linux-kernel - Re: [PATCH V2] perf stat: Fix the hard-coded metrics calculation on the hybrid

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Date: Fri, 7 Jun 2024 11:27:10 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: kan.liang@...ux.intel.com
Cc: acme@...nel.org, irogers@...gle.com, jolsa@...nel.org,
	adrian.hunter@...el.com, linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Khalil, Amiri" <amiri.khalil@...el.com>, stable@...r.kernel.org
Subject: Re: [PATCH V2] perf stat: Fix the hard-coded metrics calculation on
 the hybrid

On Thu, Jun 06, 2024 at 11:03:16AM -0700, kan.liang@...ux.intel.com wrote:
> From: Kan Liang <kan.liang@...ux.intel.com>
> 
> The hard-coded metrics is wrongly calculated on the hybrid machine.
> 
> $ perf stat -e cycles,instructions -a sleep 1
> 
>  Performance counter stats for 'system wide':
> 
>         18,205,487      cpu_atom/cycles/
>          9,733,603      cpu_core/cycles/
>          9,423,111      cpu_atom/instructions/     #  0.52  insn per cycle
>          4,268,965      cpu_core/instructions/     #  0.23  insn per cycle
> 
> The insn per cycle for cpu_core should be 4,268,965 / 9,733,603 = 0.44.
> 
> When finding the metric events, the find_stat() doesn't take the PMU
> type into account. The cpu_atom/cycles/ is wrongly used to calculate
> the IPC of the cpu_core.
> 
> In the hard-coded metrics, the events from a different PMU are only
> SW_CPU_CLOCK and SW_TASK_CLOCK. They both have the stat type,
> STAT_NSECS. Except the SW CLOCK events, check the PMU type as well.
> 
> Fixes: 0a57b910807a ("perf stat: Use counts rather than saved_value")
> Reported-by: "Khalil, Amiri" <amiri.khalil@...el.com>
> Reviewed-by: Ian Rogers <irogers@...gle.com>
> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
> Cc: stable@...r.kernel.org

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung


> ---
> 
> Changes since V1:
> - Don't check the PMU of the SW CLOCK events 
> 
>  tools/perf/util/stat-shadow.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
> index 3466aa952442..6bb975e46de3 100644
> --- a/tools/perf/util/stat-shadow.c
> +++ b/tools/perf/util/stat-shadow.c
> @@ -176,6 +176,13 @@ static double find_stat(const struct evsel *evsel, int aggr_idx, enum stat_type
>  		if (type != evsel__stat_type(cur))
>  			continue;
>  
> +		/*
> +		 * Except the SW CLOCK events,
> +		 * ignore if not the PMU we're looking for.
> +		 */
> +		if ((type != STAT_NSECS) && (evsel->pmu != cur->pmu))
> +			continue;
> +
>  		aggr = &cur->stats->aggr[aggr_idx];
>  		if (type == STAT_NSECS)
>  			return aggr->counts.val;
> -- 
> 2.35.1
>