From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f54.google.com (mail-pa0-f54.google.com [209.85.220.54]) by dpdk.org (Postfix) with ESMTP id DCCF88D8A for ; Tue, 27 Oct 2015 00:52:20 +0100 (CET) Received: by pasz6 with SMTP id z6so202146701pas.2 for ; Mon, 26 Oct 2015 16:52:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber_org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-type:content-transfer-encoding; bh=KRGUySOJB2klCb52LD0QGNWTCGAqm5oOyOjFKZ9IcOk=; b=lJaNIYHZAaTT32WtsSBgizT/diNiphRJv1tXZ/lP0kf8Xj4Ft1fkUxUQsGVncdMMeh GMJFRDLuN3tTuqQ3Jv+CoeJnRwNJIWzKYYICt1O2LDSkhfDeOWMDen5YFhPFQfzwbNRp Rvl07uMSnnSXm6Q7OGNteyfY1/gWcmImhdoLtx1u2NssaKlZgyt34T7AFsW1aEWDAO7S L8p4nScpEAD98XuS292gmW86P2hJ6zmvHzdKuRPsxe+sXjUGvXjSywdyBuAzynwHDfXo bIrqWX9j6VIWVCeyGTRoowHcCpkwB/IKHkt3K107Yo/v02N2UyNrX1W5+Q8ZrBh8TaLR uwvA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:mime-version:content-type:content-transfer-encoding; bh=KRGUySOJB2klCb52LD0QGNWTCGAqm5oOyOjFKZ9IcOk=; b=Vc6eyThChQsBTO4EA6NVYE4ym3AKusgm9r0acl7tNpkAyZ+fFmcqMA1kO/eVOjNU8m LPmUE3JHvF6VnSX5lugwQm6tsiq42thFt4xlawkPxVGCjEUNamLjYm/Z0i7iEkFO5iYY MXKDJmAwS7igiMTEv00gUseEFRXLbR/C/tizQMS3uELJraQxNfxPukpu45ZCi1N11VK3 jGo8AoznpU+j/CglsxWoIXiQ01/LJRCZYeLMguV4RI5k2Vr4JLmivMuTRUAYYuf0CP1Z JcKKUmhJGZDynVZTMSWovmVLUeG+lDprxD06pnbeqbnAGmevxNKpWoNctc4V12uCbwUE uPbg== X-Gm-Message-State: ALoCoQl5Vbh/CqzuH9p+nNAI6fH1MuXVr5uAQWfDTocwYIeqxwcQSUuGe85r+0xk1Hzsl8meUXya X-Received: by 10.66.122.98 with SMTP id lr2mr43796582pab.146.1445903540266; Mon, 26 Oct 2015 16:52:20 -0700 (PDT) Received: from samsung9 ([144.49.132.22]) by smtp.gmail.com with ESMTPSA id u3sm35952103pbs.33.2015.10.26.16.52.18 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 26 Oct 2015 16:52:20 -0700 (PDT) Date: Tue, 27 Oct 2015 08:52:12 +0900 From: Stephen Hemminger To: "Xie, Huawei" Message-ID: <20151027085212.24ce7e5e@samsung9> In-Reply-To: References: <1445231772-17467-1-git-send-email-stephen@networkplumber.org> <1536056.KWEakoJpBK@xps13> <20151022090459.68015713@xeon-e3> X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.25; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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: Mon, 26 Oct 2015 23:52:21 -0000 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. 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.