[PATCH] drm/ttm: Don't evict BOs outside of the requested placement range

[Alan Swanson]

On 2014-10-09 07:02, Michel Dänzer wrote:
> From: Michel Dänzer <michel.daenzer at amd.com>
> 
> The radeon driver uses placement range restrictions for several 
> reasons,
> in particular to make sure BOs in VRAM can be accessed by the CPU, e.g.
> during a page fault.
> 
> Without this change, TTM could evict other BOs while trying to satisfy
> the requested placement, even if the evicted BOs were outside of the
> requested placement range. Doing so didn't free up any space in the
> requested placement range, so the (potentially high) eviction cost was
> incurred for no benefit.
> 
> Nominating for stable because radeon driver changes in 3.17 made this
> much more noticeable than before.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=84662
> Cc: stable at vger.kernel.org
> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
> ---
>  drivers/gpu/drm/ttm/ttm_bo.c | 20 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c 
> b/drivers/gpu/drm/ttm/ttm_bo.c
> index 8f5cec6..407fa2d 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -709,6 +709,7 @@ out:
> 
>  static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
>  				uint32_t mem_type,
> +				const struct ttm_place *place,
>  				bool interruptible,
>  				bool no_wait_gpu)
>  {
> @@ -720,8 +721,21 @@ static int ttm_mem_evict_first(struct 
> ttm_bo_device *bdev,
>  	spin_lock(&glob->lru_lock);
>  	list_for_each_entry(bo, &man->lru, lru) {
>  		ret = __ttm_bo_reserve(bo, false, true, false, NULL);
> -		if (!ret)
> +		if (!ret) {
> +			if (place && (place->fpfn || place->lpfn)) {
> +				/* Don't evict this BO if it's outside of the
> +				 * requested placement range
> +				 */
> +				if (place->fpfn >= (bo->mem.start + bo->mem.size) ||
> +				    (place->lpfn && place->lpfn <= bo->mem.start)) {
> +					__ttm_bo_unreserve(bo);
> +					ret = -EBUSY;
> +					continue;
> +				}
> +			}
> +
>  			break;
> +		}
>  	}
> 
>  	if (ret) {
> @@ -782,7 +796,7 @@ static int ttm_bo_mem_force_space(struct
> ttm_buffer_object *bo,
>  			return ret;
>  		if (mem->mm_node)
>  			break;
> -		ret = ttm_mem_evict_first(bdev, mem_type,
> +		ret = ttm_mem_evict_first(bdev, mem_type, place,
>  					  interruptible, no_wait_gpu);
>  		if (unlikely(ret != 0))
>  			return ret;
> @@ -1233,7 +1247,7 @@ static int ttm_bo_force_list_clean(struct
> ttm_bo_device *bdev,
>  	spin_lock(&glob->lru_lock);
>  	while (!list_empty(&man->lru)) {
>  		spin_unlock(&glob->lru_lock);
> -		ret = ttm_mem_evict_first(bdev, mem_type, false, false);
> +		ret = ttm_mem_evict_first(bdev, mem_type, NULL, false, false);
>  		if (ret) {
>  			if (allow_errors) {
>  				return ret;

I believe you need to "s/place/placement/" over this patch.

-- 
Alan.