netdev - [PATCH RFC] net/mlx5_en: switch to Toeplitz RSS hash by default

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Date:   Fri, 31 Aug 2018 14:29:16 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     netdev@...r.kernel.org, Saeed Mahameed <saeedm@...lanox.com>,
        Gal Pressman <galp@...lanox.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: [PATCH RFC] net/mlx5_en: switch to Toeplitz RSS hash by default

XOR (MLX5_RX_HASH_FN_INVERTED_XOR8) gives only 8 bits.
It seems not enough for RFS. All other drivers use toeplitz.

Driver mlx4_en uses Toeplitz by default and warns if hash XOR is used
together with NETIF_F_RXHASH (enabled by default too): "Enabling both
XOR Hash function and RX Hashing can limit RPS functionality".

XOR is default in mlx5_en since commit 2be6967cdbc9
("net/mlx5e: Support ETH_RSS_HASH_XOR").

Hash function could be set via ethtool. But it would be nice to have
single standard for drivers or proper description why this one is special.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 5a7939e70190..def9fb5dcbff 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -4558,7 +4558,7 @@ void mlx5e_build_nic_params(struct mlx5_core_dev *mdev,
 	params->tx_min_inline_mode = mlx5e_params_calculate_tx_min_inline(mdev);
 
 	/* RSS */
-	params->rss_hfunc = ETH_RSS_HASH_XOR;
+	params->rss_hfunc = ETH_RSS_HASH_TOP;
 	netdev_rss_key_fill(params->toeplitz_hash_key, sizeof(params->toeplitz_hash_key));
 	mlx5e_build_default_indir_rqt(params->indirection_rqt,
 				      MLX5E_INDIR_RQT_SIZE, max_channels);