linux-kernel - Re: [PATCH V1 22/23] perf tools: Allow system-wide events to keep their own CPUs

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Message-ID: <CAP-5=fVxPE7D=RBMnapByyzsiKAS_MxBqz5_=0NcOyha_5Huiw@mail.gmail.com>
Date:   Thu, 5 May 2022 18:00:12 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Alexey Bayduraev <alexey.v.bayduraev@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Leo Yan <leo.yan@...aro.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V1 22/23] perf tools: Allow system-wide events to keep
 their own CPUs

On Thu, May 5, 2022 at 9:58 AM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> Currently, user_requested_cpus supplants system-wide CPUs when the evlist
> has_user_cpus. Change that so that system-wide events retain their own
> CPUs and they are added to all_cpus.
>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>

Acked-by: Ian Rogers <irogers@...gle.com>

Note, we should really have a test on:
```
$ perf stat -A -e uncore_imc/cas_count_read/ -a -C 1,19 sleep 1

 Performance counter stats for 'system wide':

CPU1                   974.34 MiB  uncore_imc/cas_count_read/
CPU19                  262.50 MiB  uncore_imc/cas_count_read/

       1.003673356 seconds time elapsed
```
ie the user requested CPUs were respected for the uncore events even
though their CPU mask was {0,18}.

Thanks,
Ian

> ---
>  tools/lib/perf/evlist.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
> index 3bf77f9617b6..da30e88c76b9 100644
> --- a/tools/lib/perf/evlist.c
> +++ b/tools/lib/perf/evlist.c
> @@ -40,12 +40,11 @@ static void __perf_evlist__propagate_maps(struct perf_evlist *evlist,
>          * We already have cpus for evsel (via PMU sysfs) so
>          * keep it, if there's no target cpu list defined.
>          */
> -       if (!evsel->own_cpus || evlist->has_user_cpus) {
> -               perf_cpu_map__put(evsel->cpus);
> -               evsel->cpus = perf_cpu_map__get(evlist->user_requested_cpus);
> -       } else if (!evsel->system_wide &&
> -                  !evsel->requires_cpu &&
> -                  perf_cpu_map__empty(evlist->user_requested_cpus)) {
> +       if (!evsel->own_cpus ||
> +           (!evsel->system_wide && evlist->has_user_cpus) ||
> +           (!evsel->system_wide &&
> +            !evsel->requires_cpu &&
> +            perf_cpu_map__empty(evlist->user_requested_cpus))) {
>                 perf_cpu_map__put(evsel->cpus);
>                 evsel->cpus = perf_cpu_map__get(evlist->user_requested_cpus);
>         } else if (evsel->cpus != evsel->own_cpus) {
> --
> 2.25.1
>