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From:   Namhyung Kim <namhyung@kernel.org>
Date:   Thu, 10 Sep 2020 22:18:25 +0900
Message-ID: <CAM9d7chYfxQWNkDVXk2vLPgn4EhkH3WcAve+zzVGc7Jshri5VA@mail.gmail.com>
Subject: Re: [PATCH 1/4] perf evsel: Add evsel__clone() function
To:     Jiri Olsa <jolsa@redhat.com>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Stephane Eranian <eranian@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Andi Kleen <andi@firstfloor.org>,
        Ian Rogers <irogers@google.com>
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Hi Jiri,

On Thu, Sep 10, 2020 at 5:59 PM Jiri Olsa <jolsa@redhat.com> wrote:
>
> On Tue, Sep 08, 2020 at 01:42:25PM +0900, Namhyung Kim wrote:
> > The evsel__clone() is to create an exactly same evsel from same
> > attributes.  Note that metric events will be handled by later patch.
> >
> > It will be used by perf stat to generate separate events for each
> > cgroup.
> >
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> >  tools/perf/util/evsel.c | 57 +++++++++++++++++++++++++++++++++++++++++
> >  tools/perf/util/evsel.h |  1 +
> >  2 files changed, 58 insertions(+)
> >
> > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > index fd865002cbbd..4f50f9499973 100644
> > --- a/tools/perf/util/evsel.c
> > +++ b/tools/perf/util/evsel.c
> > @@ -331,6 +331,63 @@ struct evsel *evsel__new_cycles(bool precise)
> >       goto out;
> >  }
> >
> > +/**
> > + * evsel__clone - create a new evsel copied from @orig
> > + * @orig: original evsel
> > + *
> > + * The assumption is that @orig is not configured nor opened yet.
> > + * So we only care about the attributes that can be set while it's parsed.
> > + */
> > +struct evsel *evsel__clone(struct evsel *orig)
> > +{
> > +     struct evsel *evsel;
> > +     struct evsel_config_term *pos, *tmp;
> > +
> > +     BUG_ON(orig->core.fd);
> > +
> > +     evsel = evsel__new(&orig->core.attr);
> > +     if (evsel == NULL)
> > +             return NULL;
> > +
> > +     *evsel = *orig;
>
> this seems wild ;-) I saw that assumption above,
> but I wonder we could add some check or zero/init
> the rest of the fields fields

Alternatively, we could only copy relevant fields explicitly.
Other fields will remain zero by evsel__new() above.
But it might be easy to be missed by future changes..

Thanks
Namhyung