linux-kernel - Re: [PATCH] perf record: Fix wrong comm in system-wide mode with delay

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Message-ID: <YS0pcjdivueJcdwd@kernel.org>
Date:   Mon, 30 Aug 2021 15:54:42 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf record: Fix wrong comm in system-wide mode with
 delay

Em Mon, Aug 30, 2021 at 10:33:16AM -0700, Ian Rogers escreveu:
> On Fri, Aug 27, 2021 at 4:32 PM Namhyung Kim <namhyung@...nel.org> wrote:
> > Stephane found that the name of the forked process in a system-wide
> > mode is wrong when --delay option is used.  For example,
> >
> >   # perf record -a --delay=1000  noploop 3
> >
> > The noploop process will run a busy loop for 3 second.  And on an idle
> > machine it should show up at the top in the perf report.  It works
> > well without the --delay option.  But if I add the option, it showed
> > 'perf' not 'noploop'.
> >
> >   # perf report -s comm -q | head -3
> >       52.94%  perf
> >       16.65%  swapper
> >       12.04%  chrome
> >
> > It turned out that the dummy event didn't work at all and it missed
> > COMM and MMAP events for the noploop process (and others too).  We
> > should enable the dummy event immediately in system-wide mode, as the
> > enable-on-exec would work only for task events.
> >
> > With this change,
> >
> >   # perf report -s comm -q | head -3
> >       52.75%  noploop
> >       17.03%  swapper
> >       12.83%  chrome
> >
> > Cc: Adrian Hunter <adrian.hunter@...el.com>
> > Reported-by: Stephane Eranian <eranian@...gle.com>
> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> 
> Acked-by: Ian Rogers <irogers@...gle.com>

Thanks, applied.

- Arnaldo