net/mlx5e: RX, Remove internal page_cache

This patch removes the internal rx page_cache and uses the generic
page_pool api only. It used to be that the page_pool couldn't handle all
the mlx5 driver usecases, but with the introduction of skb recycling and
page fragmentaton in the page_pool full switch can now be made. Some
benfits of this transition:
* Better page recycling in the cases when the page_cache was suffering
  from head of queue blocking. The page_pool doesn't have this issue.
* DMA mapping/unmapping can be managed by the page_pool.
* mlx5e_rq size reduced by more than 50% due to the page_cache array
  being deleted.

This patch only removes the page_cache. Downstream patches will enable
the required page_pool features and will add further fine-tuning.

Signed-off-by: Dragos Tatulea <[email protected]>
Reviewed-by: Tariq Toukan <[email protected]>
Signed-off-by: Saeed Mahameed <[email protected]>

Author: dtatulea

drivers/net/ethernet/mellanox/mlx5/core/en.h

@@ -628,11 +628,6 @@ struct mlx5e_mpw_info {
 #define MLX5E_CACHE_UNIT (MLX5_MPWRQ_MAX_PAGES_PER_WQE > NAPI_POLL_WEIGHT ? \
 			  MLX5_MPWRQ_MAX_PAGES_PER_WQE : NAPI_POLL_WEIGHT)
 #define MLX5E_CACHE_SIZE	(4 * roundup_pow_of_two(MLX5E_CACHE_UNIT))
-struct mlx5e_page_cache {
-	u32 head;
-	u32 tail;
-	struct page *page_cache[MLX5E_CACHE_SIZE];
-};
 
 struct mlx5e_rq;
 typedef void (*mlx5e_fp_handle_rx_cqe)(struct mlx5e_rq*, struct mlx5_cqe64*);
@@ -745,7 +740,6 @@ struct mlx5e_rq {
 	struct mlx5e_rq_stats *stats;
 	struct mlx5e_cq        cq;
 	struct mlx5e_cq_decomp cqd;
-	struct mlx5e_page_cache page_cache;
 	struct hwtstamp_config *tstamp;
 	struct mlx5_clock      *clock;
 	struct mlx5e_icosq    *icosq;

drivers/net/ethernet/mellanox/mlx5/core/en_main.c

@@ -900,9 +900,6 @@ static int mlx5e_alloc_rq(struct mlx5e_params *params,
 		rq->dim.mode = DIM_CQ_PERIOD_MODE_START_FROM_EQE;
 	}
 
-	rq->page_cache.head = 0;
-	rq->page_cache.tail = 0;
-
 	return 0;
 
 err_destroy_page_pool:
@@ -933,7 +930,6 @@ static int mlx5e_alloc_rq(struct mlx5e_params *params,
 static void mlx5e_free_rq(struct mlx5e_rq *rq)
 {
 	struct bpf_prog *old_prog;
-	int i;
 
 	if (xdp_rxq_info_is_reg(&rq->xdp_rxq)) {
 		old_prog = rcu_dereference_protected(rq->xdp_prog,
@@ -953,15 +949,6 @@ static void mlx5e_free_rq(struct mlx5e_rq *rq)
 		mlx5e_free_wqe_alloc_info(rq);
 	}
 
-	for (i = rq->page_cache.head; i != rq->page_cache.tail;
-	     i = (i + 1) & (MLX5E_CACHE_SIZE - 1)) {
-		/* With AF_XDP, page_cache is not used, so this loop is not
-		 * entered, and it's safe to call mlx5e_page_release_dynamic
-		 * directly.
-		 */
-		mlx5e_page_release_dynamic(rq, rq->page_cache.page_cache[i], false);
-	}
-
 	xdp_rxq_info_unreg(&rq->xdp_rxq);
 	page_pool_destroy(rq->page_pool);
 	mlx5_wq_destroy(&rq->wq_ctrl);

drivers/net/ethernet/mellanox/mlx5/core/en_rx.c

@@ -271,60 +271,10 @@ static inline u32 mlx5e_decompress_cqes_start(struct mlx5e_rq *rq,
 	return mlx5e_decompress_cqes_cont(rq, wq, 1, budget_rem);
 }
 
-static inline bool mlx5e_rx_cache_put(struct mlx5e_rq *rq, struct page *page)
-{
-	struct mlx5e_page_cache *cache = &rq->page_cache;
-	u32 tail_next = (cache->tail + 1) & (MLX5E_CACHE_SIZE - 1);
-	struct mlx5e_rq_stats *stats = rq->stats;
-
-	if (tail_next == cache->head) {
-		stats->cache_full++;
-		return false;
-	}
-
-	if (!dev_page_is_reusable(page)) {
-		stats->cache_waive++;
-		return false;
-	}
-
-	cache->page_cache[cache->tail] = page;
-	cache->tail = tail_next;
-	return true;
-}
-
-static inline bool mlx5e_rx_cache_get(struct mlx5e_rq *rq, struct page **pagep)
-{
-	struct mlx5e_page_cache *cache = &rq->page_cache;
-	struct mlx5e_rq_stats *stats = rq->stats;
-	dma_addr_t addr;
-
-	if (unlikely(cache->head == cache->tail)) {
-		stats->cache_empty++;
-		return false;
-	}
-
-	if (page_ref_count(cache->page_cache[cache->head]) != 1) {
-		stats->cache_busy++;
-		return false;
-	}
-
-	*pagep = cache->page_cache[cache->head];
-	cache->head = (cache->head + 1) & (MLX5E_CACHE_SIZE - 1);
-	stats->cache_reuse++;
-
-	addr = page_pool_get_dma_addr(*pagep);
-	/* Non-XSK always uses PAGE_SIZE. */
-	dma_sync_single_for_device(rq->pdev, addr, PAGE_SIZE, rq->buff.map_dir);
-	return true;
-}
-
 static inline int mlx5e_page_alloc_pool(struct mlx5e_rq *rq, struct page **pagep)
 {
 	dma_addr_t addr;
 
-	if (mlx5e_rx_cache_get(rq, pagep))
-		return 0;
-
 	*pagep = page_pool_dev_alloc_pages(rq->page_pool);
 	if (unlikely(!*pagep))
 		return -ENOMEM;
@@ -353,9 +303,6 @@ void mlx5e_page_dma_unmap(struct mlx5e_rq *rq, struct page *page)
 void mlx5e_page_release_dynamic(struct mlx5e_rq *rq, struct page *page, bool recycle)
 {
 	if (likely(recycle)) {
-		if (mlx5e_rx_cache_put(rq, page))
-			return;
-
 		mlx5e_page_dma_unmap(rq, page);
 		page_pool_recycle_direct(rq->page_pool, page);
 	} else {