[dpdk-dev] [PATCH v2] common/mlx5: fix Rx/Tx queue doorbell record size

[Viacheslav Ovsiienko <viacheslavo@mellanox.com>]

When Rx/Tx queue was being created with DevX the allocated
doorbell record size was only uint64_t. That was definitely
less than size of CPU cacheline and it might have happened the
doorbell records attached to different queues handled by
different cores were allocated within same cacheline. It might
have caused the contention on doorbell record writing.

This patch extends the allocated memory size for doorbell
record to cacheline size.

Fixes: 21cae8580fd0 ("net/mlx5: allocate door-bells via DevX")
Cc: stable@dpdk.org

Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>

---
v2: - rebase
    - clarify commit message, register is replaced with record

 drivers/common/mlx5/mlx5_common.c |  2 +-
 drivers/common/mlx5/mlx5_common.h | 10 ++++++----
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/common/mlx5/mlx5_common.c b/drivers/common/mlx5/mlx5_common.c
index 79cd5ba..193e73b 100644
--- a/drivers/common/mlx5/mlx5_common.c
+++ b/drivers/common/mlx5/mlx5_common.c
@@ -187,7 +187,7 @@ static inline void mlx5_cpu_id(unsigned int level,
 	page->dbr_bitmap[i] |= (UINT64_C(1) << j);
 	page->dbr_count++;
 	*dbr_page = page;
-	return (((i * 64) + j) * sizeof(uint64_t));
+	return (i * CHAR_BIT * sizeof(uint64_t) + j) * MLX5_DBR_SIZE;
 }
 
 /**
diff --git a/drivers/common/mlx5/mlx5_common.h b/drivers/common/mlx5/mlx5_common.h
index 5b9b7bd..ef7b61b 100644
--- a/drivers/common/mlx5/mlx5_common.h
+++ b/drivers/common/mlx5/mlx5_common.h
@@ -214,10 +214,12 @@ enum mlx5_class {
 	MLX5_CLASS_VDPA = RTE_BIT64(1),
 };
 
-#define MLX5_DBR_PAGE_SIZE 4096 /* Must be >= 512. */
-#define MLX5_DBR_SIZE 8
-#define MLX5_DBR_PER_PAGE (MLX5_DBR_PAGE_SIZE / MLX5_DBR_SIZE)
-#define MLX5_DBR_BITMAP_SIZE (MLX5_DBR_PER_PAGE / 64)
+#define MLX5_DBR_SIZE RTE_CACHE_LINE_SIZE
+#define MLX5_DBR_PER_PAGE 64
+/* Must be >= CHAR_BIT * sizeof(uint64_t) */
+#define MLX5_DBR_PAGE_SIZE (MLX5_DBR_PER_PAGE * MLX5_DBR_SIZE)
+/* Page size must be >= 512. */
+#define MLX5_DBR_BITMAP_SIZE (MLX5_DBR_PER_PAGE / (CHAR_BIT * sizeof(uint64_t)))
 
 struct mlx5_devx_dbr_page {
 	/* Door-bell records, must be first member in structure. */
-- 
1.8.3.1