From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark McLoughlin Subject: Re: [PATCH 0/9][RFC] KVM virtio_net performance Date: Fri, 25 Jul 2008 18:17:14 +0100 Message-ID: <1217006234.7098.88.camel@muff> References: <1216899979-32532-1-git-send-email-markmc@redhat.com> <4888EC61.8050208@codemonkey.ws> Reply-To: Mark McLoughlin Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Herbert Xu , Rusty Russell To: Anthony Liguori Return-path: Received: from mx1.redhat.com ([66.187.233.31]:46363 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751136AbYGYRRj (ORCPT ); Fri, 25 Jul 2008 13:17:39 -0400 In-Reply-To: <4888EC61.8050208@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: On Thu, 2008-07-24 at 15:56 -0500, Anthony Liguori wrote: > Hi Mark, > > Mark McLoughlin wrote: > > Hey, > > Here's a bunch of patches attempting to improve the performance > > of virtio_net. This is more an RFC rather than a patch submission > > since, as can be seen below, not all patches actually improve the > > perfomance measurably. > > > > I'm still seeing the same problem I saw with my patch series. Namely, > dhclient fails to get a DHCP address. Rusty noticed that RX has a lot > more packets received then it should so we're suspicious that we're > getting packet corruption. I've just tried bridging to my physical LAN and DHCP seems to be working fine. Which reminds me, though - doing this makes host->guest throughput drop to well below pre-GSO figures. GSO appears to be disabled while there's a physical interface on the bridge. If I remove eth0, the figures jump right back up again. I also just noticed that the GSO patch breaks e1000 because it unconditionally sets IFF_VNET_HDR. Will fix that up. > Configuring the tap device with a static address, here's what I get with > iperf: > > w/o patches: > > guest->host: 625 Mbits/sec > host->guest: 825 Mbits/sec > > w/patches > > guest->host: 2.02 Gbits/sec > host->guest: 1.89 Gbits/sec > > guest lo: 4.35 Gbits/sec > host lo: 4.36 Gbits/sec I tried iperf at one point and was getting really low figures; not sure why. Apart from your iperf figures being lower than my netperf figures, it also contradicts what I was seeing - namely guest->host beating host->guest before the patches and host->guest beating guest->host after the patches. It could all just be down to the length of the tx timer. If you try adjusting that does it help? > This is with KVM GUEST configured FWIW. Yep, same here. Cheers, Mark.