From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Hetze Subject: Re: Virtio network performance poorer than emulated e1000 Date: Fri, 23 Jul 2010 15:37:31 +0200 Message-ID: <20100723133731.53EECB0016@mail.linux-ag.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org To: Balachandar Return-path: Received: from ironport.linux-ag.com ([62.245.157.240]:64457 "EHLO ironport.linux-ag.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753907Ab0GWNrj (ORCPT ); Fri, 23 Jul 2010 09:47:39 -0400 Received: from localhost (mail.linux-ag.de [62.245.157.206]) by mail.linux-ag.de (Postfix) with ESMTP id 53EECB0016 for ; Fri, 23 Jul 2010 15:37:31 +0200 (CEST) Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: I did some benchmarking mainly with tbench and found virtio better with big packages/maximum throughput and e1000 better with small packages/latency. vhost-net improves virtio quite a lot and makes it superior to the emulated devices. If network performance is a real issue, DMAR/IOMMU gives you direct access to dedicated network devices with nearly 100% native throughput and latency. Best regards, Sebastian On Thu, Jul 22, 2010 at 04:13:29PM -0400, Balachandar wrote: > I can see that virtio network performance is poorer than emaulated > e1000 nic. I did some simple ping test and with emulated e1000 the > average rtt is around 600 microsec. With virtio the average rtt is 800 > microsec. I am using a tap + bridge configuration. I run kvm as > follows > > kvm -m 512 -hda vdisk.img \ > -net nic,model=virtio \ > -net tap,ifname=tap0,script=qemu-ifup,downscript=no > > I am running Debian squeeze distribution with guest and host kernel 2.6.34. > > Does anyone else see some results like this or is it only me? Could > changing the distribution help as i am running a testing one? > > Thanks, > Bala