Op 18-05-2021 om 10:26 schreef Thomas Hellström:
> We are calling the eviction_valuable driver callback at eviction time to
> determine whether we actually can evict a buffer object.
> The upcoming i915 TTM backend needs the same functionality for swapout,
> and that might actually be beneficial to other drivers as well.
>
> Add an eviction_valuable call also in the swapout path. Try to keep the
> current behaviour for all drivers by returning true if the buffer object
> is already in the TTM_PL_SYSTEM placement. We change behaviour for the
> case where a buffer object is in a TT backed placement when swapped out,
> in which case the drivers normal eviction_valuable path is run.
>
> Finally export ttm_tt_unpopulate() and don't swap out bos
> that are not populated. This allows a driver to purge a bo at
> swapout time if its content is no longer valuable rather than to
> have TTM swap the contents out.
>
> Cc: Christian König <christian.koe...@amd.com>
> Signed-off-by: Thomas Hellström <thomas.hellst...@linux.intel.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 4 +++
> drivers/gpu/drm/ttm/ttm_bo.c | 41 +++++++++++++++----------
> drivers/gpu/drm/ttm/ttm_tt.c | 4 +++
> 3 files changed, 33 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 8c7ec09eb1a4..d5a9d7a88315 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -1399,6 +1399,10 @@ static bool amdgpu_ttm_bo_eviction_valuable(struct
> ttm_buffer_object *bo,
> struct dma_fence *f;
> int i;
>
> + /* Swapout? */
> + if (bo->mem.mem_type == TTM_PL_SYSTEM)
> + return true;
> +
> if (bo->type == ttm_bo_type_kernel &&
> !amdgpu_vm_evictable(ttm_to_amdgpu_bo(bo)))
> return false;
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index 4479c55aaa1d..6a3f3112f62a 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -531,6 +531,10 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
> bool ttm_bo_eviction_valuable(struct ttm_buffer_object *bo,
> const struct ttm_place *place)
> {
> + dma_resv_assert_held(bo->base.resv);
> + if (bo->mem.mem_type == TTM_PL_SYSTEM)
> + return true;
> +
> /* Don't evict this BO if it's outside of the
> * requested placement range
> */
> @@ -553,7 +557,9 @@ EXPORT_SYMBOL(ttm_bo_eviction_valuable);
> * b. Otherwise, trylock it.
> */
> static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
> - struct ttm_operation_ctx *ctx, bool *locked, bool *busy)
> + struct ttm_operation_ctx *ctx,
> + const struct ttm_place *place,
> + bool *locked, bool *busy)
> {
> bool ret = false;
>
> @@ -571,6 +577,12 @@ static bool ttm_bo_evict_swapout_allowable(struct
> ttm_buffer_object *bo,
> *busy = !ret;
> }
>
> + if (ret && place && !bo->bdev->funcs->eviction_valuable(bo, place)) {
> + ret = false;
> + if (locked)
> + dma_resv_unlock(bo->base.resv);
> + }
Probably meant to check and clear *locked here?
With that fixed:
Reviewed-by: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
> +
> return ret;
> }
>
> @@ -625,20 +637,14 @@ int ttm_mem_evict_first(struct ttm_device *bdev,
> list_for_each_entry(bo, &man->lru[i], lru) {
> bool busy;
>
> - if (!ttm_bo_evict_swapout_allowable(bo, ctx, &locked,
> - &busy)) {
> + if (!ttm_bo_evict_swapout_allowable(bo, ctx, place,
> + &locked, &busy)) {
> if (busy && !busy_bo && ticket !=
> dma_resv_locking_ctx(bo->base.resv))
> busy_bo = bo;
> continue;
> }
>
> - if (place && !bdev->funcs->eviction_valuable(bo,
> - place)) {
> - if (locked)
> - dma_resv_unlock(bo->base.resv);
> - continue;
> - }
> if (!ttm_bo_get_unless_zero(bo)) {
> if (locked)
> dma_resv_unlock(bo->base.resv);
> @@ -1138,10 +1144,18 @@ EXPORT_SYMBOL(ttm_bo_wait);
> int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx
> *ctx,
> gfp_t gfp_flags)
> {
> + struct ttm_place place = {};
> bool locked;
> int ret;
>
> - if (!ttm_bo_evict_swapout_allowable(bo, ctx, &locked, NULL))
> + /*
> + * While the bo may already reside in SYSTEM placement, set
> + * SYSTEM as new placement to cover also the move further below.
> + * The driver may use the fact that we're moving from SYSTEM
> + * as an indication that we're about to swap out.
> + */
> + place.mem_type = TTM_PL_SYSTEM;
> + if (!ttm_bo_evict_swapout_allowable(bo, ctx, &place, &locked, NULL))
> return -EBUSY;
>
> if (!ttm_bo_get_unless_zero(bo)) {
> @@ -1166,12 +1180,7 @@ int ttm_bo_swapout(struct ttm_buffer_object *bo,
> struct ttm_operation_ctx *ctx,
> if (bo->mem.mem_type != TTM_PL_SYSTEM) {
> struct ttm_operation_ctx ctx = { false, false };
> struct ttm_resource evict_mem;
> - struct ttm_place place, hop;
> -
> - memset(&place, 0, sizeof(place));
> - memset(&hop, 0, sizeof(hop));
> -
> - place.mem_type = TTM_PL_SYSTEM;
> + struct ttm_place hop = {};
>
> ret = ttm_resource_alloc(bo, &place, &evict_mem);
> if (unlikely(ret))
> diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
> index 539e0232cb3b..7878ca4876c5 100644
> --- a/drivers/gpu/drm/ttm/ttm_tt.c
> +++ b/drivers/gpu/drm/ttm/ttm_tt.c
> @@ -258,6 +258,9 @@ int ttm_tt_swapout(struct ttm_device *bdev, struct ttm_tt
> *ttm,
> struct page *to_page;
> int i, ret;
>
> + if (!ttm_tt_is_populated(ttm))
> + return 0;
> +
> swap_storage = shmem_file_setup("ttm swap", size, 0);
> if (IS_ERR(swap_storage)) {
> pr_err("Failed allocating swap storage\n");
> @@ -399,6 +402,7 @@ void ttm_tt_unpopulate(struct ttm_device *bdev, struct
> ttm_tt *ttm)
>
> ttm->page_flags &= ~TTM_PAGE_FLAG_PRIV_POPULATED;
> }
> +EXPORT_SYMBOL(ttm_tt_unpopulate);
>
> #ifdef CONFIG_DEBUG_FS
>
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