petlan <mpetlan@...hat.com>,
        Stephane Eranian <eranian@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: [PATCHv3] perf stat: Ensure group is defined on top of the same cpu
 mask

Jin Yao reported the issue (and posted first versions of this change)
with groups being defined over events with different cpu mask.

This causes assert aborts in get_group_fd, like:

  # perf stat -M "C2_Pkg_Residency" -a -- sleep 1
  perf: util/evsel.c:1464: get_group_fd: Assertion `!(fd == -1)' failed.
  Aborted

All the events in the group have to be defined over the same
cpus so the group_fd can be found for every leader/member pair.

Adding check to ensure this condition is met and removing the
group (with warning) if we detect mixed cpus, like:

  $ sudo perf stat -e '{power/energy-cores/,cycles},{instructions,power/energy-cores/}'
  WARNING: event cpu maps do not match, disabling group:
    anon group { power/energy-cores/, cycles }
    anon group { instructions, power/energy-cores/ }

Ian asked also for cpu maps details, it's displayed in verbose mode:

  $ sudo perf stat -e '{cycles,power/energy-cores/}' -v
  WARNING: group events cpu maps do not match, disabling group:
    anon group { power/energy-cores/, cycles }
       power/energy-cores/: 0
       cycles: 0-7
    anon group { instructions, power/energy-cores/ }
       instructions: 0-7
       power/energy-cores/: 0

Fixes: 6a4bb04caacc8 ("perf tools: Enable grouping logic for parsed events")
Co-developed-by: Jin Yao <yao.jin@...ux.intel.com>
Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/perf/builtin-stat.c | 55 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

 v3 changes:
   - reword the warning with Ian's suggestion

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index b2b79aa161dd..9be020e0098a 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -190,6 +190,59 @@ static struct perf_stat_config stat_config = {
 	.big_num		= true,
 };
 
+static bool cpus_map_matched(struct evsel *a, struct evsel *b)
+{
+	if (!a->core.cpus && !b->core.cpus)
+		return true;
+
+	if (!a->core.cpus || !b->core.cpus)
+		return false;
+
+	if (a->core.cpus->nr != b->core.cpus->nr)
+		return false;
+
+	for (int i = 0; i < a->core.cpus->nr; i++) {
+		if (a->core.cpus->map[i] != b->core.cpus->map[i])
+			return false;
+	}
+
+	return true;
+}
+
+static void evlist__check_cpu_maps(struct evlist *evlist)
+{
+	struct evsel *evsel, *pos, *leader;
+	char buf[1024];
+
+	evlist__for_each_entry(evlist, evsel) {
+		leader = evsel->leader;
+
+		/* Check that leader matches cpus with each member. */
+		if (leader == evsel)
+			continue;
+		if (cpus_map_matched(leader, evsel))
+			continue;
+
+		/* If there's mismatch disable the group and warn user. */
+		WARN_ONCE(1, "WARNING: grouped events cpus do not match, disabling group:\n");
+		evsel__group_desc(leader, buf, sizeof(buf));
+		pr_warning("  %s\n", buf);
+
+		if (verbose) {
+			cpu_map__snprint(leader->core.cpus, buf, sizeof(buf));
+			pr_warning("     %s: %s\n", leader->name, buf);
+			cpu_map__snprint(evsel->core.cpus, buf, sizeof(buf));
+			pr_warning("     %s: %s\n", evsel->name, buf);
+		}
+
+		for_each_group_evsel(pos, leader) {
+			pos->leader = pos;
+			pos->core.nr_members = 0;
+		}
+		evsel->leader->core.nr_members = 0;
+	}
+}
+
 static inline void diff_timespec(struct timespec *r, struct timespec *a,
 				 struct timespec *b)
 {
@@ -2113,6 +2166,8 @@ int cmd_stat(int argc, const char **argv)
 		goto out;
 	}
 
+	evlist__check_cpu_maps(evsel_list);
+
 	/*
 	 * Initialize thread_map with comm names,
 	 * so we could print it out on output.
-- 
2.25.4