From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v2] vhost: Add indirect descriptors support to the TX path Date: Fri, 23 Sep 2016 21:31:27 +0300 Message-ID: <20160923213055-mutt-send-email-mst@kernel.org> References: <1474615009-26626-1-git-send-email-maxime.coquelin@redhat.com> <20160923112416.4f798b4b@xeon-e3> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Maxime Coquelin , yuanhan.liu@linux.intel.com, huawei.xie@intel.com, dev@dpdk.org, vkaplans@redhat.com To: Stephen Hemminger Return-path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 862FA6CA4 for ; Fri, 23 Sep 2016 20:31:29 +0200 (CEST) Content-Disposition: inline In-Reply-To: <20160923112416.4f798b4b@xeon-e3> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Fri, Sep 23, 2016 at 11:24:16AM -0700, Stephen Hemminger wrote: > On Fri, 23 Sep 2016 09:16:49 +0200 > Maxime Coquelin wrote: > > > Indirect descriptors are usually supported by virtio-net devices, > > allowing to dispatch a larger number of requests. > > > > When the virtio device sends a packet using indirect descriptors, > > only one slot is used in the ring, even for large packets. > > > > The main effect is to improve the 0% packet loss benchmark. > > A PVP benchmark using Moongen (64 bytes) on the TE, and testpmd > > (fwd io for host, macswap for VM) on DUT shows a +50% gain for > > zero loss. > > > > On the downside, micro-benchmark using testpmd txonly in VM and > > rxonly on host shows a loss between 1 and 4%.i But depending on > > the needs, feature can be disabled at VM boot time by passing > > indirect_desc=off argument to vhost-user device in Qemu. > > > > Signed-off-by: Maxime Coquelin > > What about supporting VIRTIO_F_ANY_LAYOUT? I thought it's already supported. That's required by virtio 1 and dpdk claims support for that. -- MST