From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sagi Grimberg Subject: [PATCH 2/2] net/mlx5: don't map doorbell register to write combining Date: Mon, 21 Aug 2017 10:47:02 +0300 Message-ID: <1503301622-14220-3-git-send-email-sagi@grimberg.me> References: <1503301622-14220-1-git-send-email-sagi@grimberg.me> Cc: Nelio Laranjeiro , Adrien Mazarguil , Shahaf Shuler To: dev@dpdk.org Return-path: Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) by dpdk.org (Postfix) with ESMTP id A2EBE8CF4 for ; Mon, 21 Aug 2017 09:47:11 +0200 (CEST) In-Reply-To: <1503301622-14220-1-git-send-email-sagi@grimberg.me> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" From: Shahaf Shuler 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 Signed-off-by: Shahaf Shuler Signed-off-by: Yongseok Koh Signed-off-by: Alexander Solganik Signed-off-by: Sagi Grimberg --- 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