linux-kernel - Re: [PATCH v1] perf stat: Avoid merging/aggregating metric counts twice

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Message-ID: <Y+VlyR9IF8Ky460u@kernel.org>
Date:   Thu, 9 Feb 2023 18:29:45 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Ian Rogers <irogers@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        James Clark <james.clark@....com>,
        Eduard Zingerman <eddyz87@...il.com>,
        Florian Fischer <florian.fischer@...q.space>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Stephane Eranian <eranian@...gle.com>,
        Perry Taylor <perry.taylor@...el.com>
Subject: Re: [PATCH v1] perf stat: Avoid merging/aggregating metric counts
 twice

Em Thu, Feb 09, 2023 at 11:06:22AM -0800, Namhyung Kim escreveu:
> On Wed, Feb 8, 2023 at 10:45 PM Ian Rogers <irogers@...gle.com> wrote:

> > The added perf_stat_merge_counters combines uncore counters. When
> > metrics are enabled, the counts are merged into a metric_leader
> > via the stat-shadow saved_value logic. As the leader now is
> > passed an aggregated count, it leads to all counters being added
> > together twice and counts appearing approximately doubled in
> > metrics.

> > This change disables the saved_value merging of counts for evsels
> > that are merged. It is recommended that later changes remove the
> > saved_value entirely as the two layers of aggregation in the code
> > is confusing.
 
> +1

'perf stat' code needs help, that I'm sure, its great that you guys are
looking/working at/on it, please continue.
 
> >
> > Fixes: 942c5593393d ("perf stat: Add perf_stat_merge_counters()")
> > Reported-by: Perry Taylor <perry.taylor@...el.com>
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> 
> Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks, applied.

- Arnaldo