linux-kernel - Re: [PATCH v15 10/10] perf test: Add direct off-cpu test

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Message-ID: <CAP-5=fXae_851WezB5rNkv6cp2DfAWobJ-cbehKy3eiFe8F9Ow@mail.gmail.com>
Date: Tue, 18 Feb 2025 11:32:33 -0800
From: Ian Rogers <irogers@...gle.com>
To: Howard Chu <howardchu95@...il.com>
Cc: acme@...nel.org, namhyung@...nel.org, jolsa@...nel.org, 
	adrian.hunter@...el.com, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Ingo Molnar <mingo@...hat.com>, 
	James Clark <james.clark@...aro.org>, Kan Liang <kan.liang@...ux.intel.com>, 
	Mark Rutland <mark.rutland@....com>, Peter Zijlstra <peterz@...radead.org>, 
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH v15 10/10] perf test: Add direct off-cpu test

On Thu, Feb 13, 2025 at 3:04 PM Howard Chu <howardchu95@...il.com> wrote:
>
> Hello,
>
> On Thu, Feb 13, 2025 at 3:00 PM Howard Chu <howardchu95@...il.com> wrote:
> >
> > Why is there a --off-cpu-thresh 2000?
> >
> > We collect an off-cpu period __ONLY ONCE__, either in direct sample form,
> > or in accumulated form (in BPF stack trace map).
> >
> > If I don't add --off-cpu-thresh 2000, the sample in the original test
> > goes into the ring buffer instead of the BPF stack trace map.
> >
> > Additionally, when using -e dummy, the ring buffer is not open, causing
> > us to lose a sample.
>
> Just noticed that this commit message is wrong, should be:
> """
> Add tests for direct off-cpu samples and --off-cpu-thresh option.
> """

Tested-by: Ian Rogers <irogers@...gle.com>
```
121: perf record offcpu profiling tests                              : Ok
```
I'd be tempted to keep the comments about why 2000 next to the actual
code rather than in the commit message. In the code the value is 12000
and not 2000 though?

Thanks,
Ian