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From: Namhyung Kim <namhyung@kernel.org>
Date: Fri, 23 Feb 2024 18:27:24 -0800
Message-ID: <CAM9d7cg1RDHhaNr94+Gbk+UqZ18gidwDMJnhH2ad1E0Tw5X1xw@mail.gmail.com>
Subject: Re: [PATCH 2/2] perf test: Test FASYNC with watermark wakeups.
To: robert@ocallahan.org
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>, Kyle Huey <me@kylehuey.com>, Ian Rogers <irogers@google.com>, 
	Kyle Huey <khuey@kylehuey.com>, Peter Zijlstra <peterz@infradead.org>, 
	Ingo Molnar <mingo@redhat.com>, Mark Rutland <mark.rutland@arm.com>, 
	Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa <jolsa@kernel.org>, 
	Adrian Hunter <adrian.hunter@intel.com>, linux-perf-users@vger.kernel.org, 
	linux-kernel@vger.kernel.org
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Hello,

On Fri, Feb 23, 2024 at 1:44=E2=80=AFPM Robert O'Callahan <robert@ocallahan=
org> wrote:
>
> (I work with Kyle.)
>
> IMHO this is more of a bug fix than a feature. `man perf_event_open`
> expects this to work already: "watermark: If set, have an overflow
> notification happen when we cross the wakeup_watermark boundary" and
> later "Alternatively, the overflow events can be captured via a signal
> handler, by enabling I/O signaling".
>
> Bug fixes need regression tests. Such tests should fail on any kernel
> where the bug is present. It seems strange to expect each such test to
> detect whether the bug "should be fixed" in the kernel it's running on
> and skip when that's not the case. I haven't seen any other project
> try to do this. Instead (as in kernel selftests) the tests, the code
> under test, and any metadata about which tests are expected to pass
> are all in the repository together and updated together.
>
> It makes sense that tests for the code in tools/perf should not fail
> on older kernels, given that the code in tools/perf is expected to
> work on older kernels. But tests for bug fixes in the kernel itself
> should be expected to fail on older kernels and therefore should live
> somewhere else, IMHO.

I think it makes sense to put the test in the selftests and to be
deployed with the kernel.  AFAICS it doesn't have anything
specific to the perf tools and tests the general kernel behavior.

Thanks,
Namhyung