[PATCH v2 4/5] perf stat: Don't merge counters purely on name

Ian Rogers
2025-01-23T07:47:12Z

Counter merging was added in commit 942c5593393d ("perf stat: Add
perf_stat_merge_counters()"), however, it merges events with the same
name on different PMUs regardless of whether the different PMUs are
actually of the same type (ie they differ only in the suffix on the
PMU). For hwmon events there may be a temp1 event on every PMU, but
the PMU names are all unique and don't differ just by a suffix. The
merging is over eager and will merge all the hwmon counters together
meaning an aggregated and very large temp1 value is shown. The same
would be true for say cache events and memory controller events where
the PMUs differ but the event names are the same.

Fix the problem by correctly saying two PMUs alias when they differ
only by suffix.

Note, there is an overlap with evsel's merged_stat with aggregation
and the evsel's metric_leader where aggregation happens for metrics.

Fixes: 942c5593393d ("perf stat: Add perf_stat_merge_counters()")
Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/util/stat.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
index 7c2ccdcc3fdb..1f7abd8754c7 100644
--- a/tools/perf/util/stat.c
+++ b/tools/perf/util/stat.c
@@ -535,7 +535,10 @@ static int evsel__merge_aggr_counters(struct evsel *evsel, struct evsel *alias)

return 0;
}
-/* events should have the same name, scale, unit, cgroup but on different PMUs */
+/*
+ * Events should have the same name, scale, unit, cgroup but on different core
+ * PMUs or on different but matching uncore PMUs.
+ */
static bool evsel__is_alias(struct evsel *evsel_a, struct evsel *evsel_b)
{
if (strcmp(evsel__name(evsel_a), evsel__name(evsel_b)))
@@ -553,7 +556,13 @@ static bool evsel__is_alias(struct evsel *evsel_a, struct evsel *evsel_b)
if (evsel__is_clock(evsel_a) != evsel__is_clock(evsel_b))
return false;

- return evsel_a->pmu != evsel_b->pmu;
+ if (evsel_a->pmu == evsel_b->pmu || evsel_a->pmu == NULL || evsel_b->pmu == NULL)
+ return false;
+
+ if (evsel_a->pmu->is_core)
+ return evsel_b->pmu->is_core;
+
+ return perf_pmu__name_no_suffix_match(evsel_a->pmu, evsel_b->pmu->name);
}

static void evsel__merge_aliases(struct evsel *evsel)
--
2.48.1.262.g85cc9f2d1e-goog