netdev - [PATCH net-next 09/16] net/mlx5e: Optimize the page cache reducing its size 2x

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Date:   Thu, 29 Sep 2022 00:21:49 -0700
From:   Saeed Mahameed <saeed@...nel.org>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     Saeed Mahameed <saeedm@...dia.com>, netdev@...r.kernel.org,
        Tariq Toukan <tariqt@...dia.com>,
        Maxim Mikityanskiy <maximmi@...dia.com>
Subject: [PATCH net-next 09/16] net/mlx5e: Optimize the page cache reducing its size 2x

From: Maxim Mikityanskiy <maximmi@...dia.com>

RX page cache stores dma_info structs, that consist of a pointer to
struct page and a DMA address. In fact, the DMA address is extracted
from struct page using page_pool_get_dma_addr when a page is pushed to
the cache. By moving this call to the point when a page is popped from
the cache, we can avoid storing the DMA address in the cache,
effectively reducing its size by two times without losing any
functionality.

Signed-off-by: Maxim Mikityanskiy <maximmi@...dia.com>
Reviewed-by: Saeed Mahameed <saeedm@...dia.com>
Reviewed-by: Tariq Toukan <tariqt@...dia.com>
Signed-off-by: Saeed Mahameed <saeedm@...dia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en.h      | 2 +-
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 4 +---
 drivers/net/ethernet/mellanox/mlx5/core/en_rx.c   | 8 ++++----
 3 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
index 449c016262f4..6b91fa7f2221 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -630,7 +630,7 @@ struct mlx5e_mpw_info {
 struct mlx5e_page_cache {
 	u32 head;
 	u32 tail;
-	struct mlx5e_dma_info page_cache[MLX5E_CACHE_SIZE];
+	struct page *page_cache[MLX5E_CACHE_SIZE];
 };
 
 struct mlx5e_rq;
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index fbbc2e792c27..b1d8fd08887b 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -830,13 +830,11 @@ static void mlx5e_free_rq(struct mlx5e_rq *rq)
 
 	for (i = rq->page_cache.head; i != rq->page_cache.tail;
 	     i = (i + 1) & (MLX5E_CACHE_SIZE - 1)) {
-		struct mlx5e_dma_info *dma_info = &rq->page_cache.page_cache[i];
-
 		/* 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, dma_info->page, false);
+		mlx5e_page_release_dynamic(rq, rq->page_cache.page_cache[i], false);
 	}
 
 	xdp_rxq_info_unreg(&rq->xdp_rxq);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index de929fde8cc6..b8aa6f843675 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -245,8 +245,7 @@ static inline bool mlx5e_rx_cache_put(struct mlx5e_rq *rq, struct page *page)
 		return false;
 	}
 
-	cache->page_cache[cache->tail].page = page;
-	cache->page_cache[cache->tail].addr = page_pool_get_dma_addr(page);
+	cache->page_cache[cache->tail] = page;
 	cache->tail = tail_next;
 	return true;
 }
@@ -262,12 +261,13 @@ static inline bool mlx5e_rx_cache_get(struct mlx5e_rq *rq,
 		return false;
 	}
 
-	if (page_ref_count(cache->page_cache[cache->head].page) != 1) {
+	if (page_ref_count(cache->page_cache[cache->head]) != 1) {
 		stats->cache_busy++;
 		return false;
 	}
 
-	*dma_info = cache->page_cache[cache->head];
+	dma_info->page = cache->page_cache[cache->head];
+	dma_info->addr = page_pool_get_dma_addr(dma_info->page);
 	cache->head = (cache->head + 1) & (MLX5E_CACHE_SIZE - 1);
 	stats->cache_reuse++;
 
-- 
2.37.3