Subject: Re: [PATCH v3 03/48] perf stat: Correct aggregation CPU map

From: Jiri Olsa <[email-masked]>
Date: Tue, 4 Jan 2022 15:19:35 +0100

On Wed, Dec 29, 2021 at 11:19:45PM -0800, Ian Rogers wrote:
> Switch the perf_cpu_map in aggr_update_shadow 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 without a full
> cpumask.
> 
> On a SkylakeX with a tweaked DRAM_BW_Use metric, to remove unnecessary
> scaling, this gives:
> 
> Before:
> $ /perf stat --per-socket -M DRAM_BW_Use -I 1000
>      1.001102293 S0        1              27.01 MiB  uncore_imc/cas_count_write/ #   103.00 DRAM_BW_Use
>      1.001102293 S0        1              30.22 MiB  uncore_imc/cas_count_read/
>      1.001102293 S0        1      1,001,102,293 ns   duration_time
>      1.001102293 S1        1              20.10 MiB  uncore_imc/cas_count_write/ #     0.00 DRAM_BW_Use
>      1.001102293 S1        1              32.74 MiB  uncore_imc/cas_count_read/
>      1.001102293 S1        0      <not counted> ns   duration_time
>      2.003517973 S0        1              83.04 MiB  uncore_imc/cas_count_write/ #   920.00 DRAM_BW_Use
>      2.003517973 S0        1             145.95 MiB  uncore_imc/cas_count_read/
>      2.003517973 S0        1      1,002,415,680 ns   duration_time
>      2.003517973 S1        1             302.45 MiB  uncore_imc/cas_count_write/ #     0.00 DRAM_BW_Use
>      2.003517973 S1        1             290.99 MiB  uncore_imc/cas_count_read/
>      2.003517973 S1        0      <not counted> ns   duration_time
> 
> After:
> $ perf stat --per-socket -M DRAM_BW_Use -I 1000
>      1.001080840 S0        1              24.96 MiB  uncore_imc/cas_count_write/ #    54.00 DRAM_BW_Use
>      1.001080840 S0        1              33.64 MiB  uncore_imc/cas_count_read/
>      1.001080840 S0        1      1,001,080,840 ns   duration_time
>      1.001080840 S1        1              42.43 MiB  uncore_imc/cas_count_write/ #    84.00 DRAM_BW_Use
>      1.001080840 S1        1              47.05 MiB  uncore_imc/cas_count_read/
>      1.001080840 S1        0      <not counted> ns   duration_time
> 
> Signed-off-by: Ian Rogers <[email-masked]>
> ---
>  tools/perf/util/stat-display.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> index 588601000f3f..b0fa81ffce61 100644
> --- a/tools/perf/util/stat-display.c
> +++ b/tools/perf/util/stat-display.c
> @@ -526,7 +526,7 @@ static void aggr_update_shadow(struct perf_stat_config *config,
>  		evlist__for_each_entry(evlist, counter) {
>  			val = 0;
>  			for (cpu = 0; cpu < evsel__nr_cpus(counter); cpu++) {
> -				s2 = config->aggr_get_id(config, evlist->core.cpus, cpu);
> +				s2 = config->aggr_get_id(config, evsel__cpus(counter), cpu);
>  				if (!cpu_map__compare_aggr_cpu_id(s2, id))
>  					continue;
>  				val += perf_counts(counter->counts, cpu, 0)->val;

makes sense, there's another instance of this in first_shadow_cpu

thanks,
jirka

> -- 
> 2.34.1.448.ga2b2bfdf31-goog
> 

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