[PATCH 3/9] drm/amdgpu: Don't force BOs into visible VRAM for page faults

[Michel Dänzer]

On 24/06/17 02:39 AM, John Brooks wrote:
> There is no need for page faults to force BOs into visible VRAM if it's
> full, and the time it takes to do so is great enough to cause noticeable
> stuttering. Add GTT as a possible placement so that if visible VRAM is
> full, page faults move BOs to GTT instead of evicting other BOs from VRAM.
> 
> Signed-off-by: John Brooks <john at fastquake.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> index 244a7d3..751bc05 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> @@ -981,10 +981,11 @@ int amdgpu_bo_fault_reserve_notify(struct ttm_buffer_object *bo)
>  
>  	/* hurrah the memory is not visible ! */
>  	atomic64_inc(&adev->num_vram_cpu_page_faults);
> -	amdgpu_ttm_placement_from_domain(abo, AMDGPU_GEM_DOMAIN_VRAM);
> +	amdgpu_ttm_placement_from_domain(abo, AMDGPU_GEM_DOMAIN_VRAM |
> +					 AMDGPU_GEM_DOMAIN_GTT);
>  	lpfn =	adev->mc.visible_vram_size >> PAGE_SHIFT;
>  	for (i = 0; i < abo->placement.num_placement; i++) {
> -		/* Force into visible VRAM */
> +		/* Try to move the BO into visible VRAM */
>  		if ((abo->placements[i].flags & TTM_PL_FLAG_VRAM) &&
>  		    (!abo->placements[i].lpfn ||
>  		     abo->placements[i].lpfn > lpfn))
> @@ -993,16 +994,13 @@ int amdgpu_bo_fault_reserve_notify(struct ttm_buffer_object *bo)
>  	abo->placement.busy_placement = abo->placement.placement;
>  	abo->placement.num_busy_placement = abo->placement.num_placement;
>  	r = ttm_bo_validate(bo, &abo->placement, false, false);
> -	if (unlikely(r == -ENOMEM)) {
> -		amdgpu_ttm_placement_from_domain(abo, AMDGPU_GEM_DOMAIN_GTT);
> -		return ttm_bo_validate(bo, &abo->placement, false, false);
> -	} else if (unlikely(r != 0)) {
> +	if (unlikely(r != 0))
>  		return r;
> -	}
>  
>  	offset = bo->mem.start << PAGE_SHIFT;
>  	/* this should never happen */
> -	if ((offset + size) > adev->mc.visible_vram_size)
> +	if (bo->mem.mem_type == TTM_PL_VRAM &&
> +	    (offset + size) > adev->mc.visible_vram_size)
>  		return -EINVAL;
>  
>  	return 0;
> 

AFAICT this is essentially the same as
https://patchwork.freedesktop.org/patch/156993/ . I retracted that patch
due to it causing Rally Dirt performance degradation for Marek.
Presumably other patches in this series compensate for that, but at the
least this patch should be moved to the end of the series.


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