Re: [PATCH 3/3] drm/ttm: switch to per device LRU lock

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On Thu, Mar 18, 2021 at 08:47:19PM +0800, Christian König wrote:
> Instead of having a global lock.
> 
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c |  8 ++---
>  drivers/gpu/drm/qxl/qxl_release.c      |  5 +--
>  drivers/gpu/drm/ttm/ttm_bo.c           | 49 ++++++++++++--------------
>  drivers/gpu/drm/ttm/ttm_device.c       | 12 +++----
>  drivers/gpu/drm/ttm/ttm_execbuf_util.c |  8 ++---
>  drivers/gpu/drm/ttm/ttm_resource.c     |  9 +++--
>  include/drm/ttm/ttm_bo_driver.h        |  4 +--
>  include/drm/ttm/ttm_device.h           |  4 +--
>  8 files changed, 43 insertions(+), 56 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 9d19078246c8..ae18c0e32347 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -638,15 +638,15 @@ void amdgpu_vm_move_to_lru_tail(struct amdgpu_device *adev,
>  	struct amdgpu_vm_bo_base *bo_base;
>  
>  	if (vm->bulk_moveable) {
> -		spin_lock(&ttm_glob.lru_lock);
> +		spin_lock(&adev->mman.bdev.lru_lock);

Could you please explain why do you want to instead of the global lock?

Thanks,
Ray

>  		ttm_bo_bulk_move_lru_tail(&vm->lru_bulk_move);
> -		spin_unlock(&ttm_glob.lru_lock);
> +		spin_unlock(&adev->mman.bdev.lru_lock);
>  		return;
>  	}
>  
>  	memset(&vm->lru_bulk_move, 0, sizeof(vm->lru_bulk_move));
>  
> -	spin_lock(&ttm_glob.lru_lock);
> +	spin_lock(&adev->mman.bdev.lru_lock);
>  	list_for_each_entry(bo_base, &vm->idle, vm_status) {
>  		struct amdgpu_bo *bo = bo_base->bo;
>  
> @@ -660,7 +660,7 @@ void amdgpu_vm_move_to_lru_tail(struct amdgpu_device *adev,
>  						&bo->shadow->tbo.mem,
>  						&vm->lru_bulk_move);
>  	}
> -	spin_unlock(&ttm_glob.lru_lock);
> +	spin_unlock(&adev->mman.bdev.lru_lock);
>  
>  	vm->bulk_moveable = true;
>  }
> diff --git a/drivers/gpu/drm/qxl/qxl_release.c b/drivers/gpu/drm/qxl/qxl_release.c
> index f5845c96d414..b19f2f00b215 100644
> --- a/drivers/gpu/drm/qxl/qxl_release.c
> +++ b/drivers/gpu/drm/qxl/qxl_release.c
> @@ -426,16 +426,13 @@ void qxl_release_fence_buffer_objects(struct qxl_release *release)
>  		       release->id | 0xf0000000, release->base.seqno);
>  	trace_dma_fence_emit(&release->base);
>  
> -	spin_lock(&ttm_glob.lru_lock);
> -
>  	list_for_each_entry(entry, &release->bos, head) {
>  		bo = entry->bo;
>  
>  		dma_resv_add_shared_fence(bo->base.resv, &release->base);
> -		ttm_bo_move_to_lru_tail(bo, &bo->mem, NULL);
> +		ttm_bo_move_to_lru_tail_unlocked(bo);
>  		dma_resv_unlock(bo->base.resv);
>  	}
> -	spin_unlock(&ttm_glob.lru_lock);
>  	ww_acquire_fini(&release->ticket);
>  }
>  
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index 3673157527ff..2d2ac532987e 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -243,9 +243,9 @@ static int ttm_bo_individualize_resv(struct ttm_buffer_object *bo)
>  		 * reference it any more. The only tricky case is the trylock on
>  		 * the resv object while holding the lru_lock.
>  		 */
> -		spin_lock(&ttm_glob.lru_lock);
> +		spin_lock(&bo->bdev->lru_lock);
>  		bo->base.resv = &bo->base._resv;
> -		spin_unlock(&ttm_glob.lru_lock);
> +		spin_unlock(&bo->bdev->lru_lock);
>  	}
>  
>  	return r;
> @@ -304,7 +304,7 @@ static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
>  
>  		if (unlock_resv)
>  			dma_resv_unlock(bo->base.resv);
> -		spin_unlock(&ttm_glob.lru_lock);
> +		spin_unlock(&bo->bdev->lru_lock);
>  
>  		lret = dma_resv_wait_timeout_rcu(resv, true, interruptible,
>  						 30 * HZ);
> @@ -314,7 +314,7 @@ static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
>  		else if (lret == 0)
>  			return -EBUSY;
>  
> -		spin_lock(&ttm_glob.lru_lock);
> +		spin_lock(&bo->bdev->lru_lock);
>  		if (unlock_resv && !dma_resv_trylock(bo->base.resv)) {
>  			/*
>  			 * We raced, and lost, someone else holds the reservation now,
> @@ -324,7 +324,7 @@ static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
>  			 * delayed destruction would succeed, so just return success
>  			 * here.
>  			 */
> -			spin_unlock(&ttm_glob.lru_lock);
> +			spin_unlock(&bo->bdev->lru_lock);
>  			return 0;
>  		}
>  		ret = 0;
> @@ -333,13 +333,13 @@ static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
>  	if (ret || unlikely(list_empty(&bo->ddestroy))) {
>  		if (unlock_resv)
>  			dma_resv_unlock(bo->base.resv);
> -		spin_unlock(&ttm_glob.lru_lock);
> +		spin_unlock(&bo->bdev->lru_lock);
>  		return ret;
>  	}
>  
>  	ttm_bo_del_from_lru(bo);
>  	list_del_init(&bo->ddestroy);
> -	spin_unlock(&ttm_glob.lru_lock);
> +	spin_unlock(&bo->bdev->lru_lock);
>  	ttm_bo_cleanup_memtype_use(bo);
>  
>  	if (unlock_resv)
> @@ -356,13 +356,12 @@ static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
>   */
>  bool ttm_bo_delayed_delete(struct ttm_device *bdev, bool remove_all)
>  {
> -	struct ttm_global *glob = &ttm_glob;
>  	struct list_head removed;
>  	bool empty;
>  
>  	INIT_LIST_HEAD(&removed);
>  
> -	spin_lock(&glob->lru_lock);
> +	spin_lock(&bdev->lru_lock);
>  	while (!list_empty(&bdev->ddestroy)) {
>  		struct ttm_buffer_object *bo;
>  
> @@ -373,24 +372,24 @@ bool ttm_bo_delayed_delete(struct ttm_device *bdev, bool remove_all)
>  			continue;
>  
>  		if (remove_all || bo->base.resv != &bo->base._resv) {
> -			spin_unlock(&glob->lru_lock);
> +			spin_unlock(&bdev->lru_lock);
>  			dma_resv_lock(bo->base.resv, NULL);
>  
> -			spin_lock(&glob->lru_lock);
> +			spin_lock(&bdev->lru_lock);
>  			ttm_bo_cleanup_refs(bo, false, !remove_all, true);
>  
>  		} else if (dma_resv_trylock(bo->base.resv)) {
>  			ttm_bo_cleanup_refs(bo, false, !remove_all, true);
>  		} else {
> -			spin_unlock(&glob->lru_lock);
> +			spin_unlock(&bdev->lru_lock);
>  		}
>  
>  		ttm_bo_put(bo);
> -		spin_lock(&glob->lru_lock);
> +		spin_lock(&bdev->lru_lock);
>  	}
>  	list_splice_tail(&removed, &bdev->ddestroy);
>  	empty = list_empty(&bdev->ddestroy);
> -	spin_unlock(&glob->lru_lock);
> +	spin_unlock(&bdev->lru_lock);
>  
>  	return empty;
>  }
> @@ -425,7 +424,7 @@ static void ttm_bo_release(struct kref *kref)
>  		ttm_bo_flush_all_fences(bo);
>  		bo->deleted = true;
>  
> -		spin_lock(&ttm_glob.lru_lock);
> +		spin_lock(&bo->bdev->lru_lock);
>  
>  		/*
>  		 * Make pinned bos immediately available to
> @@ -442,17 +441,17 @@ static void ttm_bo_release(struct kref *kref)
>  
>  		kref_init(&bo->kref);
>  		list_add_tail(&bo->ddestroy, &bdev->ddestroy);
> -		spin_unlock(&ttm_glob.lru_lock);
> +		spin_unlock(&bo->bdev->lru_lock);
>  
>  		schedule_delayed_work(&bdev->wq,
>  				      ((HZ / 100) < 1) ? 1 : HZ / 100);
>  		return;
>  	}
>  
> -	spin_lock(&ttm_glob.lru_lock);
> +	spin_lock(&bo->bdev->lru_lock);
>  	ttm_bo_del_from_lru(bo);
>  	list_del(&bo->ddestroy);
> -	spin_unlock(&ttm_glob.lru_lock);
> +	spin_unlock(&bo->bdev->lru_lock);
>  
>  	ttm_bo_cleanup_memtype_use(bo);
>  	dma_resv_unlock(bo->base.resv);
> @@ -626,7 +625,7 @@ int ttm_mem_evict_first(struct ttm_device *bdev,
>  	unsigned i;
>  	int ret;
>  
> -	spin_lock(&ttm_glob.lru_lock);
> +	spin_lock(&bo->bdev->lru_lock);
>  	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
>  		list_for_each_entry(bo, &man->lru[i], lru) {
>  			bool busy;
> @@ -663,7 +662,7 @@ int ttm_mem_evict_first(struct ttm_device *bdev,
>  	if (!bo) {
>  		if (busy_bo && !ttm_bo_get_unless_zero(busy_bo))
>  			busy_bo = NULL;
> -		spin_unlock(&ttm_glob.lru_lock);
> +		spin_unlock(&bo->bdev->lru_lock);
>  		ret = ttm_mem_evict_wait_busy(busy_bo, ctx, ticket);
>  		if (busy_bo)
>  			ttm_bo_put(busy_bo);
> @@ -677,7 +676,7 @@ int ttm_mem_evict_first(struct ttm_device *bdev,
>  		return ret;
>  	}
>  
> -	spin_unlock(&ttm_glob.lru_lock);
> +	spin_unlock(&bo->bdev->lru_lock);
>  
>  	ret = ttm_bo_evict(bo, ctx);
>  	if (locked)
> @@ -777,10 +776,9 @@ static int ttm_bo_mem_placement(struct ttm_buffer_object *bo,
>  	mem->mem_type = place->mem_type;
>  	mem->placement = place->flags;
>  
> -	spin_lock(&ttm_glob.lru_lock);
> +	spin_lock(&bo->bdev->lru_lock);
>  	ttm_bo_move_to_lru_tail(bo, mem, NULL);
> -	spin_unlock(&ttm_glob.lru_lock);
> -
> +	spin_unlock(&bo->bdev->lru_lock);
>  	return 0;
>  }
>  
> @@ -1167,7 +1165,6 @@ 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_global *glob = &ttm_glob;
>  	bool locked;
>  	int ret;
>  
> @@ -1188,7 +1185,7 @@ int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
>  
>  	ttm_bo_del_from_lru(bo);
>  	/* TODO: Cleanup the locking */
> -	spin_unlock(&glob->lru_lock);
> +	spin_unlock(&bo->bdev->lru_lock);
>  
>  	/*
>  	 * Move to system cached
> diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
> index 2096a0fd9c35..85f6975d9872 100644
> --- a/drivers/gpu/drm/ttm/ttm_device.c
> +++ b/drivers/gpu/drm/ttm/ttm_device.c
> @@ -81,7 +81,6 @@ static int ttm_global_init(void)
>  	ttm_pool_mgr_init(num_pages * 50 / 100);
>  	ttm_tt_mgr_init();
>  
> -	spin_lock_init(&glob->lru_lock);
>  	glob->dummy_read_page = alloc_page(__GFP_ZERO | GFP_DMA32);
>  
>  	if (unlikely(glob->dummy_read_page == NULL)) {
> @@ -125,13 +124,12 @@ EXPORT_SYMBOL(ttm_global_swapout);
>  long ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
>  			gfp_t gfp_flags)
>  {
> -	struct ttm_global *glob = &ttm_glob;
>  	struct ttm_resource_manager *man;
>  	struct ttm_buffer_object *bo;
>  	unsigned i, j;
>  	int ret;
>  
> -	spin_lock(&glob->lru_lock);
> +	spin_lock(&bdev->lru_lock);
>  	for (i = TTM_PL_SYSTEM; i < TTM_NUM_MEM_TYPES; ++i) {
>  		man = ttm_manager_type(bdev, i);
>  		if (!man || !man->use_tt)
> @@ -156,7 +154,7 @@ long ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
>  			}
>  		}
>  	}
> -	spin_unlock(&glob->lru_lock);
> +	spin_unlock(&bdev->lru_lock);
>  	return 0;
>  }
>  EXPORT_SYMBOL(ttm_device_swapout);
> @@ -223,6 +221,7 @@ int ttm_device_init(struct ttm_device *bdev, struct ttm_device_funcs *funcs,
>  
>  	bdev->vma_manager = vma_manager;
>  	INIT_DELAYED_WORK(&bdev->wq, ttm_device_delayed_workqueue);
> +	spin_lock_init(&bdev->lru_lock);
>  	INIT_LIST_HEAD(&bdev->ddestroy);
>  	bdev->dev_mapping = mapping;
>  	mutex_lock(&ttm_global_mutex);
> @@ -235,7 +234,6 @@ EXPORT_SYMBOL(ttm_device_init);
>  
>  void ttm_device_fini(struct ttm_device *bdev)
>  {
> -	struct ttm_global *glob = &ttm_glob;
>  	struct ttm_resource_manager *man;
>  	unsigned i;
>  
> @@ -252,11 +250,11 @@ void ttm_device_fini(struct ttm_device *bdev)
>  	if (ttm_bo_delayed_delete(bdev, true))
>  		pr_debug("Delayed destroy list was clean\n");
>  
> -	spin_lock(&glob->lru_lock);
> +	spin_lock(&bdev->lru_lock);
>  	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i)
>  		if (list_empty(&man->lru[0]))
>  			pr_debug("Swap list %d was clean\n", i);
> -	spin_unlock(&glob->lru_lock);
> +	spin_unlock(&bdev->lru_lock);
>  
>  	ttm_pool_fini(&bdev->pool);
>  	ttm_global_release();
> diff --git a/drivers/gpu/drm/ttm/ttm_execbuf_util.c b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> index 690ab97d52b7..071c48d672c6 100644
> --- a/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> @@ -51,14 +51,12 @@ void ttm_eu_backoff_reservation(struct ww_acquire_ctx *ticket,
>  	if (list_empty(list))
>  		return;
>  
> -	spin_lock(&ttm_glob.lru_lock);
>  	list_for_each_entry(entry, list, head) {
>  		struct ttm_buffer_object *bo = entry->bo;
>  
> -		ttm_bo_move_to_lru_tail(bo, &bo->mem, NULL);
> +		ttm_bo_move_to_lru_tail_unlocked(bo);
>  		dma_resv_unlock(bo->base.resv);
>  	}
> -	spin_unlock(&ttm_glob.lru_lock);
>  
>  	if (ticket)
>  		ww_acquire_fini(ticket);
> @@ -154,7 +152,6 @@ void ttm_eu_fence_buffer_objects(struct ww_acquire_ctx *ticket,
>  	if (list_empty(list))
>  		return;
>  
> -	spin_lock(&ttm_glob.lru_lock);
>  	list_for_each_entry(entry, list, head) {
>  		struct ttm_buffer_object *bo = entry->bo;
>  
> @@ -162,10 +159,9 @@ void ttm_eu_fence_buffer_objects(struct ww_acquire_ctx *ticket,
>  			dma_resv_add_shared_fence(bo->base.resv, fence);
>  		else
>  			dma_resv_add_excl_fence(bo->base.resv, fence);
> -		ttm_bo_move_to_lru_tail(bo, &bo->mem, NULL);
> +		ttm_bo_move_to_lru_tail_unlocked(bo);
>  		dma_resv_unlock(bo->base.resv);
>  	}
> -	spin_unlock(&ttm_glob.lru_lock);
>  	if (ticket)
>  		ww_acquire_fini(ticket);
>  }
> diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
> index ed1672a9f332..04f2eef653ab 100644
> --- a/drivers/gpu/drm/ttm/ttm_resource.c
> +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> @@ -91,7 +91,6 @@ int ttm_resource_manager_evict_all(struct ttm_device *bdev,
>  		.no_wait_gpu = false,
>  		.force_alloc = true
>  	};
> -	struct ttm_global *glob = &ttm_glob;
>  	struct dma_fence *fence;
>  	int ret;
>  	unsigned i;
> @@ -100,18 +99,18 @@ int ttm_resource_manager_evict_all(struct ttm_device *bdev,
>  	 * Can't use standard list traversal since we're unlocking.
>  	 */
>  
> -	spin_lock(&glob->lru_lock);
> +	spin_lock(&bdev->lru_lock);
>  	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
>  		while (!list_empty(&man->lru[i])) {
> -			spin_unlock(&glob->lru_lock);
> +			spin_unlock(&bdev->lru_lock);
>  			ret = ttm_mem_evict_first(bdev, man, NULL, &ctx,
>  						  NULL);
>  			if (ret)
>  				return ret;
> -			spin_lock(&glob->lru_lock);
> +			spin_lock(&bdev->lru_lock);
>  		}
>  	}
> -	spin_unlock(&glob->lru_lock);
> +	spin_unlock(&bdev->lru_lock);
>  
>  	spin_lock(&man->move_lock);
>  	fence = dma_fence_get(man->move);
> diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
> index d007feef7676..dbccac957f8f 100644
> --- a/include/drm/ttm/ttm_bo_driver.h
> +++ b/include/drm/ttm/ttm_bo_driver.h
> @@ -180,9 +180,9 @@ static inline int ttm_bo_reserve_slowpath(struct ttm_buffer_object *bo,
>  static inline void
>  ttm_bo_move_to_lru_tail_unlocked(struct ttm_buffer_object *bo)
>  {
> -	spin_lock(&ttm_glob.lru_lock);
> +	spin_lock(&bo->bdev->lru_lock);
>  	ttm_bo_move_to_lru_tail(bo, &bo->mem, NULL);
> -	spin_unlock(&ttm_glob.lru_lock);
> +	spin_unlock(&bo->bdev->lru_lock);
>  }
>  
>  static inline void ttm_bo_assign_mem(struct ttm_buffer_object *bo,
> diff --git a/include/drm/ttm/ttm_device.h b/include/drm/ttm/ttm_device.h
> index cda6efb4c34b..bae56d29e8ff 100644
> --- a/include/drm/ttm/ttm_device.h
> +++ b/include/drm/ttm/ttm_device.h
> @@ -56,7 +56,6 @@ extern struct ttm_global {
>  	 */
>  
>  	struct page *dummy_read_page;
> -	spinlock_t lru_lock;
>  
>  	/**
>  	 * Protected by ttm_global_mutex.
> @@ -277,8 +276,9 @@ struct ttm_device {
>  	struct ttm_pool pool;
>  
>  	/*
> -	 * Protected by the global:lru lock.
> +	 * Protection for the per manager LRU and ddestroy lists.
>  	 */
> +	spinlock_t lru_lock;
>  	struct list_head ddestroy;
>  
>  	/*
> -- 
> 2.25.1
> 
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