From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dor Laor Subject: Re: [PATCH 0/9][RFC] KVM virtio_net performance Date: Sat, 26 Jul 2008 00:29:52 +0300 Message-ID: <488A45D0.2030808@qumranet.com> References: <1216899979-32532-1-git-send-email-markmc@redhat.com> <4888EC61.8050208@codemonkey.ws> <1217006234.7098.88.camel@muff> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Anthony Liguori , kvm@vger.kernel.org, Herbert Xu , Rusty Russell To: Mark McLoughlin Return-path: Received: from il.qumranet.com ([212.179.150.194]:29939 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750832AbYGYVba (ORCPT ); Fri, 25 Jul 2008 17:31:30 -0400 In-Reply-To: <1217006234.7098.88.camel@muff> Sender: kvm-owner@vger.kernel.org List-ID: Mark McLoughlin wrote: > 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. > > Older iperf (~2.0.2) has locking vs yield bug and consumes lots of cpu. In 2.0.4 it is fixed. Can that be the difference? > 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. > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >