linux-kernel - Re: [PATCH RFC 02/21] libperf evsel: Add perf_evsel__enable

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Date:   Tue, 3 May 2022 09:45:33 -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 RFC 02/21] libperf evsel: Add perf_evsel__enable_thread()

On Fri, Apr 22, 2022 at 9:24 AM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> Add perf_evsel__enable_thread() as a counterpart to
> perf_evsel__enable_cpu(), to enable all events for a thread.
>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>  tools/lib/perf/evsel.c              | 10 ++++++++++
>  tools/lib/perf/include/perf/evsel.h |  1 +
>  2 files changed, 11 insertions(+)
>
> diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
> index 20ae9f5f8b30..2a1f07f877be 100644
> --- a/tools/lib/perf/evsel.c
> +++ b/tools/lib/perf/evsel.c
> @@ -360,6 +360,16 @@ int perf_evsel__enable_cpu(struct perf_evsel *evsel, int cpu_map_idx)
>         return perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_ENABLE, NULL, cpu_map_idx);
>  }
>
> +int perf_evsel__enable_thread(struct perf_evsel *evsel, int thread)
> +{
> +       int err = 0;
> +       int i;
> +
> +       for (i = 0; i < xyarray__max_x(evsel->fd) && !err; i++)
> +               err = perf_evsel__ioctl(evsel, PERF_EVENT_IOC_ENABLE, NULL, i, thread);

Looking at the argument names to perf_evsel__ioctl, i is the
cpu_map_idx. Would it be more intention revealing here to do:

perf_cpu_map__for_each_cpu(cpu, idx, evsel->cpus) {
   if (err = perf_evsel__ioctl(evsel, PERF_EVENT_IOC_ENABLE, NULL, idx, thread))
     break;
}

or perhaps:

for (idx = 0; idx < perf_cpu_map__nr(evsel->fd) && !err; idx++)

Thanks,
Ian

> +       return err;
> +}
> +
>  int perf_evsel__enable(struct perf_evsel *evsel)
>  {
>         int i;
> diff --git a/tools/lib/perf/include/perf/evsel.h b/tools/lib/perf/include/perf/evsel.h
> index 2a9516b42d15..699c0ed97d34 100644
> --- a/tools/lib/perf/include/perf/evsel.h
> +++ b/tools/lib/perf/include/perf/evsel.h
> @@ -36,6 +36,7 @@ LIBPERF_API int perf_evsel__read(struct perf_evsel *evsel, int cpu_map_idx, int
>                                  struct perf_counts_values *count);
>  LIBPERF_API int perf_evsel__enable(struct perf_evsel *evsel);
>  LIBPERF_API int perf_evsel__enable_cpu(struct perf_evsel *evsel, int cpu_map_idx);
> +LIBPERF_API int perf_evsel__enable_thread(struct perf_evsel *evsel, int thread);
>  LIBPERF_API int perf_evsel__disable(struct perf_evsel *evsel);
>  LIBPERF_API int perf_evsel__disable_cpu(struct perf_evsel *evsel, int cpu_map_idx);
>  LIBPERF_API struct perf_cpu_map *perf_evsel__cpus(struct perf_evsel *evsel);
> --
> 2.25.1
>