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From: Namhyung Kim <namhyung@kernel.org>
To: Arnaldo Carvalho de Melo <acme@kernel.org>, Jiri Olsa <jolsa@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Stephane Eranian <eranian@google.com>,
	Ian Rogers <irogers@google.com>, Sam Xi <xyzsam@google.com>,
	Andi Kleen <ak@linux.intel.com>
Subject: [PATCH v2 1/2] perf stat: Use proper cpu for shadow stats
Date: Fri, 27 Nov 2020 13:14:03 +0900
Message-ID: <20201127041404.390276-1-namhyung@kernel.org> (raw)

Currently perf stat shows some metrics (like IPC) for defined events.
But when no aggregation mode is used (-A option), it shows incorrect
values since it used a value from a different cpu.

Before:

  $ perf stat -aA -e cycles,instructions sleep 1

   Performance counter stats for 'system wide':

  CPU0      116,057,380      cycles
  CPU1       86,084,722      cycles
  CPU2       99,423,125      cycles
  CPU3       98,272,994      cycles
  CPU0       53,369,217      instructions      #    0.46  insn per cycle
  CPU1       33,378,058      instructions      #    0.29  insn per cycle
  CPU2       58,150,086      instructions      #    0.50  insn per cycle
  CPU3       40,029,703      instructions      #    0.34  insn per cycle

       1.001816971 seconds time elapsed

So the IPC for CPU1 should be 0.38 (= 33,378,058 / 86,084,722)
but it was 0.29 (= 33,378,058 / 116,057,380) and so on.

After:

  $ perf stat -aA -e cycles,instructions sleep 1

   Performance counter stats for 'system wide':

  CPU0      109,621,384      cycles
  CPU1      159,026,454      cycles
  CPU2       99,460,366      cycles
  CPU3      124,144,142      cycles
  CPU0       44,396,706      instructions      #    0.41  insn per cycle
  CPU1      120,195,425      instructions      #    0.76  insn per cycle
  CPU2       44,763,978      instructions      #    0.45  insn per cycle
  CPU3       69,049,079      instructions      #    0.56  insn per cycle

       1.001910444 seconds time elapsed

Reported-by: Sam Xi <xyzsam@google.com>
Fixes: 44d49a600259 ("perf stat: Support metrics in --per-core/socket mode")
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/stat-display.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
index 4b57c0c07632..a963b5b8eb72 100644
--- a/tools/perf/util/stat-display.c
+++ b/tools/perf/util/stat-display.c
@@ -324,13 +324,10 @@ static int first_shadow_cpu(struct perf_stat_config *config,
 	struct evlist *evlist = evsel->evlist;
 	int i;
 
-	if (!config->aggr_get_id)
-		return 0;
-
 	if (config->aggr_mode == AGGR_NONE)
 		return id;
 
-	if (config->aggr_mode == AGGR_GLOBAL)
+	if (!config->aggr_get_id)
 		return 0;
 
 	for (i = 0; i < evsel__nr_cpus(evsel); i++) {
-- 
2.29.2.454.gaff20da3a2-goog


             reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-27  4:14 Namhyung Kim [this message]
2020-11-27  4:14 ` [PATCH v2 2/2] perf test: Add shadow stat test Namhyung Kim
2020-11-30 11:59   ` Arnaldo Carvalho de Melo
2020-11-27 17:32 ` [PATCH v2 1/2] perf stat: Use proper cpu for shadow stats Arnaldo Carvalho de Melo

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