linux-kernel - Re: [RFC PATCH] perf stat: Separate bperf from bpf

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Date:   Fri, 5 May 2023 17:32:15 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Dmitry Dolgov <9erthalion6@...il.com>, Song Liu <song@...nel.org>
Cc:     Namhyung Kim <namhyung@...nel.org>,
        Song Liu <songliubraving@...com>,
        linux-perf-users@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        mingo@...hat.com, jolsa@...nel.org, irogers@...gle.com
Subject: Re: [RFC PATCH] perf stat: Separate bperf from bpf_profiler

Em Thu, May 04, 2023 at 07:01:04PM -0700, Song Liu escreveu:
> On Fri, Apr 28, 2023 at 6:44 PM Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> > Em Fri, Apr 21, 2023 at 10:56:10PM +0200, Dmitry Dolgov escreveu:
> > > > On Wed, Apr 12, 2023 at 08:23:16PM +0200, Dmitrii Dolgov wrote:
> > > > It seems that perf stat -b <prog id> doesn't produce any results:

> > > >     $ perf stat -e cycles -b 4 -I 10000 -vvv
> > > >     Control descriptor is not initialized
> > > >     cycles: 0 0 0
> > > >                 time        counts unit      events
> > > >     10.007641640    <not supported>      cycles

> > > > Looks like this happens because fentry/fexit progs are getting loaded, but the
> > > > corresponding perf event is not enabled and not added into the events bpf map.
> > > > I think there is some mixing up between two type of bpf support, one for bperf
> > > > and one for bpf_profiler. Both are identified via evsel__is_bpf, based on which
> > > > perf events are enabled, but for the latter (bpf_profiler) a perf event is
> > > > required. Using evsel__is_bperf to check only bperf produces expected results:

> > > Any thoughts on this? I would appreciate clarifications if I'm missing
> > > something.

> > Namhyung, Song, can you please take a look at this?

> Sorry for the late response. The fix looks good to me and worked well
> in my test.

> Reviewed-and-tested-by: Song Liu <song@...nel.org>

> I guess we also need:

> Fixes: 112cb56164bc2 ("perf stat: Introduce config stat.bpf-counter-events")

Thanks a lot, applied, and this is relevant in the current situation,
where we're trying to have Linux v6.4 perf tools building BPF skels by
default.

- Arnaldo