Re: [PATCH v2 11/20] drm/amdgpu: round robin through clear_entities in amdgpu_fill_buffer

Christian König
2025-11-17T08:47:53Z

On 11/13/25 17:05, Pierre-Eric Pelloux-Prayer wrote:
> This makes clear of different BOs run in parallel. Partial jobs to
> clear a single BO still execute sequentially.
>
> Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 2 +-
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 9 ++++++++-
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h | 1 +
> 3 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> index be3532134e46..33b397107778 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> @@ -1321,7 +1321,7 @@ void amdgpu_bo_release_notify(struct ttm_buffer_object *bo)
> if (r)
> goto out;
>
> - r = amdgpu_fill_buffer(&adev->mman.clear_entities[0], abo, 0, &bo->base._resv,
> + r = amdgpu_fill_buffer(NULL, abo, 0, &bo->base._resv,
> &fence, NULL, AMDGPU_KERNEL_JOB_ID_CLEAR_ON_RELEASE);
> if (WARN_ON(r))
> goto out;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 411997db70eb..486c701d0d5b 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -2224,6 +2224,7 @@ u32 amdgpu_ttm_set_buffer_funcs_status(struct amdgpu_device *adev, bool enable)
> adev->mman.clear_entities = kcalloc(num_clear_entities,
> sizeof(struct amdgpu_ttm_buffer_entity),
> GFP_KERNEL);
> + atomic_set(&adev->mman.next_clear_entity, 0);
> if (!adev->mman.clear_entities)
> goto error_free_entity;
>
> @@ -2489,7 +2490,7 @@ int amdgpu_fill_buffer(struct amdgpu_ttm_buffer_entity *entity,
> struct amdgpu_ring *ring = adev->mman.buffer_funcs_ring;
> struct dma_fence *fence = NULL;
> struct amdgpu_res_cursor dst;
> - int r;
> + int r, e;
>
> if (!adev->mman.buffer_funcs_enabled) {
> dev_err(adev->dev,
> @@ -2497,6 +2498,12 @@ int amdgpu_fill_buffer(struct amdgpu_ttm_buffer_entity *entity,
> return -EINVAL;
> }
>
> + if (entity == NULL) {
> + e = atomic_inc_return(&adev->mman.next_clear_entity) %
> + adev->mman.num_clear_entities;
> + entity = &adev->mman.clear_entities[e];
> + }
> +

Oh, that is really ugly.

I think you should have something like amdgpu_ttm_next_clear_entity() which returns the pointer round robin.

And then give that as parameter to amdgpu_fill_buffer().

Regards,
Christian.

> amdgpu_res_first(bo->tbo.resource, 0, amdgpu_bo_size(bo), &dst);
>
> mutex_lock(&entity->gart_window_lock);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> index e8f8165f5bcf..781b0bdca56c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> @@ -73,6 +73,7 @@ struct amdgpu_mman {
>
> struct amdgpu_ttm_buffer_entity default_entity; /* has no gart windows */
> struct amdgpu_ttm_buffer_entity *clear_entities;
> + atomic_t next_clear_entity;
> u32 num_clear_entities;
> struct amdgpu_ttm_buffer_entity move_entities[TTM_NUM_MOVE_FENCES];
> u32 num_move_entities;