From 9ac936276f8628ef5765bcc2ca7138a803de8aff Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 30 Sep 2021 17:52:49 -0700 Subject: net/mlx4_en: avoid one cache line miss to ring doorbell This patch caches doorbell address directly in struct mlx4_en_tx_ring. This removes the need to bring in cpu caches whole struct mlx4_uar in fast path. Note that mlx4_uar is not guaranteed to be on a local node, because mlx4_bf_alloc() uses a single free list (priv->bf_list) regardless of its node parameter. This kind of change does matter in presence of light/moderate traffic. In high stress, this read-only line would be kept hot in caches. Signed-off-by: Eric Dumazet Cc: Tariq Toukan Reviewed-by: Tariq Toukan Signed-off-by: David S. Miller --- drivers/net/ethernet/mellanox/mlx4/en_tx.c | 4 ++-- drivers/net/ethernet/mellanox/mlx4/mlx4_en.h | 1 + 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c index c56b9dba4c71..817f4154b86d 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c @@ -130,6 +130,7 @@ int mlx4_en_create_tx_ring(struct mlx4_en_priv *priv, ring->bf_enabled = !!(priv->pflags & MLX4_EN_PRIV_FLAGS_BLUEFLAME); } + ring->doorbell_address = ring->bf.uar->map + MLX4_SEND_DOORBELL; ring->hwtstamp_tx_type = priv->hwtstamp_config.tx_type; ring->queue_index = queue_index; @@ -753,8 +754,7 @@ void mlx4_en_xmit_doorbell(struct mlx4_en_tx_ring *ring) #else iowrite32be( #endif - (__force u32)ring->doorbell_qpn, - ring->bf.uar->map + MLX4_SEND_DOORBELL); + (__force u32)ring->doorbell_qpn, ring->doorbell_address); } static void mlx4_en_tx_write_desc(struct mlx4_en_tx_ring *ring, diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h index ad0a8b488832..e132ff4c82f2 100644 --- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h +++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h @@ -283,6 +283,7 @@ struct mlx4_en_tx_ring { struct mlx4_bf bf; /* Following part should be mostly read */ + void __iomem *doorbell_address; __be32 doorbell_qpn; __be32 mr_key; u32 size; /* number of TXBBs */ -- cgit