linux-kernel - Re: [PATCH 1/2] kunit: Warn if tests are slow

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Message-ID: <CA+GJov6sQMmEiTQ7cupyC2cx-aWvV7M6ki4W8naEHyA8tbSbdg@mail.gmail.com>
Date:   Tue, 19 Sep 2023 15:48:55 -0400
From:   Rae Moar <rmoar@...gle.com>
To:     Maxime Ripard <mripard@...nel.org>
Cc:     Brendan Higgins <brendan.higgins@...ux.dev>,
        David Gow <davidgow@...gle.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Maíra Canal <mairacanal@...eup.net>,
        linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 1/2] kunit: Warn if tests are slow

On Mon, Sep 11, 2023 at 5:51 AM Maxime Ripard <mripard@...nel.org> wrote:
>
> Kunit recently gained support to setup attributes, the first one being
> the speed of a given test, then allowing to filter out slow tests.
>
> A slow test is defined in the documentation as taking more than one
> second. There's an another speed attribute called "super slow" but whose
> definition is less clear.
>
> Add support to the test runner to check the test execution time, and
> report tests that should be marked as slow but aren't.
>
> Signed-off-by: Maxime Ripard <mripard@...nel.org>

Hi!

I like this idea especially if it was helpful in identifying slow
tests already! I have a few thoughts on this. I share Jani's concern
for warning all tests on slow machines. I can think of a few options.

First, we could increase the threshold to about 2s even though that
would eliminate warnings on potentially slow tests. However, this
would point out the slowest tests.

Second, we could change this to warn users only when they choose by
making this a configurable option or making this a script to output a
list of all unmarked slow tests.

Third, we could leave this as is. As the KUnit warnings do not show up
in the kunit.py output and do not cause the test to fail in any way
they are relatively harmless if they are unwanted by the user.

Not quite sure which I prefer? The second option might be the cleanest
for the user and the time threshold could even be customizable. Let me
know what you think.

> ---
>  lib/kunit/test.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/lib/kunit/test.c b/lib/kunit/test.c
> index 49698a168437..a3b924501f3d 100644
> --- a/lib/kunit/test.c
> +++ b/lib/kunit/test.c
> @@ -379,6 +379,9 @@ static void kunit_run_case_internal(struct kunit *test,
>                                     struct kunit_suite *suite,
>                                     struct kunit_case *test_case)
>  {
> +       struct timespec64 start, end;
> +       struct timespec64 duration;
> +
>         if (suite->init) {
>                 int ret;
>
> @@ -390,7 +393,20 @@ static void kunit_run_case_internal(struct kunit *test,
>                 }
>         }
>
> +       ktime_get_ts64(&start);
> +
>         test_case->run_case(test);
> +
> +       ktime_get_ts64(&end);
> +
> +       duration = timespec64_sub(end, start);
> +
> +       if (duration.tv_sec >= 1 &&
> +           (test_case->attr.speed == KUNIT_SPEED_UNSET ||
> +            test_case->attr.speed >= KUNIT_SPEED_NORMAL))
> +               kunit_warn(test,
> +                          "Test should be marked slow (runtime: %lld.%09lds)",
> +                          duration.tv_sec, duration.tv_nsec);

I would consider moving this if statement into a separate function.

>  }
>
>  static void kunit_case_internal_cleanup(struct kunit *test)
>
> --
> 2.41.0
>
> --
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