Re: [PATCH v2 1/4] perf pmu: Correct perf_pmu__auto_merge_stats affecting hybrid

[Liang, Kan]

On 2023-06-01 4:29 a.m., Ian Rogers wrote:
> Flip the return value correcting a bug.

The bug is that perf fails to create a normal core event on each hybrid
PMU even if the event is available on all hybrid PMUs.

Without the patch,

 # ./perf_old stat -e inst_retired.any -a sleep 1

 Performance counter stats for 'system wide':

        21,760,495      cpu_core/inst_retired.any/

       1.004010591 seconds time elapsed

With the patch,

 # ./perf stat -e inst_retired.any -a sleep 1

 Performance counter stats for 'system wide':

        19,874,833      cpu_core/inst_retired.any/
         3,102,256      cpu_atom/inst_retired.any/

       1.004081307 seconds time elapsed

I think we need to fold the above to the description.

Thanks,
Kan
> 
> Fixes: 6b9da2607030 ("perf pmu: Remove is_pmu_hybrid")
> Reported-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> ---
>  tools/perf/util/pmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index 0520aa9fe991..36e163f38368 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -1424,7 +1424,7 @@ bool perf_pmu__supports_legacy_cache(const struct perf_pmu *pmu)
>  
>  bool perf_pmu__auto_merge_stats(const struct perf_pmu *pmu)
>  {
> -	return pmu->is_core && perf_pmus__num_core_pmus() > 1;
> +	return pmu->is_core && perf_pmus__num_core_pmus() == 1;
>  }
>  
>  bool perf_pmu__have_event(const struct perf_pmu *pmu, const char *name)