This is a note to let you know that I've just added the patch titled

net/mlx5e: Set EQE based as default TX interrupt moderation mode

to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: net-mlx5e-set-eqe-based-as-default-tx-interrupt-moderation-mode.patch and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Tue Apr 10 23:19:36 CEST 2018

From: Tal Gilboa talgi@mellanox.com Date: Fri, 30 Mar 2018 15:50:08 -0700 Subject: net/mlx5e: Set EQE based as default TX interrupt moderation mode

From: Tal Gilboa talgi@mellanox.com

[ Upstream commit 48bfc39791b8b4a25f165e711f18b9c1617cefbc ]

The default TX moderation mode was mistakenly set to CQE based. The intention was to add a control ability in order to improve some specific use-cases. In general, we prefer to use EQE based moderation as it gives much better numbers for the common cases.

CQE based causes a degradation in the common case since it resets the moderation timer on CQE generation. This causes an issue when TSO is well utilized (large TSO sessions). The timer is set to 16us so traffic of ~64KB TSO sessions per second would mean timer reset (CQE per TSO session -> long time between CQEs). In this case we quickly reach the tcp_limit_output_bytes (256KB by default) and cause a halt in TX traffic.

By setting EQE based moderation we make sure timer would expire after 16us regardless of the packet rate. This fixes an up to 40% packet rate and up to 23% bandwidth degradtions.

Fixes: 0088cbbc4b66 ("net/mlx5e: Enable CQE based moderation on TX CQ") Signed-off-by: Tal Gilboa talgi@mellanox.com Signed-off-by: Saeed Mahameed saeedm@mellanox.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c @@ -4075,7 +4075,7 @@ void mlx5e_build_nic_params(struct mlx5_ struct mlx5e_params *params, u16 max_channels) { - u8 cq_period_mode = 0; + u8 rx_cq_period_mode; u32 link_speed = 0; u32 pci_bw = 0;

@@ -4111,12 +4111,12 @@ void mlx5e_build_nic_params(struct mlx5_ params->lro_timeout = mlx5e_choose_lro_timeout(mdev, MLX5E_DEFAULT_LRO_TIMEOUT);

/* CQ moderation params */ - cq_period_mode = MLX5_CAP_GEN(mdev, cq_period_start_from_cqe) ? + rx_cq_period_mode = MLX5_CAP_GEN(mdev, cq_period_start_from_cqe) ? MLX5_CQ_PERIOD_MODE_START_FROM_CQE : MLX5_CQ_PERIOD_MODE_START_FROM_EQE; params->rx_am_enabled = MLX5_CAP_GEN(mdev, cq_moderation); - mlx5e_set_rx_cq_mode_params(params, cq_period_mode); - mlx5e_set_tx_cq_mode_params(params, cq_period_mode); + mlx5e_set_rx_cq_mode_params(params, rx_cq_period_mode); + mlx5e_set_tx_cq_mode_params(params, MLX5_CQ_PERIOD_MODE_START_FROM_EQE);

/* TX inline */ params->tx_max_inline = mlx5e_get_max_inline_cap(mdev);

Patches currently in stable-queue which might be from talgi@mellanox.com are

queue-4.15/net-mlx5e-set-eqe-based-as-default-tx-interrupt-moderation-mode.patch