Re: [PATCH v2 1/2] perf evlist: Ensure grouped events with same cpu map

[Jin, Yao]

Hi Jiri,

On 5/26/2020 7:51 PM, Jiri Olsa wrote:
> On Mon, May 25, 2020 at 02:55:58PM +0800, Jin Yao wrote:
>
> SNIP
>
> > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> > index 2a9de6491700..1161cffc0688 100644
> > --- a/tools/perf/util/evlist.c
> > +++ b/tools/perf/util/evlist.c
> > @@ -1704,3 +1704,52 @@ struct evsel *perf_evlist__reset_weak_group(struct evlist *evsel_list,
> >   	}
> >   	return leader;
> >   }
> > +
> > +static bool cpus_map_matched(struct evsel *prev, struct evsel *evsel)
> > +{
> > +	if (evsel->core.cpus->nr != prev->core.cpus->nr)
> > +		return false;
> > +
> > +	for (int i = 0; i < evsel->core.cpus->nr; i++) {
> > +		if (evsel->core.cpus->map[i] != prev->core.cpus->map[i])
> > +			return false;
> > +	}
> > +
> > +	return true;
> > +}
> > +
> > +bool evlist__cpus_map_matched(struct evlist *evlist)
> > +{
> > +	struct evsel *prev = evlist__first(evlist), *evsel = prev;
> > +	int nr_members = prev->core.nr_members;
> > +
> > +	evlist__for_each_entry_continue(evlist, evsel) {
> > +		if (nr_members <= 1) {
> > +			prev = evsel;
> > +			nr_members = evsel->core.nr_members;
> > +			continue;
> > +		}
> > +
> > +		nr_members--;
> > +
> > +		if (!cpus_map_matched(prev, evsel))
> > +			return false;
> > +
> > +		prev = evsel;
> > +	}
> > +
> > +	return true;
> > +}
> > +
> > +void evlist__force_disable_group(struct evlist *evlist)
> > +{
> > +	struct evsel *evsel;
> > +
> > +	pr_warning("WARNING: event cpu maps are not fully matched, "
> > +		   "stop event grouping\n");
> > +
> > +	evlist__for_each_entry(evlist, evsel) {
> > +		evsel->leader = evsel;
> > +		evsel->core.nr_members = 0;
> > +	}
> > +}
>
> I think this is too much, we need to disable only groups with not
> matching cpus, not all of them, how about something like this

Yes, that's too much.

>          struct evsel *pos;
>
>          evlist__for_each_entry(evlist, evsel) {
>                  if (evsel->leader == evsel)
>                          continue;
>                  if (!cpus_map_matched(evsel->leader, evsel))
>                          continue;
>                          
>                  pr_warn("Disabling group...
>
>                  for_each_group_member(pos, evsel->leader) {
>                          pos->leader = pos;
>                          evsel->core.nr_members = 0;
>                  }
>          }
>
> jirka

Hmm, change "!cpus_map_matched()" to "cpus_map_matched()"? and use for_each_group_evsel() to replace 
for_each_group_member()?

How about something like following?

void evlist__check_cpu_maps(struct evlist *evlist)
{
	struct evsel *evsel, *pos;

	evlist__for_each_entry(evlist, evsel) {
		if (evsel->leader == evsel)
			continue;

		if (cpu_maps_matched(evsel->leader, evsel))
			continue;

		pr_warning("WARNING: event cpu maps are not fully matched, "
			   "disable group\n");

		for_each_group_evsel(pos, evsel->leader) {
			pos->leader = pos;
			pos->core.nr_members = 0;
		}

		/*
		 * For core & uncore mixed event group, for example,
		 * '{cycles,unc_cbo_cache_lookup.any_i}',
		 * In evlist:
		 * cycles,
		 * unc_cbo_cache_lookup.any_i,
		 * unc_cbo_cache_lookup.any_i,
		 * unc_cbo_cache_lookup.any_i,
		 * unc_cbo_cache_lookup.any_i,
		 *
		 * cycles is leader and all unc_cbo_cache_lookup.any_i
		 * point to this leader. But for_each_group_evsel can't
		 * iterate all members from cycles. It only iterates
		 * cycles and one unc_cbo_cache_lookup.any_i. So we
		 * set extra evsel here.
		 */
		evsel->leader = evsel;
		evsel->core.nr_members = 0;
	}
}

Thanks
Jin Yao