Re: [PATCH 1/4] perf evsel: Add evsel__clone() function

[Namhyung Kim]

Hi Jiri,

On Thu, Sep 10, 2020 at 5:59 PM Jiri Olsa <jolsa@xxxxxxxxxx> 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@xxxxxxxxxx>
> > ---
> >  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