From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: virtio net regression Date: Sun, 19 Apr 2009 14:48:11 +0300 Message-ID: <49EB0F7B.3040802@redhat.com> References: <49E63DB4.4090107@devloop.org.uk> <49E66FFB.4080504@nagafix.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Antoine Martin , "kvm@vger.kernel.org" , Rusty Russell To: Antoine Martin Return-path: Received: from mx2.redhat.com ([66.187.237.31]:57403 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757262AbZDSLsx (ORCPT ); Sun, 19 Apr 2009 07:48:53 -0400 In-Reply-To: <49E66FFB.4080504@nagafix.co.uk> Sender: kvm-owner@vger.kernel.org List-ID: Antoine Martin wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA512 > > Wireshark was showing a huge amount of invalid packets (wrong checksum) > - - that was the cause of the slowdown. > Simply rebooting the host into 2.6.28.9 fixed *everything*, regardless > of whether the guests use virtio or ne2k_pci/etc. > The guests are still running 2.6.29.1, but I am not likely to try that > release again on the host anytime soon! Ouch! > Strange, no significant tun changes between .28 and .29. Rusty, any idea? > Antoine > > Antoine Martin wrote: > >> Hi, >> >> I've got some hosts that were happily running the 2.6.25.x host kernel, >> kvm-84, kernel.org kvm modules. >> The guests were running 2.6.25 to 2.6.29.x quite happily. >> Network was using virtio. >> Since I upgraded one of the hosts (Intel dual core) to 2.6.29.x >> yesterday, the virtio network performance of the guests on it dropped >> dramatically. (for some reason another AMD host did not seem to be >> affected...) >> Here are the tests I performed using wget and scp: >> * guest to guest: fast >> * guest to host: fast >> * host to internet: fast >> * guest to internet: slow!!! >> I was normally getting ~5MB/s to the host (speed to the internet was >> limited by the capacity of the DSL line), but since the upgrade the >> performance had dropped to around 20KB/s! >> Strangely enough, I could open many new connections to the guest and get >> more chunks all at 20KB/s! >> I switched the guests to using ne2k_pci and the performance has been >> restored... >> >> And this is where it gets even weirder... >> UDP packets get corrupted using ne2k_pci and rtl8139cp but not with >> virtio... >> So I can get performance or UDP, but not both... >> >> Let me know if there is anything more I can provide to help fix this >> regression. >> I can reproduce the problem quite easily without causing problems on the >> host. >> >> Cheers >> Antoine >> -- >> 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 >> > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.9 (GNU/Linux) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org > > iEUEAREKAAYFAknmb/sACgkQGK2zHPGK1ruzgwCWPMvAJzToIMbrE7k2K2FHBQlk > dQCcCpDrTufqIN4ZSQs/dMLTQMYtTAU= > =lDW9 > -----END PGP SIGNATURE----- > -- > 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 > -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.