Patch "net/mlx5e: Set EQE based as default TX interrupt moderation mode" has been added to the 4.15-stable tree

Patch "net/mlx5e: Set EQE based as default TX interrupt moderation mode" has been added to the 4.15-stable tree

[gregkh]

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;a=summary

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