From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 629554A59 for ; Sun, 25 Sep 2016 03:02:31 +0200 (CEST) Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8DB196540B; Sun, 25 Sep 2016 01:02:30 +0000 (UTC) Received: from redhat.com (vpn-61-253.rdu2.redhat.com [10.10.61.253]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with SMTP id u8P12Tkj025526; Sat, 24 Sep 2016 21:02:29 -0400 Date: Sun, 25 Sep 2016 04:02:28 +0300 From: "Michael S. Tsirkin" To: Stephen Hemminger Cc: Maxime Coquelin , yuanhan.liu@linux.intel.com, huawei.xie@intel.com, dev@dpdk.org, vkaplans@redhat.com Message-ID: <20160925035832-mutt-send-email-mst@kernel.org> References: <1474615009-26626-1-git-send-email-maxime.coquelin@redhat.com> <20160923112416.4f798b4b@xeon-e3> <20160923213055-mutt-send-email-mst@kernel.org> <20160923132805.3207f1fa@xeon-e3> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160923132805.3207f1fa@xeon-e3> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Sun, 25 Sep 2016 01:02:30 +0000 (UTC) Subject: Re: [dpdk-dev] [PATCH v2] vhost: Add indirect descriptors support to the TX path 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: Sun, 25 Sep 2016 01:02:31 -0000 On Fri, Sep 23, 2016 at 01:28:05PM -0700, Stephen Hemminger wrote: > On Fri, 23 Sep 2016 21:31:27 +0300 > "Michael S. Tsirkin" wrote: > > > 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. > > > > I don't see the flag set in the DPDK vhost driver feature bits > (at least in the source). > > /* Features supported by this lib. */ > #define VHOST_SUPPORTED_FEATURES ((1ULL << VIRTIO_NET_F_MRG_RXBUF) | \ > (1ULL << VIRTIO_NET_F_CTRL_VQ) | \ > (1ULL << VIRTIO_NET_F_CTRL_RX) | \ > (1ULL << VIRTIO_NET_F_GUEST_ANNOUNCE) | \ > (VHOST_SUPPORTS_MQ) | \ > (1ULL << VIRTIO_F_VERSION_1) | \ > (1ULL << VHOST_F_LOG_ALL) | \ > (1ULL << VHOST_USER_F_PROTOCOL_FEATURES) | \ > (1ULL << VIRTIO_NET_F_HOST_TSO4) | \ > (1ULL << VIRTIO_NET_F_HOST_TSO6) | \ > (1ULL << VIRTIO_NET_F_CSUM) | \ > (1ULL << VIRTIO_NET_F_GUEST_CSUM) | \ > (1ULL << VIRTIO_NET_F_GUEST_TSO4) | \ > (1ULL << VIRTIO_NET_F_GUEST_TSO6)) I see. It's implied by VERSION_1 in fact. In other words if VERSION_1 is negotiated then bit 27 isn't ANY_LAYOUT, it's in fact reserved. -- MST