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From:   Ian Rogers <irogers@google.com>
Date:   Sat, 7 Oct 2023 22:49:25 -0700
Message-ID: <CAP-5=fV3NO-3Q=7YQ0S6RNJUX1dWfszX-paFSPwniNhSokYRew@mail.gmail.com>
Subject: Re: [PATCH v1 6/7] perf pmu-events: Remember the events and metrics table
To:     Yang Jihong <yangjihong1@huawei.com>
Cc:     Suzuki K Poulose <suzuki.poulose@arm.com>,
        Mike Leach <mike.leach@linaro.org>,
        James Clark <james.clark@arm.com>,
        Leo Yan <leo.yan@linaro.org>,
        John Garry <john.g.garry@oracle.com>,
        Will Deacon <will@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Thomas Richter <tmricht@linux.ibm.com>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        Jing Zhang <renyu.zj@linux.alibaba.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
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On Sat, Oct 7, 2023 at 8:39=E2=80=AFPM Yang Jihong <yangjihong1@huawei.com>=
 wrote:
>
> Hello,
>
> On 2023/10/7 10:13, Ian Rogers wrote:
> > strcmp_cpuid_str performs regular expression comparisons. Avoid
> > repeated computation of the table by remembering the table in a
> > static.
> >
> > Signed-off-by: Ian Rogers <irogers@google.com>
> > ---
> >   tools/perf/pmu-events/jevents.py | 48 +++++++++++++++++++------------=
-
> >   1 file changed, 28 insertions(+), 20 deletions(-)
> >
> > diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/j=
events.py
> > index fd009752b427..8d8d5088c53c 100755
> > --- a/tools/perf/pmu-events/jevents.py
> > +++ b/tools/perf/pmu-events/jevents.py
> > @@ -978,28 +978,32 @@ int pmu_metrics_table__for_each_metric(const stru=
ct pmu_metrics_table *table,
> >
> >   const struct pmu_events_table *perf_pmu__find_events_table(struct per=
f_pmu *pmu)
> >   {
> > -        const struct pmu_events_table *table =3D NULL;
> > -        char *cpuid =3D perf_pmu__getcpuid(pmu);
> > +        static const struct pmu_events_table *table;
> >           size_t i;
> >
> > -        /* on some platforms which uses cpus map, cpuid can be NULL fo=
r
> > -         * PMUs other than CORE PMUs.
> > -         */
> > -        if (!cpuid)
> > -                return NULL;
> > -
> > -        i =3D 0;
> > -        for (;;) {
> > -                const struct pmu_events_map *map =3D &pmu_events_map[i=
++];
> > -                if (!map->arch)
> > -                        break;
> > -
> > -                if (!strcmp_cpuid_str(map->cpuid, cpuid)) {
> > -                        table =3D &map->event_table;
> > -                        break;
> > +        if (!table) {
> If there is no matched table in pmu_events_map,
> perf_pmu__find_events_table() will enter this branch for repeated search
> each time.
> Or do we need to use another variable to indicate whether the search has
> been performed?

Agreed, the behavior will match the existing behavior. Longer term I
want to remove this code. Do you have a scenario we should optimize
for here?

Thanks,
Ian

> Thanks,
> Yang