linux-kernel - Re: [PATCH 03/22] perf stat: Switch aggregation to use for

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Date:   Sat, 11 Dec 2021 20:24:54 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        John Garry <john.garry@...wei.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        "Paul A . Clarke" <pc@...ibm.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Riccardo Mancini <rickyman7@...il.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Vineet Singh <vineet.singh@...el.com>,
        James Clark <james.clark@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, eranian@...gle.com
Subject: Re: [PATCH 03/22] perf stat: Switch aggregation to use for_each loop

On Tue, Dec 07, 2021 at 06:45:48PM -0800, Ian Rogers wrote:
> Tidy up the use of cpu and index to hopefully make the code less error
> prone. Avoid unused warnings with (void) which will be removed in a
> later patch.
> 
> In aggr_update_shadow, the perf_cpu_map is switched from
> the evlist to the counter's cpu map, so the index is appropriate. This
> addresses a problem where uncore counts, with a cpumap like:
> $ cat /sys/devices/uncore_imc_0/cpumask
> 0,18
> Don't aggregate counts in CPUs based on the index of those values in the
> cpumap (0 and 1) but on the actual CPU (0 and 18). Thereby correcting
> metric calculations in per-socket mode for counters with without a full
> cpumask.
> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/stat-display.c | 48 +++++++++++++++++++---------------
>  1 file changed, 27 insertions(+), 21 deletions(-)
> 
> diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> index 588601000f3f..efab39a759ff 100644
> --- a/tools/perf/util/stat-display.c
> +++ b/tools/perf/util/stat-display.c
> @@ -330,8 +330,8 @@ static void print_metric_header(struct perf_stat_config *config,
>  static int first_shadow_cpu(struct perf_stat_config *config,
>  			    struct evsel *evsel, struct aggr_cpu_id id)
>  {
> -	struct evlist *evlist = evsel->evlist;
> -	int i;
> +	struct perf_cpu_map *cpus;
> +	int cpu, idx;
>  
>  	if (config->aggr_mode == AGGR_NONE)
>  		return id.core;
> @@ -339,14 +339,11 @@ static int first_shadow_cpu(struct perf_stat_config *config,
>  	if (!config->aggr_get_id)
>  		return 0;
>  
> -	for (i = 0; i < evsel__nr_cpus(evsel); i++) {
> -		int cpu2 = evsel__cpus(evsel)->map[i];
> -
> -		if (cpu_map__compare_aggr_cpu_id(
> -					config->aggr_get_id(config, evlist->core.cpus, cpu2),
> -					id)) {
> -			return cpu2;
> -		}
> +	cpus = evsel__cpus(evsel);
> +	perf_cpu_map__for_each_cpu(cpu, idx, cpus) {
> +		if (cpu_map__compare_aggr_cpu_id(config->aggr_get_id(config, cpus, idx),
> +						 id))
> +			return cpu;

so this looks strange, you pass idx instead of cpu2 to aggr_get_id,
which takes idx as 3rd argument, so it looks like it was broken now,
should this be a separate fix?

also the original code for some reason passed evlist->core.cpus
to aggr_get_id, which might differ rom evsel's cpus

same for aggr_update_shadow change

jirka