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

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Date:   Fri, 28 Apr 2023 22:44:34 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>,
        Song Liu <songliubraving@...com>
Cc:     Dmitry Dolgov <9erthalion6@...il.com>,
        linux-perf-users@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        mingo@...hat.com, jolsa@...nel.org, namhyung@...nel.org,
        irogers@...gle.com
Subject: Re: [RFC PATCH] perf stat: Separate bperf from bpf_profiler

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?

- Arnaldo