linux-kernel - Re: [PATCH v1 02/10] perf parse-events filter: Use evsel__find

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Message-ID: <CAP-5=fVrB8hRc0-K6D001xBNr6M-xjYMOet+-tafei101achig@mail.gmail.com>
Date: Wed, 12 Feb 2025 08:11:12 -0800
From: Ian Rogers <irogers@...gle.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	Hao Ge <gehao@...inos.cn>, James Clark <james.clark@...aro.org>, 
	Howard Chu <howardchu95@...il.com>, Dominique Martinet <asmadeus@...ewreck.org>, 
	Levi Yun <yeoreum.yun@....com>, Xu Yang <xu.yang_2@....com>, 
	Tengda Wu <wutengda@...weicloud.com>, Yang Jihong <yangjihong1@...wei.com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 02/10] perf parse-events filter: Use evsel__find_pmu

On Wed, Feb 12, 2025 at 6:51 AM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> On Sat, Jan 11, 2025 at 11:01:35AM -0800, Ian Rogers wrote:
> > Rather than manually scanning PMUs, use evsel__find_pmu that can use
> > the PMU set during event parsing.
>
> Right, and then evsel__find_pmu() also does some extra checks to call
> pmu_read_sysfs() more selectively, right?

Right, but the pmu should already be initialized by parse_events so no
scanning should be necessary:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/pmus.c?h=perf-tools-next#n759
You are right that the fall back to perf_pmus__find_by_type is more
selective in what it scans:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/pmus.c?h=perf-tools-next#n302
First seeing if the PMU is already loaded then just loading the PMUs
relevant to the type number.

Thanks,
Ian

> - Arnaldo
>
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> >  tools/perf/util/parse-events.c | 14 ++++----------
> >  1 file changed, 4 insertions(+), 10 deletions(-)
> >
> > diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> > index 1e23faa364b1..f147e13a7017 100644
> > --- a/tools/perf/util/parse-events.c
> > +++ b/tools/perf/util/parse-events.c
> > @@ -2406,9 +2406,8 @@ foreach_evsel_in_last_glob(struct evlist *evlist,
> >  static int set_filter(struct evsel *evsel, const void *arg)
> >  {
> >       const char *str = arg;
> > -     bool found = false;
> >       int nr_addr_filters = 0;
> > -     struct perf_pmu *pmu = NULL;
> > +     struct perf_pmu *pmu;
> >
> >       if (evsel == NULL) {
> >               fprintf(stderr,
> > @@ -2426,16 +2425,11 @@ static int set_filter(struct evsel *evsel, const void *arg)
> >               return 0;
> >       }
> >
> > -     while ((pmu = perf_pmus__scan(pmu)) != NULL)
> > -             if (pmu->type == evsel->core.attr.type) {
> > -                     found = true;
> > -                     break;
> > -             }
> > -
> > -     if (found)
> > +     pmu = evsel__find_pmu(evsel);
> > +     if (pmu) {
> >               perf_pmu__scan_file(pmu, "nr_addr_filters",
> >                                   "%d", &nr_addr_filters);
> > -
> > +     }
> >       if (!nr_addr_filters)
> >               return perf_bpf_filter__parse(&evsel->bpf_filters, str);
> >
> > --
> > 2.47.1.613.gc27f4b7a9f-goog