[PATCH] drm/selftests/mm: reduce per-function stack usage

[Chris Wilson]

Quoting Arnd Bergmann (2020-05-29 21:43:47)
> On Fri, May 29, 2020 at 10:26 PM Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > Quoting Arnd Bergmann (2020-05-29 21:15:26)
> 
> > >
> > > diff --git a/drivers/gpu/drm/selftests/test-drm_mm.c b/drivers/gpu/drm/selftests/test-drm_mm.c
> > > index 9aabe82dcd3a..30108c330db8 100644
> > > --- a/drivers/gpu/drm/selftests/test-drm_mm.c
> > > +++ b/drivers/gpu/drm/selftests/test-drm_mm.c
> > > @@ -323,9 +323,8 @@ static bool expect_reserve_fail(struct drm_mm *mm, struct drm_mm_node *node)
> > >         return false;
> > >  }
> > >
> > > -static bool check_reserve_boundaries(struct drm_mm *mm,
> > > -                                    unsigned int count,
> > > -                                    u64 size)
> > > +static noinline_for_stack bool
> > > +check_reserve_boundaries(struct drm_mm *mm, unsigned int count, u64 size)
> > >  {
> > >         const struct boundary {
> >
> > It's this const [] right? Hmm, if we felt adventurous that could be a
> > small set of multiplication factors (0, -1, 1, count, count+1, ...) and
> > made static.
> 
> That was my first thought, but I couldn't figure out whether 'count'
> could be replaced by any compile-time constant.

I just realised I sent a sketch of a patch to the wrong place. If we
replace struct boundary with { int start; int size; const char *name; }
that should reduce it from 408 to 272. (Where start, size are the
multiples.)

Probably not worth the hassle, the saving is too small overall leaving
it uncomfortably close to a future warning.

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris