Re: [PATCH V2 21/23] libperf evsel: Add comments for booleans

Ian Rogers
2022-05-06T20:52:03Z

On Fri, May 6, 2022 at 5:26 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>
> Add comments for 'system_wide' and 'requires_cpu' booleans
>
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
> tools/lib/perf/include/internal/evsel.h | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/tools/lib/perf/include/internal/evsel.h b/tools/lib/perf/include/internal/evsel.h
> index 77fbb8b97e5c..cc8f1ba790bd 100644
> --- a/tools/lib/perf/include/internal/evsel.h
> +++ b/tools/lib/perf/include/internal/evsel.h
> @@ -49,7 +49,16 @@ struct perf_evsel {
>
> /* parse modifier helper */
> int nr_members;
> + /*
> + * system_wide is for events that need to be on every CPU, irrespective
> + * of user requested CPUs or threads. Map propagation will not override
> + * this events own_cpus, which will contribute to evlist all_cpus.

So this muddies my understanding of cpus and own_cpus (sigh, again
undocumented). I believe cpus to be the set of CPUs (or any CPU, aka
dummy) that perf_event_open happens on. all_cpus in evlist is the
union of all the evsels cpus (ie not related to own_cpus as described
here). Own_cpus I believe to be what's computed at parse-event time
from sysfs. Is this a typo in the comment or quite likely my error?

Thanks,
Ian

> + */
> bool system_wide;
> + /*
> + * Some events, for example uncore events, require a CPU.
> + * i.e. it cannot be the 'any CPU' value of -1.
> + */
> bool requires_cpu;
> int idx;
> };
> --
> 2.25.1
>