Re: [PATCH V2 net-next] net/mlx4_en: avoid one cache line miss to ring doorbell

[Tariq Toukan <ttoukan.linux@gmail.com>]

On 10/1/2021 3:52 AM, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> 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 <edumazet@google.com>
> Cc: Tariq Toukan <tariqt@nvidia.com>
> ---
> V2: added __iomem attribute to remove sparse errors (Jakub)
> 
>   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(-)
> 


Thanks for your patch.
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>