Re: [PATCH v2] perf metricgroup: Avoid scanning unnecessary PMUs for identifier match

[James Clark <james.clark@linaro.org>]

On 30/04/2026 5:17 pm, Ian Rogers wrote:
> Only uncore PMUs can have an identifier, so add an optimized
> perf_pmus__scan routine for that case to avoid all PMU types being
> created.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>   tools/perf/util/metricgroup.c | 11 +++--------
>   tools/perf/util/pmus.c        | 18 +++++++++++++++++-
>   tools/perf/util/pmus.h        |  1 +
>   3 files changed, 21 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> index 4db9578efd81..5a489e97c413 100644
> --- a/tools/perf/util/metricgroup.c
> +++ b/tools/perf/util/metricgroup.c
> @@ -415,14 +415,9 @@ static int metricgroup__sys_event_iter(const struct pmu_metric *pm,
>   	if (!pm->metric_expr || !pm->compat)
>   		return 0;
>   
> -	while ((pmu = perf_pmus__scan(pmu))) {
> -
> -		if (!pmu->id || !pmu_uncore_identifier_match(pm->compat, pmu->id))
> -			continue;
> -
> -		return d->fn(pm, table, d->data);
> -	}
> -	return 0;
> +	/* Only process with the iterator if there is a a PMU that matches the ID. */
> +	pmu = perf_pmus__scan_for_uncore_id(pmu, pm->compat);
> +	return pmu ? d->fn(pm, table, d->data) : 0;
>   }
>   
>   int metricgroup__for_each_metric(const struct pmu_metrics_table *table, pmu_metric_iter_fn fn,
> diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
> index 9a2023ceeefd..5e3f571450fe 100644
> --- a/tools/perf/util/pmus.c
> +++ b/tools/perf/util/pmus.c
> @@ -409,7 +409,7 @@ struct perf_pmu *perf_pmus__scan_matching_wildcard(struct perf_pmu *pmu, const c
>   	if (!pmu) {
>   		/*
>   		 * Core PMUs, other sysfs PMUs and tool PMU can have any name or
> -		 * aren't wother optimizing for.
> +		 * aren't worth optimizing for.
>   		 */
>   		unsigned int to_read_pmus =  PERF_TOOL_PMU_TYPE_PE_CORE_MASK |
>   			PERF_TOOL_PMU_TYPE_PE_OTHER_MASK |
> @@ -486,6 +486,22 @@ static struct perf_pmu *perf_pmus__scan_skip_duplicates(struct perf_pmu *pmu)
>   	return NULL;
>   }
>   
> +struct perf_pmu *perf_pmus__scan_for_uncore_id(struct perf_pmu *pmu, const char *compat)
> +{
> +	if (!pmu) {
> +		/* Only uncore PMUs can have identifiers. */
> +		unsigned int to_read_pmus = PERF_TOOL_PMU_TYPE_PE_OTHER_MASK;
> +
> +		pmu_read_sysfs(to_read_pmus);
> +		pmu = list_prepare_entry(pmu, &other_pmus, list);
> +	}
> +	list_for_each_entry_continue(pmu, &other_pmus, list) {
> +		if (pmu->id && pmu_uncore_identifier_match(compat, pmu->id))
> +			return pmu;
> +	}
> +	return NULL;
> +}
> +
>   const struct perf_pmu *perf_pmus__pmu_for_pmu_filter(const char *str)
>   {
>   	struct perf_pmu *pmu = NULL;
> diff --git a/tools/perf/util/pmus.h b/tools/perf/util/pmus.h
> index 7cb36863711a..0d55edb3f2fc 100644
> --- a/tools/perf/util/pmus.h
> +++ b/tools/perf/util/pmus.h
> @@ -23,6 +23,7 @@ struct perf_pmu *perf_pmus__scan(struct perf_pmu *pmu);
>   struct perf_pmu *perf_pmus__scan_core(struct perf_pmu *pmu);
>   struct perf_pmu *perf_pmus__scan_for_event(struct perf_pmu *pmu, const char *event);
>   struct perf_pmu *perf_pmus__scan_matching_wildcard(struct perf_pmu *pmu, const char *wildcard);
> +struct perf_pmu *perf_pmus__scan_for_uncore_id(struct perf_pmu *pmu, const char *compat);
>   
>   const struct perf_pmu *perf_pmus__pmu_for_pmu_filter(const char *str);
>   

Reviewed-by: James Clark <james.clark@linaro.org>