linux-kernel - Re: [RFC PATCH 1/1] drm/format-helper: Add KUnit tests for drm_fb_xrgb8888_to

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Date:   Thu, 2 Jun 2022 09:53:10 -0700
From:   Daniel Latypov <dlatypov@...gle.com>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     José Expósito <jose.exposito89@...il.com>,
        tzimmermann@...e.de, maarten.lankhorst@...ux.intel.com,
        mripard@...nel.org, airlied@...ux.ie, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kunit-dev@...glegroups.com
Subject: Re: [RFC PATCH 1/1] drm/format-helper: Add KUnit tests for drm_fb_xrgb8888_to_rgb332()

On Thu, Jun 2, 2022 at 9:27 AM Javier Martinez Canillas
<javierm@...hat.com> wrote:
> > +CFLAGS_drm_format_helper_test.o += $(DISABLE_STRUCTLEAK_PLUGIN)
> >
>
> A comment on why this is needed would useful.

Ah, I think that should not be necessary anymore.
We added this to some tests to mitigate against compilers that didn't
optimize away stack-local structs used internally in KUNIT_EXPECT*.
Functions with ~30 or so EXPECTs could get flagged for excessively
large stack frames.

But in 5.18, I had some patches to reduce the naive stack usage from
[48..88] => [8..32] bytes per EXPECT.
I also have some RFC patches out to get it down to [0, 24] bytes.

So going forward, this should only be necessary if you have something
like 100s of EXPECTs in a single function (in which case you should
also consider splitting that function up).

Daniel