linux-kernel - [PATCH v2 2/3] perf pmu: Don't double count common sysfs and json events

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Message-Id: <20250226104111.564443-3-james.clark@linaro.org>
Date: Wed, 26 Feb 2025 10:41:01 +0000
From: James Clark <james.clark@...aro.org>
To: linux-perf-users@...r.kernel.org,
	irogers@...gle.com,
	namhyung@...nel.org,
	cyy@...self.name
Cc: James Clark <james.clark@...aro.org>,
	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>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Weilin Wang <weilin.wang@...el.com>,
	Yoshihiro Furudera <fj5100bi@...itsu.com>,
	Jean-Philippe Romain <jean-philippe.romain@...s.st.com>,
	Junhao He <hejunhao3@...wei.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/3] perf pmu: Don't double count common sysfs and json events

After pmu_add_cpu_aliases() is called, perf_pmu__num_events() returns an
incorrect value that double counts common events and doesn't match the
actual count of events in the alias list. This is because after
'cpu_aliases_added == true', the number of events returned is
'sysfs_aliases + cpu_json_aliases'. But when adding 'case
EVENT_SRC_SYSFS' events, 'sysfs_aliases' and 'cpu_json_aliases' are both
incremented together, failing to account that these ones overlap and
only add a single item to the list. Fix it by adding another counter for
overlapping events which doesn't influence 'cpu_json_aliases'.

There doesn't seem to be a current issue because it's used in perf list
before pmu_add_cpu_aliases() so the correct value is returned. Other
uses in tests may also miss it for other reasons like only looking at
uncore events. However it's marked as a fixes commit in case any new fix
with new uses of perf_pmu__num_events() is backported.

Fixes: d9c5f5f94c2d ("perf pmu: Count sys and cpuid JSON events separately")
Reviewed-by: Ian Rogers <irogers@...gle.com>
Signed-off-by: James Clark <james.clark@...aro.org>
---
 tools/perf/util/pmu.c | 7 ++++---
 tools/perf/util/pmu.h | 5 +++++
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index ec3878c890a9..72aa6167c090 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -596,7 +596,7 @@ static int perf_pmu__new_alias(struct perf_pmu *pmu, const char *name,
 			};
 			if (pmu_events_table__find_event(pmu->events_table, pmu, name,
 							 update_alias, &data) == 0)
-				pmu->cpu_json_aliases++;
+				pmu->cpu_common_json_aliases++;
 		}
 		pmu->sysfs_aliases++;
 		break;
@@ -1884,9 +1884,10 @@ size_t perf_pmu__num_events(struct perf_pmu *pmu)
 	if (pmu->cpu_aliases_added)
 		 nr += pmu->cpu_json_aliases;
 	else if (pmu->events_table)
-		nr += pmu_events_table__num_events(pmu->events_table, pmu) - pmu->cpu_json_aliases;
+		nr += pmu_events_table__num_events(pmu->events_table, pmu) -
+			pmu->cpu_common_json_aliases;
 	else
-		assert(pmu->cpu_json_aliases == 0);
+		assert(pmu->cpu_json_aliases == 0 && pmu->cpu_common_json_aliases == 0);
 
 	if (perf_pmu__is_tool(pmu))
 		nr -= tool_pmu__num_skip_events();
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index f5306428c03f..b93014cc3670 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -136,6 +136,11 @@ struct perf_pmu {
 	uint32_t cpu_json_aliases;
 	/** @sys_json_aliases: Number of json event aliases loaded matching the PMU's identifier. */
 	uint32_t sys_json_aliases;
+	/**
+	 * @cpu_common_json_aliases: Number of json events that overlapped with sysfs when
+	 * loading all sysfs events.
+	 */
+	uint32_t cpu_common_json_aliases;
 	/** @sysfs_aliases_loaded: Are sysfs aliases loaded from disk? */
 	bool sysfs_aliases_loaded;
 	/**
-- 
2.34.1