linux-kernel - Re: [PATCH v2] perf pmu: Use available core PMU for raw events

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Message-ID: <CAP-5=fWE=jquq9WqReAu+Mow4r6LPgOOvxEXb-L5vK+UwThjGw@mail.gmail.com>
Date: Thu, 8 May 2025 08:11:03 -0700
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Kan Liang <kan.liang@...ux.intel.com>, 
	Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, 
	LKML <linux-kernel@...r.kernel.org>, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2] perf pmu: Use available core PMU for raw events

On Wed, May 7, 2025 at 2:59 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> When it finds a matching pmu for a legacy event, it should look for
> core pmus.  The raw events also refers to core events so it should be
> handled similarly.
>
> On x86, PERF_TYPE_RAW should match with the existing cpu PMU.  But on
> ARM, there's no PMU with the matching type so it'll pick the first core
> PMU for it.
>
> Suggested-by: Ian Rogers <irogers@...gle.com>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>

Reviewed-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/util/pmus.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
> index b99292de76693dbb..3bbd26fec78a10e2 100644
> --- a/tools/perf/util/pmus.c
> +++ b/tools/perf/util/pmus.c
> @@ -727,14 +727,21 @@ struct perf_pmu *evsel__find_pmu(const struct evsel *evsel)
>         legacy_core_type =
>                 evsel->core.attr.type == PERF_TYPE_HARDWARE ||
>                 evsel->core.attr.type == PERF_TYPE_HW_CACHE;
> -       if (!pmu && legacy_core_type) {
> -               if (perf_pmus__supports_extended_type()) {
> -                       u32 type = evsel->core.attr.config >> PERF_PMU_TYPE_SHIFT;
> +       if (!pmu && legacy_core_type && perf_pmus__supports_extended_type()) {
> +               u32 type = evsel->core.attr.config >> PERF_PMU_TYPE_SHIFT;
>
> -                       pmu = perf_pmus__find_by_type(type);
> -               } else {
> -                       pmu = perf_pmus__find_core_pmu();
> -               }
> +               pmu = perf_pmus__find_by_type(type);
> +       }
> +       if (!pmu && (legacy_core_type || evsel->core.attr.type == PERF_TYPE_RAW)) {
> +               /*
> +                * For legacy events, if there was no extended type info then
> +                * assume the PMU is the first core PMU.
> +                *
> +                * On architectures like ARM there is no sysfs PMU with type
> +                * PERF_TYPE_RAW, assume the RAW events are going to be handled
> +                * by the first core PMU.
> +                */
> +               pmu = perf_pmus__find_core_pmu();
>         }
>         ((struct evsel *)evsel)->pmu = pmu;
>         return pmu;
> --
> 2.49.0.987.g0cc8ee98dc-goog
>