[PATCH 1/3] drm/amdgpu: add AMDGPU_GEM_CREATE_DISCARDABLE

[Marek Olšák]

OK that sounds good.

Marek

On Wed, May 11, 2022 at 2:04 AM Christian König <
ckoenig.leichtzumerken at gmail.com> wrote:

> Hi Marek,
>
> Am 10.05.22 um 22:43 schrieb Marek Olšák:
>
> A better flag name would be:
> AMDGPU_GEM_CREATE_BEST_PLACEMENT_OR_DISCARD
>
>
> A bit long for my taste and I think the best placement is just a side
> effect.
>
>
> Marek
>
> On Tue, May 10, 2022 at 4:13 PM Marek Olšák <maraeo at gmail.com> wrote:
>
>> Does this really guarantee VRAM placement? The code doesn't say anything
>> about that.
>>
>
> Yes, see the code here:
>
>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>> index 8b7ee1142d9a..1944ef37a61e 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>> @@ -567,6 +567,7 @@ int amdgpu_bo_create(struct amdgpu_device *adev,
>>>                 bp->domain;
>>>         bo->allowed_domains = bo->preferred_domains;
>>>         if (bp->type != ttm_bo_type_kernel &&
>>> +           !(bp->flags & AMDGPU_GEM_CREATE_DISCARDABLE) &&
>>>             bo->allowed_domains == AMDGPU_GEM_DOMAIN_VRAM)
>>>                 bo->allowed_domains |= AMDGPU_GEM_DOMAIN_GTT;
>>>
>>
> The only case where this could be circumvented is when you try to allocate
> more than physically available on an APU.
>
> E.g. you only have something like 32 MiB VRAM and request 64 MiB, then the
> GEM code will catch the error and fallback to GTT (IIRC).
>
> Regards,
> Christian.
>
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