From: Shahaf Shuler <[email protected]> By default, Verbs maps the doorbell register to write combining. Working with write combining is useful for drivers which use blue flame for the doorbell write.
Since mlx5 PMD uses only doorbells and write combining mapping requires an extra memory barrier to flush the doorbell after its write, setting the mapping to un-cached by default. Such change is reduces the max and average round trip latency significantly. Reported-by: Alexander Solganik <[email protected]> Signed-off-by: Shahaf Shuler <[email protected]> Signed-off-by: Yongseok Koh <[email protected]> Signed-off-by: Alexander Solganik <[email protected]> Signed-off-by: Sagi Grimberg <[email protected]> --- drivers/net/mlx5/mlx5.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c index b7e5046325c0..4c2a0b9652e3 100644 --- a/drivers/net/mlx5/mlx5.c +++ b/drivers/net/mlx5/mlx5.c @@ -920,6 +920,8 @@ rte_mlx5_pmd_init(void) * using this PMD, which is not supported in forked processes. */ setenv("RDMAV_HUGEPAGES_SAFE", "1", 1); + /* Don't map UAR to WC if BlueFlame is not used.*/ + setenv("MLX5_SHUT_UP_BF", "1", 1); ibv_fork_init(); rte_pci_register(&mlx5_driver); } -- 2.7.4
