Commit c9d699e1 authored by James Clark's avatar James Clark Committed by Namhyung Kim
Browse files

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: d9c5f5f9 ("perf pmu: Count sys and cpuid JSON events separately")
Reviewed-by: default avatarIan Rogers <irogers@google.com>
Signed-off-by: default avatarJames Clark <james.clark@linaro.org>
Link: https://lore.kernel.org/r/20250226104111.564443-3-james.clark@linaro.org


Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
parent 72c6f57a

tools/perf/util/pmu.c

+4 −3
Original line number Diff line number Diff line
@@ -595,7 +595,7 @@ 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;
@@ -1880,9 +1880,10 @@ 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();

tools/perf/util/pmu.h

+5 −0
Original line number Diff line number Diff line
@@ -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;

	/**