Re: [PATCH 2/5] perf evlist: Add evlist__findnew_tracking_event() helper

[Yang Jihong]

Hello,

On 2023/7/11 21:13, Adrian Hunter wrote:
> On 4/07/23 10:42, Yang Jihong wrote:
> > Currently, intel-bts, intel-pt, and arm-spe may add a dummy event for
> > tracking to the evlist. We may need to search for the dummy event for
> > some settings. Therefore, add evlist__findnew_tracking_event() helper.
> >
> > Signed-off-by: Yang Jihong <yangjihong1@xxxxxxxxxx>
> > ---
> >   tools/perf/builtin-record.c | 11 +++--------
> >   tools/perf/util/evlist.c    | 17 +++++++++++++++++
> >   tools/perf/util/evlist.h    |  1 +
> >   3 files changed, 21 insertions(+), 8 deletions(-)
> >
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index aec18db7ff23..8872cd037f2c 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -1295,14 +1295,9 @@ static int record__open(struct record *rec)
> >   	 */
> >   	if (opts->target.initial_delay || target__has_cpu(&opts->target) ||
> >   	    perf_pmus__num_core_pmus() > 1) {
> > -		pos = evlist__get_tracking_event(evlist);
> > -		if (!evsel__is_dummy_event(pos)) {
> > -			/* Set up dummy event. */
> > -			if (evlist__add_dummy(evlist))
> > -				return -ENOMEM;
> > -			pos = evlist__last(evlist);
> > -			evlist__set_tracking_event(evlist, pos);
> > -		}
> > +		pos = evlist__findnew_tracking_event(evlist);
> > +		if (!pos)
> > +			return -ENOMEM;
> >   
> >   		/*
> >   		 * Enable the dummy event when the process is forked for
> > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> > index 7ef43f72098e..4621ddaeb8f3 100644
> > --- a/tools/perf/util/evlist.c
> > +++ b/tools/perf/util/evlist.c
> > @@ -1694,6 +1694,23 @@ void evlist__set_tracking_event(struct evlist *evlist, struct evsel *tracking_ev
> >   	tracking_evsel->tracking = true;
> >   }
> >   
> > +struct evsel *evlist__findnew_tracking_event(struct evlist *evlist)
> > +{
> > +	struct evsel *evsel;
> > +
> > +	evsel = evlist__get_tracking_event(evlist);
> > +	if (!evsel__is_dummy_event(evsel)) {
> > +		/* Set up dummy event. */
> > +		if (evlist__add_dummy(evlist))
>
> evlist__add_dummy() does not exclude_kernel so it
> will end up relying on evsel__fallback() to work in
> cases where the user does not have kernel access.
>
> evlist__add_aux_dummy() is probably better suited.
> Consequently perhaps pass system_wide as
> a parameter to evlist__findnew_tracking_event() and
> deal with that all inside evlist__findnew_tracking_event()
OK. These two points will be modified in the next version.

Thanks,
Yang