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

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Message-ID: <20200526115155.GE333164@krava>
Date:   Tue, 26 May 2020 13:51:55 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Jin Yao <yao.jin@...ux.intel.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

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


        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