Re: [PATCH v1] perf metricgroup: Avoid scanning unnecessary PMUs for identifier match

[Namhyung Kim <namhyung@kernel.org>]

On Mon, Mar 30, 2026 at 03:44:21PM +0100, James Clark wrote:
> 
> 
> On 26/03/2026 10:44 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>
> 
> Reviewed-by: James Clark <james.clark@linaro.org>
> 
> > ---
> >   tools/perf/util/metricgroup.c |  8 ++------
> >   tools/perf/util/pmus.c        | 18 +++++++++++++++++-
> >   tools/perf/util/pmus.h        |  1 +
> >   3 files changed, 20 insertions(+), 7 deletions(-)
> > 
> > diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> > index 7e39d469111b..769b38400832 100644
> > --- a/tools/perf/util/metricgroup.c
> > +++ b/tools/perf/util/metricgroup.c
> > @@ -410,13 +410,9 @@ 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;
> > -
> > +	while ((pmu = perf_pmus__scan_for_uncore_id(pmu, pm->compat)))
> >   		return d->fn(pm, table, d->data);

Sashiko review: it's natural to convert it to 'if'.

Thanks,
Namhyung


> > -	}
> > +
> >   	return 0;
> >   }
> > diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
> > index 98be2eb8f1f0..9859d7056fb7 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);
>