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

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Date:   Wed, 27 May 2020 11:20:42 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v2 1/2] perf evlist: Ensure grouped events with same cpu
 map

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