From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by dpdk.org (Postfix) with ESMTP id 171B0475E for ; Mon, 10 Oct 2016 05:49:38 +0200 (CEST) Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga103.jf.intel.com with ESMTP; 09 Oct 2016 20:49:38 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.31,470,1473145200"; d="scan'208";a="1062633974" Received: from yliu-dev.sh.intel.com (HELO yliu-dev) ([10.239.67.162]) by orsmga002.jf.intel.com with ESMTP; 09 Oct 2016 20:49:36 -0700 Date: Mon, 10 Oct 2016 11:50:28 +0800 From: Yuanhan Liu To: Maxime Coquelin Cc: "Michael S. Tsirkin" , Stephen Hemminger , dev@dpdk.org, qemu-devel@nongnu.org Message-ID: <20161010035028.GX1597@yliu-dev.sh.intel.com> References: <1474872056-24665-1-git-send-email-yuanhan.liu@linux.intel.com> <1474872056-24665-2-git-send-email-yuanhan.liu@linux.intel.com> <20160926221112-mutt-send-email-mst@kernel.org> <20160927031158.GA25823@yliu-dev.sh.intel.com> <20160927224935-mutt-send-email-mst@kernel.org> <20160928022848.GE1597@yliu-dev.sh.intel.com> <20160929205047-mutt-send-email-mst@kernel.org> <2889e609-f750-a4e1-66f8-768bb07a2339@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2889e609-f750-a4e1-66f8-768bb07a2339@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Subject: Re: [dpdk-dev] [Qemu-devel] [PATCH 1/2] vhost: enable any layout feature 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, 10 Oct 2016 03:49:39 -0000 On Thu, Sep 29, 2016 at 10:05:22PM +0200, Maxime Coquelin wrote: > >so doing this unconditionally would be a spec violation, but if you see > >value in this, we can add a feature bit. > Right it would be a spec violation, so it should be done conditionally. > If a feature bit is to be added, what about VIRTIO_NET_F_NO_TX_HEADER? > It would imply VIRTIO_NET_F_CSUM not set, and no GSO features set. > If negotiated, we wouldn't need to prepend a header. If we could skip Tx header, I think we could also skip Rx header, in the case when mrg-rx is aslo turned off? > From the micro-benchmarks results, we can expect +10% compared to > indirect descriptors, and + 5% compared to using 2 descs in the > virtqueue. > Also, it should have the same benefits as indirect descriptors for 0% > pkt loss (as we can fill 2x more packets in the virtqueue). > > What do you think? I would vote for this. It should yield maximum performance for the case that it's guaranteed that packet size will always fit in a typical MTU (1500). --yliu