linux-kernel - Re: [PATCH v2 2/2] perf record: Add --synth option

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Date:   Tue, 10 Aug 2021 21:33:59 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>,
        Stephane Eranian <eranian@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Jin Yao <yao.jin@...ux.intel.com>
Subject: Re: [PATCH v2 2/2] perf record: Add --synth option

Hi Jiri,

On Mon, Jul 26, 2021 at 6:15 AM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Fri, Jul 23, 2021 at 09:01:29PM -0700, Namhyung Kim wrote:
> > Add an option to control synthesize behavior.
> >
> >     --synth <no|all|task|mmap|cgroup>
> >                       Fine-tune event synthesis: default=all
> >
> > This can be useful when we know it doesn't need some synthesis like
> > in a specific usecase and/or when using pipe:
> >
> >   $ perf record -a --all-cgroups --synth cgroup -o- sleep 1 | \
> >   > perf report -i- -s cgroup
> >
> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> > ---
> >  tools/perf/Documentation/perf-record.txt |  9 +++++
> >  tools/perf/builtin-record.c              | 48 +++++++++++++++++++-----
> >  tools/perf/util/record.h                 |  1 +
> >  tools/perf/util/synthetic-events.c       | 28 ++++++++++++++
> >  tools/perf/util/synthetic-events.h       | 12 ++++++
> >  5 files changed, 89 insertions(+), 9 deletions(-)
> >
> > diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> > index d71bac847936..03a41bec0583 100644
> > --- a/tools/perf/Documentation/perf-record.txt
> > +++ b/tools/perf/Documentation/perf-record.txt
> > @@ -596,6 +596,15 @@ options.
> >  'perf record --dry-run -e' can act as a BPF script compiler if llvm.dump-obj
> >  in config file is set to true.
> >
> > +--synth=TYPE::
> > +Collect and synthesize given type of events (comma separated).
> > +Available types are:
> > +  'task'    - synthesize FORK and COMM events for each task
> > +  'mmap'    - synthesize MMAP events for each process (implies 'task')
> > +  'cgroup'  - synthesize CGROUP events for each cgroup
> > +  'all'     - synthesize all events (default)
> > +  'no'      - do not synthesize any of the above events
>
> this only affects events we take from proc right?

Right.

>
> should we perhaps mention it, because you'll get mmap
> events from kernel even if you specify --synth=task

Good point, will update.

Thanks,
Namhyung