Re: [PATCH 2/6] drm/ttm: add resource iterator v3

[Felix Kuehling <felix.kuehling@amd.com>]

On 2022-02-15 12:22, Christian König wrote:
> Instead of duplicating that at different places add an iterator over all
> the resources in a resource manager.
>
> v2: add lockdep annotation and kerneldoc
> v3: fix various bugs pointed out by Felix
>
> Signed-off-by: Christian König <christian.koenig@amd.com>
> Tested-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v3)
> ---
>   drivers/gpu/drm/ttm/ttm_bo.c       | 42 ++++++++++--------------
>   drivers/gpu/drm/ttm/ttm_device.c   | 26 +++++++--------
>   drivers/gpu/drm/ttm/ttm_resource.c | 51 ++++++++++++++++++++++++++++++
>   include/drm/ttm/ttm_resource.h     | 23 ++++++++++++++
>   4 files changed, 102 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index cb0fa932d495..11e698e3374c 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -579,38 +579,30 @@ int ttm_mem_evict_first(struct ttm_device *bdev,
>   			struct ww_acquire_ctx *ticket)
>   {
>   	struct ttm_buffer_object *bo = NULL, *busy_bo = NULL;
> +	struct ttm_resource_cursor cursor;
>   	struct ttm_resource *res;
>   	bool locked = false;
> -	unsigned i;
>   	int ret;
>   
>   	spin_lock(&bdev->lru_lock);
> -	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
> -		list_for_each_entry(res, &man->lru[i], lru) {
> -			bool busy;
> -
> -			bo = res->bo;
> -			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 (!ttm_bo_get_unless_zero(bo)) {
> -				if (locked)
> -					dma_resv_unlock(bo->base.resv);
> -				continue;
> -			}
> -			break;
> +	ttm_resource_manager_for_each_res(man, &cursor, res) {
> +		bool busy;
> +
> +		if (!ttm_bo_evict_swapout_allowable(res->bo, ctx, place,
> +						    &locked, &busy)) {
> +			if (busy && !busy_bo && ticket !=
> +			    dma_resv_locking_ctx(res->bo->base.resv))
> +				busy_bo = res->bo;
> +			continue;
>   		}
>   
> -		/* If the inner loop terminated early, we have our candidate */
> -		if (&res->lru != &man->lru[i])
> -			break;
> -
> -		bo = NULL;
> +		if (!ttm_bo_get_unless_zero(res->bo)) {

Just an unrelated nit-pick: If you invert the logic of this if, the loop 
behaves more like a normal loop (without a break at the very end, and 
one less continue statement):

    if (ttm_bo_get_unless_zero(res->bo)) {
         bo = res->bo;
         break;
    }
    if (locked)
         dma_resv_unlock(res->bo->base.resv);

Either way, the patch is

Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>


> +			if (locked)
> +				dma_resv_unlock(res->bo->base.resv);
> +			continue;
> +		}
> +		bo = res->bo;
> +		break;
>   	}
>   
>   	if (!bo) {
> diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
> index ba35887147ba..a0562ab386f5 100644
> --- a/drivers/gpu/drm/ttm/ttm_device.c
> +++ b/drivers/gpu/drm/ttm/ttm_device.c
> @@ -142,10 +142,10 @@ EXPORT_SYMBOL(ttm_global_swapout);
>   int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
>   		       gfp_t gfp_flags)
>   {
> +	struct ttm_resource_cursor cursor;
>   	struct ttm_resource_manager *man;
> -	struct ttm_buffer_object *bo;
>   	struct ttm_resource *res;
> -	unsigned i, j;
> +	unsigned i;
>   	int ret;
>   
>   	spin_lock(&bdev->lru_lock);
> @@ -154,20 +154,16 @@ int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
>   		if (!man || !man->use_tt)
>   			continue;
>   
> -		for (j = 0; j < TTM_MAX_BO_PRIORITY; ++j) {
> -			list_for_each_entry(res, &man->lru[j], lru) {
> -				uint32_t num_pages;
> -
> -				bo = res->bo;
> -				num_pages = PFN_UP(bo->base.size);
> +		ttm_resource_manager_for_each_res(man, &cursor, res) {
> +			struct ttm_buffer_object *bo = res->bo;
> +			uint32_t num_pages = PFN_UP(bo->base.size);
>   
> -				ret = ttm_bo_swapout(bo, ctx, gfp_flags);
> -				/* ttm_bo_swapout has dropped the lru_lock */
> -				if (!ret)
> -					return num_pages;
> -				if (ret != -EBUSY)
> -					return ret;
> -			}
> +			ret = ttm_bo_swapout(bo, ctx, gfp_flags);
> +			/* ttm_bo_swapout has dropped the lru_lock */
> +			if (!ret)
> +				return num_pages;
> +			if (ret != -EBUSY)
> +				return ret;
>   		}
>   	}
>   	spin_unlock(&bdev->lru_lock);
> diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
> index 3af788dd197e..88fc96c315b8 100644
> --- a/drivers/gpu/drm/ttm/ttm_resource.c
> +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> @@ -385,6 +385,57 @@ void ttm_resource_manager_debug(struct ttm_resource_manager *man,
>   }
>   EXPORT_SYMBOL(ttm_resource_manager_debug);
>   
> +/**
> + * ttm_resource_manager_first
> + *
> + * @man: resource manager to iterate over
> + * @cursor: cursor to record the position
> + *
> + * Returns the first resource from the resource manager.
> + */
> +struct ttm_resource *
> +ttm_resource_manager_first(struct ttm_resource_manager *man,
> +			   struct ttm_resource_cursor *cursor)
> +{
> +	struct ttm_resource *res;
> +
> +	lockdep_assert_held(&man->bdev->lru_lock);
> +
> +	for (cursor->priority = 0; cursor->priority < TTM_MAX_BO_PRIORITY;
> +	     ++cursor->priority)
> +		list_for_each_entry(res, &man->lru[cursor->priority], lru)
> +			return res;
> +
> +	return NULL;
> +}
> +
> +/**
> + * ttm_resource_manager_next
> + *
> + * @man: resource manager to iterate over
> + * @cursor: cursor to record the position
> + * @res: the current resource pointer
> + *
> + * Returns the next resource from the resource manager.
> + */
> +struct ttm_resource *
> +ttm_resource_manager_next(struct ttm_resource_manager *man,
> +			  struct ttm_resource_cursor *cursor,
> +			  struct ttm_resource *res)
> +{
> +	lockdep_assert_held(&man->bdev->lru_lock);
> +
> +	list_for_each_entry_continue(res, &man->lru[cursor->priority], lru)
> +		return res;
> +
> +	for (++cursor->priority; cursor->priority < TTM_MAX_BO_PRIORITY;
> +	     ++cursor->priority)
> +		list_for_each_entry(res, &man->lru[cursor->priority], lru)
> +			return res;
> +
> +	return NULL;
> +}
> +
>   static void ttm_kmap_iter_iomap_map_local(struct ttm_kmap_iter *iter,
>   					  struct dma_buf_map *dmap,
>   					  pgoff_t i)
> diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
> index 181e82e3d806..ef0ec700e896 100644
> --- a/include/drm/ttm/ttm_resource.h
> +++ b/include/drm/ttm/ttm_resource.h
> @@ -184,6 +184,17 @@ struct ttm_resource {
>   	struct list_head lru;
>   };
>   
> +/**
> + * struct ttm_resource_cursor
> + *
> + * @priority: the current priority
> + *
> + * Cursor to iterate over the resources in a manager.
> + */
> +struct ttm_resource_cursor {
> +	unsigned int priority;
> +};
> +
>   /**
>    * struct ttm_lru_bulk_move_pos
>    *
> @@ -328,6 +339,18 @@ uint64_t ttm_resource_manager_usage(struct ttm_resource_manager *man);
>   void ttm_resource_manager_debug(struct ttm_resource_manager *man,
>   				struct drm_printer *p);
>   
> +struct ttm_resource *
> +ttm_resource_manager_first(struct ttm_resource_manager *man,
> +			   struct ttm_resource_cursor *cursor);
> +struct ttm_resource *
> +ttm_resource_manager_next(struct ttm_resource_manager *man,
> +			  struct ttm_resource_cursor *cursor,
> +			  struct ttm_resource *res);
> +
> +#define ttm_resource_manager_for_each_res(man, cursor, res)		\
> +	for (res = ttm_resource_manager_first(man, cursor); res;	\
> +	     res = ttm_resource_manager_next(man, cursor, res))
> +
>   struct ttm_kmap_iter *
>   ttm_kmap_iter_iomap_init(struct ttm_kmap_iter_iomap *iter_io,
>   			 struct io_mapping *iomap,