linux-kernel - Re: [PATCH 02/19] perf tools: Use pmu info in evsel__is

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Message-ID: <CAM9d7ci9iz8ciQTw4YnabOgaY-izF+yGCeBawx-1fn2syVZ-Mw@mail.gmail.com>
Date:   Mon, 10 Oct 2022 22:10:48 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org,
        Kan Liang <kan.liang@...ux.intel.com>,
        Leo Yan <leo.yan@...aro.org>, Andi Kleen <ak@...ux.intel.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        James Clark <james.clark@....com>,
        Xing Zhengjun <zhengjun.xing@...ux.intel.com>
Subject: Re: [PATCH 02/19] perf tools: Use pmu info in evsel__is_hybrid()

Hi Ian,

On Mon, Oct 10, 2022 at 3:31 PM Ian Rogers <irogers@...gle.com> wrote:
>
> On Sun, Oct 9, 2022 at 10:36 PM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > If evsel has pmu, it can use pmu->is_hybrid directly.
> >
> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> > ---
> >  tools/perf/util/evsel.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > index 196f8e4859d7..a6ea91c72659 100644
> > --- a/tools/perf/util/evsel.c
> > +++ b/tools/perf/util/evsel.c
> > @@ -3132,6 +3132,9 @@ void evsel__zero_per_pkg(struct evsel *evsel)
> >
> >  bool evsel__is_hybrid(struct evsel *evsel)
> >  {
> > +       if (evsel->pmu)
> > +               return evsel->pmu->is_hybrid;
> > +
> >         return evsel->pmu_name && perf_pmu__is_hybrid(evsel->pmu_name);
>
> Wow, there's so much duplicated state. Why do evsels have a pmu_name
> and a pmu? Why not just pmu->name? I feel always having a pmu would be
> cleanest here.

Thanks a lot Ian for your detailed review!

The evsel->pmu was added recently for checking missing features.
And I just made it to have the pmu info when parsing events.

I guess it has pmu_name because it didn't want to add pmu.c dependency
to the python module.  But this change only adds pmu.h dependency.


> That said what does evsel__is_hybrid even mean? Does it
> mean this event is on a PMU normally called cpu and called cpu_core
> and cpu_atom on hybrid systems? And of course there are no comments to
> explain what this little mystery could be.

I believe so.


> Anyway, that's not a fault
> of this change, and probably later changes will go someway toward
> cleaning this up. It was a shame the code wasn't cleaner in the first
> place.
>
> Acked-by: Ian Rogers

Thanks,
Namhyung