From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f46.google.com (mail-wm0-f46.google.com [74.125.82.46]) by dpdk.org (Postfix) with ESMTP id 62B447D3A for ; Wed, 23 Aug 2017 14:06:14 +0200 (CEST) Received: by mail-wm0-f46.google.com with SMTP id l19so14144333wmi.1 for ; Wed, 23 Aug 2017 05:06:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=6wind-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=78CDmcW7EOIriwQZkOlUtgtYp32Q8mkD09TdMXuWbZo=; b=w9zCZNKW5K8DvVuv/P9hDKBkMPxe7JEWLs91RSOKcPL9A5wROBQcQKy5ZY+ongqrmi W2XgLuze2wO4wxCyu6ru60c+fGAp8yQ46iHLWENFJ+mEduWn0hq0xUT0Wy6Yecdw8/sB 5YA6zF7/gI+pi4RqMbNZuj2bzj//jn7+4b48ooTQYrUraVrkuNzMxNuzR9cEffa+KHpm VFE9d3mLsGeW6/ieu8MZ1S2ToNgzE19ptzjtJ/sprnAd21ajCISZTkcQmeAF023wptm9 X2QdhwmhALRMOUJGO2iAg9iqxjTXSE/6L5kA4zDgx2BiMXxnyG8S75JGxbBE7+lcA0sn lqCA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=78CDmcW7EOIriwQZkOlUtgtYp32Q8mkD09TdMXuWbZo=; b=ifQfBfaS8rZl7c29KAU9aytjxmuK9M9IEkrES/BNrTMxHxM4Ov57EkY1OvmHxZ421D DWXG/MY/DH2Fnt3tAvLR8EQrevlR6Vl7XYfXvOcU5kc6n3NuBDnX+3Qe79fglm+Xu6KZ YB6JV2Ns9MlslhIjKWUC6MHzKEB/yGvMp7XCwPDYsPLp6Mwkeew6a9eR8Wqcw/iU6c7X PXB///M+fNDfI5YL7KMrYH0q6QE8RFxA1jSiknaDEGpQv5kD9PJt7TGKvLHA88HTJwIJ iCBf+MA4vaJg7m/FJ+VCNJEEqEyHv4RGUd5/A0UbUWgVqJMB1mn2IjEEmMlhbg/0jNLj Tmmw== X-Gm-Message-State: AHYfb5gGeLiRB0j0gZLaKOKkIoeuNuOCIGoc7tSuMiwKaObiqFePvQE5 Q1sBwasfECdMxBDxoXYv3w== X-Received: by 10.28.236.150 with SMTP id h22mr1942299wmi.166.1503489973936; Wed, 23 Aug 2017 05:06:13 -0700 (PDT) Received: from autoinstall.dev.6wind.com (host.78.145.23.62.rev.coltfrance.com. [62.23.145.78]) by smtp.gmail.com with ESMTPSA id u1sm1559286wrd.16.2017.08.23.05.06.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 23 Aug 2017 05:06:13 -0700 (PDT) Date: Wed, 23 Aug 2017 14:06:04 +0200 From: =?iso-8859-1?Q?N=E9lio?= Laranjeiro To: Ferruh Yigit Cc: Sagi Grimberg , dev@dpdk.org, Adrien Mazarguil , Shahaf Shuler Message-ID: <20170823120604.GX12995@autoinstall.dev.6wind.com> References: <1503301622-14220-1-git-send-email-sagi@grimberg.me> <1503301622-14220-3-git-send-email-sagi@grimberg.me> <38d6d1e6-7e39-e0d6-863c-2b616f7cbe18@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <38d6d1e6-7e39-e0d6-863c-2b616f7cbe18@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Subject: Re: [dpdk-dev] [PATCH 2/2] net/mlx5: don't map doorbell register to write combining X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 23 Aug 2017 12:06:14 -0000 On Wed, Aug 23, 2017 at 12:03:39PM +0100, Ferruh Yigit wrote: > On 8/21/2017 8:47 AM, Sagi Grimberg wrote: > > 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); > > Although technically this is possible, I wonder how good idea it is a > driver communicating with other processes via system environment variable? We don't have such flexibility though verbs, those environment variable are read by libmlx5 code and the PMD is linked though libibverbs which does not provide a "clean" way tweak libmlx5. It is not used to communicate with another process, it is the same process executing the code which reads those environment variables. Currently it is the only solution we have. For the patch: Acked-by: Nelio Laranjeiro Thanks, -- Nélio Laranjeiro 6WIND