[PATCH 2/2] drm/amdgpu: prevent command submission failures under memory pressure

[Marek Olšák]

On Fri, Sep 2, 2016 at 9:38 AM, Christian König <deathsimple at vodafone.de> wrote:
> Am 01.09.2016 um 16:33 schrieb Deucher, Alexander:
>
>> return r; > + > + return -ENOMEM; > +}
>
> Unreachable code. Other than that looks good.
>
>
> Ups, indeed just a merge error.
>
> With that fixed: Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
>
> Thanks for the review, I've just pushed the resulting patches to
> amd-staging-4.6.
>
> Marek you might want to try and raise the limits now how much VRAM can be
> used by a single command submission. If I remember correctly that was rather
> conservatively.

I would beg to differ. Just to simplify the calculation, let's assume
there are not allocations in GTT (in practice there are very few, so
it's very close to the reality). If you take the memory used by all
VRAM buffers in CS, the limit for that is "VRAM size + (GTT size *
0.7)".

If you have 4GB VRAM and 4GB GTT, Mesa allows per-CS VRAM usage to be 6.8 GB.

If you have any GTT buffers there, you just subtract from that. For
example, if you have 100MB GTT usage, the VRAM limit is 6.7 GB.

Does that sound conservative to you?

Code:
https://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/drivers/radeon/r600_cs.h#n36

Marek