[Intel-gfx] [PATCH 30/37] drm/i915: Exercise filling and removing random ranges from the live GTT

Chris Wilson chris at chris-wilson.co.uk
Fri Jan 13 09:08:40 UTC 2017

On Fri, Jan 13, 2017 at 10:59:52AM +0200, Joonas Lahtinen wrote:
> On ke, 2017-01-11 at 21:09 +0000, Chris Wilson wrote:
> > +		       struct i915_address_space *vm,
> > +		       u64 hole_start, u64 hole_end)
> > +{
> > +	I915_RND_STATE(prng);
> Just to remind that this prng should be seeded from the user seed to
> maintain repeatability. I kinda assume it's so.

I915_RND_STATE() does the initialisation from the user seed. But as we
were discussing on IRC, since the inner loop has variable length (due to
each being limited by the user timeout), we need to reseed at the
beginning of each loop. As the loops are fairly uniform, we want to
reseed using the prng(user_seed) to try and avoid falling into the trap
of pattern repetition.

Chris Wilson, Intel Open Source Technology Centre

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