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

[Ian Rogers]

On Thu, Apr 30, 2026 at 9:17 AM Ian Rogers <irogers@xxxxxxxxxx> 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@xxxxxxxxxx>

This passes Sashiko review (green). I didn't copy James Clark's
reviewed-by tag given the metricgroup code rewrite to avoid the loop,
but I think this is ready to land.

Thanks,
Ian

> ---
>  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);
>
> --
> 2.54.0.545.g6539524ca2-goog
>