From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f179.google.com (mail-ig0-f179.google.com [209.85.213.179]) by dpdk.org (Postfix) with ESMTP id 023D58D3D for ; Tue, 27 Oct 2015 03:23:46 +0100 (CET) Received: by igpw7 with SMTP id w7so102213igp.1 for ; Mon, 26 Oct 2015 19:23:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber_org.20150623.gappssmtp.com; s=20150623; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=PHKZgCLL3rmFjb1nt71FS1/BTT5InrPeb4/w9ERB0mg=; b=ab4Qd4Zdt6QBwCKcB3kCDMk3Y4UY0qBzlEgNQTiGJkkOG+oUAJn//dYbsaMraaMpr7 u9+4rZ/N9dJnN+MOUEcOuziLBqzAQzRF4Q1hREqgSjPUXZXuT8C+PbJjxw75OB22rvMC ZjFrDqde/hEwSO2uwWxzvkzA2aaxlDwcKUdNdw/t3/eBFt/00LwOn/uLRqSyIPfNZS7T 0J0rJtSA543+S2GY1VsIE3Yaavnziq+qcjRSNOnmGwd43bPg8RK6LaupWcYTrOP3lvCH pd7ygSTCM7BveF71gXP1JINFOoXfEm2830MoySBLuig3kalT7TnpWaK9svfqo+ENY9fS sxBg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=PHKZgCLL3rmFjb1nt71FS1/BTT5InrPeb4/w9ERB0mg=; b=g+wusoWD91jt4VUYcg1kuMr+EBWDZgzksSWnOFizm/MypjGYj7Yv3keuDiB5Yb/4DZ z6xbXTrFmkWJ3TDGmwial3t9yKvKT4DFcAJuiSV4n6RvY6za245GI8q+9hIjkfutetGX BoCyGwfHwRyhcDcTOtmGlKq/kf9uEdYJ9wqoKzH6MF0h9lY0KVKUhTmLUaSWGERNsisC v56Atx4h/7tRXs1kSPGDJoS9DwCdX2/EJESB9xhwi0aDUmAI/izgbu/79rPwdNhvjk6/ JpTE+pPoUAUhu7qOm9TUccDOB8PMD3fb65og+ZQqzVdqEgq6NdmMguL3mESwe8GuM3YP ySaQ== X-Gm-Message-State: ALoCoQkAUcJwYty4xPfF2DvRpYVn4In3xxnwPAkzkSA7xjj8Mj80zGRuJzMxeCGwivFiq2qepYtN MIME-Version: 1.0 X-Received: by 10.50.83.104 with SMTP id p8mr22377741igy.13.1445912625419; Mon, 26 Oct 2015 19:23:45 -0700 (PDT) Received: by 10.64.123.164 with HTTP; Mon, 26 Oct 2015 19:23:45 -0700 (PDT) In-Reply-To: References: <1445231772-17467-1-git-send-email-stephen@networkplumber.org> <1536056.KWEakoJpBK@xps13> <20151022090459.68015713@xeon-e3> <20151027085212.24ce7e5e@samsung9> Date: Tue, 27 Oct 2015 11:23:45 +0900 Message-ID: From: Stephen Hemminger To: "Xie, Huawei" Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.15 Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] [PATCH v2 0/5] virtio: Tx performance improvements X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 27 Oct 2015 02:23:46 -0000 You need to use the extended mergeable rx buffer format. It is a virtio spec requirement, look at Linux virtio network driver or ask the virtio maintainers for Linux if you need more clarification. On Tue, Oct 27, 2015 at 10:56 AM, Xie, Huawei wrote: > On 10/27/2015 7:52 AM, Stephen Hemminger wrote: > > On Fri, 23 Oct 2015 09:00:38 +0000 > > "Xie, Huawei" wrote: > > > >>>> Why use merge-able rx header here in the tx region? > >>> If mergeable rx is negotiated then the header must be used for > >>> both Tx and Rx. I chose to allocate the largest possible header > >>> needed, rather than having to deal with variable size data structure. > >> Our original code is also using merge-able header for TX descriptor if > >> this negotiated. > >> I checked the virtio spec, all of the merge-able header is about > >> receiving buffers, which is expected. That is why i feel weird here. > >> Maybe not a big deal? > > Since num_buffers is only in merge-able header, the negotiation is > implied > > to be symmetric. > > > Can we come to the conclusion that in tx case, we use merge-able header > though number_buffers is not used at all? > > Reading 0.95 spec > > > > Under "Packet Transmission" > > 3. If the driver negotatied the VIRTIO_NET_F_MGR_RXBUF feature > > the num_buffers field is set to zero. > > > > > >