linux-kernel - Re: [PATCH v1] perf stat display: Make %f precision consistent

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Message-ID: <CAP-5=fVf=Db9+9gxmfoRPDZvp_jz3bwG9FqLwAnKVHjaHbe4MQ@mail.gmail.com>
Date: Thu, 8 Jan 2026 11:25:17 -0800
From: Ian Rogers <irogers@...gle.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, James Clark <james.clark@...aro.org>, 
	Chun-Tse Shao <ctshao@...gle.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v1] perf stat display: Make %f precision consistent

On Tue, Dec 9, 2025 at 9:45 AM Ingo Molnar <mingo@...nel.org> wrote:
>
> * Ian Rogers <irogers@...gle.com> wrote:
>
> > Commit bc22de9bcdb2 ("perf stat: Display time in precision based on
> > std deviation") added multirun workload elapsed time. There was an
> > effort to make the precision in the output most useful for the user,
> > however, when gathering over runs it means the formatting varies. This
> > change just makes the output format fixed.
> >
> > Before:
> > ```
> > $ while :; do perf stat --null --repeat 3 sleep 0.1 2>&1 | grep elapsed; done
> >           0.101140 +- 0.000149 seconds time elapsed  ( +-  0.15% )
> >          0.1011396 +- 0.0000218 seconds time elapsed  ( +-  0.02% )
> >           0.101331 +- 0.000124 seconds time elapsed  ( +-  0.12% )
> > ^C
> > $ while :; do perf stat --null --repeat 3 sleep 1 2>&1 | grep elapsed; done
> >           1.001317 +- 0.000146 seconds time elapsed  ( +-  0.01% )
> >           1.001377 +- 0.000172 seconds time elapsed  ( +-  0.02% )
> >            1.00253 +- 0.00131 seconds time elapsed  ( +-  0.13% )
> > ```
> >
> > After:
> > ```
> > $ while :; do perf stat --null --repeat 3 sleep 0.1 2>&1 | grep elapsed; done
> >        0.101406408 +- 0.000064778 seconds time elapsed  ( +-  0.06% )
> >        0.101367315 +- 0.000027253 seconds time elapsed  ( +-  0.03% )
> >        0.101434164 +- 0.000084750 seconds time elapsed  ( +-  0.08% )
> > ^C
> > $ while :; do perf stat --null --repeat 3 sleep 1 2>&1 | grep elapsed; done
> >        1.001525467 +- 0.000051703 seconds time elapsed  ( +-  0.01% )
> >        1.001375093 +- 0.000116200 seconds time elapsed  ( +-  0.01% )
> >        1.001141025 +- 0.000046361 seconds time elapsed  ( +-  0.00% )
>
> Perfect, thank you!
>
> Tested-by: Ingo Molnar <mingo@...nel.org>

Ping.

Thanks,
Ian

>         Ingo
>