From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH v2] vhost: Add indirect descriptors support to the TX path Date: Fri, 23 Sep 2016 11:24:16 -0700 Message-ID: <20160923112416.4f798b4b@xeon-e3> References: <1474615009-26626-1-git-send-email-maxime.coquelin@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: yuanhan.liu@linux.intel.com, huawei.xie@intel.com, dev@dpdk.org, vkaplans@redhat.com, mst@redhat.com To: Maxime Coquelin Return-path: Received: from mail-pf0-f177.google.com (mail-pf0-f177.google.com [209.85.192.177]) by dpdk.org (Postfix) with ESMTP id 57364231C for ; Fri, 23 Sep 2016 20:24:07 +0200 (CEST) Received: by mail-pf0-f177.google.com with SMTP id s13so10088799pfd.2 for ; Fri, 23 Sep 2016 11:24:07 -0700 (PDT) In-Reply-To: <1474615009-26626-1-git-send-email-maxime.coquelin@redhat.com> 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, 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?