linux-kernel - [PATCH v1] perf stat: Avoid merging/aggregating metric counts twice

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Date:   Wed,  8 Feb 2023 22:44:47 -0800
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        James Clark <james.clark@....com>,
        Eduard Zingerman <eddyz87@...il.com>,
        Florian Fischer <florian.fischer@...q.space>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Stephane Eranian <eranian@...gle.com>,
        Perry Taylor <perry.taylor@...el.com>
Subject: [PATCH v1] perf stat: Avoid merging/aggregating metric counts twice

The added perf_stat_merge_counters combines uncore counters. When
metrics are enabled, the counts are merged into a metric_leader
via the stat-shadow saved_value logic. As the leader now is
passed an aggregated count, it leads to all counters being added
together twice and counts appearing approximately doubled in
metrics.

This change disables the saved_value merging of counts for evsels
that are merged. It is recommended that later changes remove the
saved_value entirely as the two layers of aggregation in the code
is confusing.

Fixes: 942c5593393d ("perf stat: Add perf_stat_merge_counters()")
Reported-by: Perry Taylor <perry.taylor@...el.com>
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/stat-shadow.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
index cadb2df23c87..4cd05d9205e3 100644
--- a/tools/perf/util/stat-shadow.c
+++ b/tools/perf/util/stat-shadow.c
@@ -311,7 +311,7 @@ void perf_stat__update_shadow_stats(struct evsel *counter, u64 count,
 		update_stats(&v->stats, count);
 		if (counter->metric_leader)
 			v->metric_total += count;
-	} else if (counter->metric_leader) {
+	} else if (counter->metric_leader && !counter->merged_stat) {
 		v = saved_value_lookup(counter->metric_leader,
 				       map_idx, true, STAT_NONE, 0, st, rsd.cgrp);
 		v->metric_total += count;
-- 
2.39.1.519.gcb327c4b5f-goog