linux-kernel - Re: [GIT PULL] perf tools changes for v5.19: 2nd batch

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Date:   Sun, 29 May 2022 23:32:00 +0200
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
CC:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Clark Williams <williams@...hat.com>,
        Kate Carcia <kcarcia@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org,
        Adrian Hunter <adrian.hunter@...el.com>,
        Carsten Haitzler <carsten.haitzler@....com>,
        Claire Jensen <cjense@...gle.com>,
        Dmitriy Vyukov <dvyukov@...gle.com>,
        Eelco Chaudron <echaudro@...hat.com>,
        Eric Lin <eric.lin@...ive.com>,
        Florian Fischer <florian.fischer@...q.space>,
        German Gomez <german.gomez@....com>,
        Ian Rogers <irogers@...gle.com>,
        James Clark <james.clark@....com>,
        Joe Mario <jmario@...hat.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Leo Yan <leo.yan@...aro.org>,
        Martin Liška <mliska@...e.cz>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Xing Zhengjun <zhengjun.xing@...ux.intel.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        anicolas@...stream.com
Subject: Re: [GIT PULL] perf tools changes for v5.19: 2nd batch



On May 29, 2022 7:28:26 PM GMT+02:00, Linus Torvalds <torvalds@...ux-foundation.org> wrote:
>On Sun, May 29, 2022 at 8:45 AM Arnaldo Carvalho de Melo
><acme@...nel.org> wrote:
>>
>> - Add BPF based off-CPU profiling.
>
>I suspect this could have come with a bit more explanation of what
>"off-CPU profiling" means.

Sorry about that, I was in a hurry, traveling to Paris for Kernel Recipes[1], afraid to miss the merge window.

>It seems to be "account time when process was scheduled away to
>caller", but I had to go look at the commits to figure that out.

Thanks for merging!

>Partly unrelated side note: I've occasionally looked for "useful perf
>recipes". Not from kernel developers, but from people who solved real
>performance problems using perf, giving useful examples.

Yeah, collecting such experiences somewhere and trying to reduce boilerplate to achieve the results sometimes ends up creating new tools or making the existing ones now actionable.

When people ask me about such recipes I usually point them to:

https://www.brendangregg.com/perf.html

Lots of features in perf came from trying to address comments, complaints from you, Ingo, Peter, Thomas, Milian Wolff, Brendan, Stephane and lots of others, thanks!

Back to this off-CPU thing, I'm talking with Namhyung on how to streamline it, this one and the growing number of BPF based perf tools,

- Arnaldo

[1] https://kernel-recipes.org/en/2022/