[PATCH 3/3] drm/amdgpu: Try evicting from CPU visible to invisible VRAM first

[John Brooks]

On Fri, May 19, 2017 at 10:20:37AM +0900, Michel Dänzer wrote:
> On 19/05/17 12:43 AM, John Brooks wrote:
> > On Thu, May 18, 2017 at 06:08:09PM +0900, Michel Dänzer wrote:
> >> From: Michel Dänzer <michel.daenzer at amd.com>
> >>
> >> In exchange, move BOs with the AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED
> >> flag set to CPU visible VRAM with more force.
> >>
> >> For other BOs, this gives another chance to stay in VRAM if they
> >> happened to lie in the CPU visible part and another BO needs to go
> >> there.
> >>
> >> This should allow BOs to stay in VRAM longer in some cases.
> >>
> >> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
> 
> [...]
> 
> >> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> >> index 57789b860768..d5ed85026542 100644
> >> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> >> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> >> @@ -206,7 +206,34 @@ static void amdgpu_evict_flags(struct ttm_buffer_object *bo,
> >>  		    adev->mman.buffer_funcs_ring &&
> >>  		    adev->mman.buffer_funcs_ring->ready == false) {
> >>  			amdgpu_ttm_placement_from_domain(abo, AMDGPU_GEM_DOMAIN_CPU);
> >> +		} else if (adev->mc.visible_vram_size < adev->mc.real_vram_size) {
> >> +			unsigned fpfn = adev->mc.visible_vram_size >> PAGE_SHIFT;
> >> +			struct drm_mm_node *node = bo->mem.mm_node;
> >> +			unsigned long pages_left;
> >> +
> >> +			for (pages_left = bo->mem.num_pages;
> >> +			     pages_left;
> >> +			     pages_left -= node->size, node++) {
> >> +				if (node->start < fpfn)
> >> +					break;
> >> +			}
> >> +
> >> +			if (!pages_left)
> >> +				goto gtt;
> >> +
> >> +			/* Try evicting to the CPU inaccessible part of VRAM
> >> +			 * first, but only set GTT as busy placement, so this
> >> +			 * BO will be evicted to GTT rather than causing other
> >> +			 * BOs to be evicted from VRAM
> >> +			 */
> >> +			amdgpu_ttm_placement_from_domain(abo, AMDGPU_GEM_DOMAIN_VRAM |
> >> +							 AMDGPU_GEM_DOMAIN_GTT);
> >> +			abo->placements[0].fpfn = fpfn;
> >> +			abo->placements[0].lpfn = 0;
> >> +			abo->placement.busy_placement = &abo->placements[1];
> > 
> > Are you sure you want to hardcode the placements index? It'll be dependent on
> > the order set up in amdgpu_ttm_placement_init.
> 
> Yes, see patch 1. Looping over the placements and testing their contents
> is silly when we know exactly how they were set up. 

Agreed

> Or do you mean this code shouldn't call amdgpu_ttm_placement_from_domain at
> all and just set up the placements itself?

Calling amdgpu_ttm_placement_from_domain makes sense. I was just imagining a
scenario where code like this that makes assumptions about the ordering of
placements in the array would break silently if that order were changed, and
you'd have to go about finding the places where integer literals were used to
address specific placements.

> 
> -- 
> Earthling Michel Dänzer               |               http://www.amd.com
> Libre software enthusiast             |             Mesa and X developer

--
John Brooks