From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <thomas.monjalon@6wind.com> Received: from mail-wm0-f48.google.com (mail-wm0-f48.google.com [74.125.82.48]) by dpdk.org (Postfix) with ESMTP id B7458275D for <dev@dpdk.org>; Tue, 23 Aug 2016 11:31:33 +0200 (CEST) Received: by mail-wm0-f48.google.com with SMTP id o80so185182162wme.1 for <dev@dpdk.org>; Tue, 23 Aug 2016 02:31:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=6wind-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:user-agent:in-reply-to :references:mime-version:content-transfer-encoding; bh=clZ+DEHd45bYc190adRoxKeLxQ5ZYdCNzGIwqYjrusA=; b=a5afPc8q2uF4pHmhw6CQu2RYpWxQc+wGJFJlTPxp8GACiN2TBrvDk/3lkT85Y5jsiU hWg78x9edDz36r0JFNfXLeEeqTcYiRETszG6blORx6/0cCmhU8sssNWd3f7WlMG0KJwX RGgBKcJipBgqV0tTWb6Fu2dw/gWptDMG48Hc+6dM2PxKjPeGIO3tX2TGHDiwQ9Xr6o/I JVPWdYegnucb1yzPjbiP8Lxh4PrOLTzpzcbTnVehS0sAWWl+aR/yVsKd2IdRugyGoMuX kM+jr2ojHEsh7qzEqm783mV6eanSHaxr5YASJFm4e33Oyesy5pR1o65Xw9A2gDC06mry lMHw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:user-agent :in-reply-to:references:mime-version:content-transfer-encoding; bh=clZ+DEHd45bYc190adRoxKeLxQ5ZYdCNzGIwqYjrusA=; b=GP591sMzEk5k4fcji4/sjcekFr9aYcrYBYTReelcgLV+sWTGF5YZ6i2yh/VZVqnVPF 2GmznwE1kzeGdsucvDkcwyS8I+KY3rWx2jJEAN6JK7JtzPjBguvm+IK+JppyPybwJ0su 4/LXZVUUBatBUoSSTrmC8f+cm+ErpVTdfuPfaaF2Mewxoj7cV/l4+aSj3meGOCGUxOZz K9QTd8Epdruyvfz8bKB8F1+SDaxm8qZ6hMZ7lGJcS6dXjDC/wUgTAS23MgGtIQQLpSPm B7oyuPuWUBX0TznaUThcE7zoKOhuRWVvbK4eMZWTNd45EcCqB7lgoaQIpfXWjcbZvv2Y 46mQ== X-Gm-Message-State: AEkooutRIbSWhyruor/rfilk5spa3OcCf23+4lmPdY4KhX6qFBteNlHyQ/bE3eko0K+tWWDY X-Received: by 10.194.127.37 with SMTP id nd5mr20803365wjb.156.1471944693549; Tue, 23 Aug 2016 02:31:33 -0700 (PDT) Received: from xps13.localnet (171.17.90.79.rev.sfr.net. [79.90.17.171]) by smtp.gmail.com with ESMTPSA id f10sm2740645wje.14.2016.08.23.02.31.29 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 23 Aug 2016 02:31:32 -0700 (PDT) From: Thomas Monjalon <thomas.monjalon@6wind.com> To: Yuanhan Liu <yuanhan.liu@linux.intel.com> Cc: dev@dpdk.org, Maxime Coquelin <maxime.coquelin@redhat.com> Date: Tue, 23 Aug 2016 11:31:08 +0200 Message-ID: <2052249.1FX31XPDFZ@xps13> User-Agent: KMail/4.14.10 (Linux/4.5.4-1-ARCH; KDE/4.14.11; x86_64; ; ) In-Reply-To: <1471939839-29778-7-git-send-email-yuanhan.liu@linux.intel.com> References: <1471939839-29778-1-git-send-email-yuanhan.liu@linux.intel.com> <1471939839-29778-7-git-send-email-yuanhan.liu@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Subject: Re: [dpdk-dev] [PATCH 6/6] examples/vhost: add an option to enable Tx zero copy X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK <dev.dpdk.org> List-Unsubscribe: <http://dpdk.org/ml/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://dpdk.org/ml/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <http://dpdk.org/ml/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> X-List-Received-Date: Tue, 23 Aug 2016 09:31:33 -0000 2016-08-23 16:10, Yuanhan Liu: > One thing worth noting while using Tx zero copy is the nb_tx_desc has > to be small enough so that the eth driver will hit the mbuf free > threshold easily and thus free mbuf more frequently. > > The reason behind that is, when Tx zero copy is enabled, guest Tx used > vring will be updated only when corresponding mbuf is freed. If mbuf is > not freed frequently, the guest Tx vring could be starved. I think you should explain this behaviour in the doc of the vhost flag.