linux-kernel - [PATCH 3.16 241/306] IB/mlx5: Use cache line size to select CQE stride

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Date:   Wed, 15 Feb 2017 22:41:40 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Maor Gottlieb" <maorg@...lanox.com>,
        "Leon Romanovsky" <leon@...nel.org>,
        "Daniel Jurgens" <danielj@...lanox.com>,
        "Doug Ledford" <dledford@...hat.com>
Subject: [PATCH 3.16 241/306] IB/mlx5: Use cache line size to select CQE
 stride

3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Jurgens <danielj@...lanox.com>

commit 16b0e0695a73b68d8ca40288c8f9614ef208917b upstream.

When creating kernel CQs use 128B CQE stride if the
cache line size is 128B, 64B otherwise.  This prevents
multiple CQEs from residing in a 128B cache line,
which can cause retries when there are concurrent
read and writes in one cache line.

Tested with IPoIB on PPC64, saw ~5% throughput
improvement.

Fixes: e126ba97dba9 ('mlx5: Add driver for Mellanox Connect-IB adapters')
Signed-off-by: Daniel Jurgens <danielj@...lanox.com>
Signed-off-by: Maor Gottlieb <maorg@...lanox.com>
Signed-off-by: Leon Romanovsky <leon@...nel.org>
Signed-off-by: Doug Ledford <dledford@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/infiniband/hw/mlx5/cq.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/infiniband/hw/mlx5/cq.c
+++ b/drivers/infiniband/hw/mlx5/cq.c
@@ -771,8 +771,7 @@ struct ib_cq *mlx5_ib_create_cq(struct i
 		if (err)
 			goto err_create;
 	} else {
-		/* for now choose 64 bytes till we have a proper interface */
-		cqe_size = 64;
+		cqe_size = cache_line_size() == 128 ? 128 : 64;
 		err = create_cq_kernel(dev, cq, entries, cqe_size, &cqb,
 				       &index, &inlen);
 		if (err)