From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark McLoughlin Subject: Re: massive performance drop after a while when using virtio nics Date: Tue, 09 Sep 2008 11:47:15 +0100 Message-ID: <1220957235.12615.47.camel@muff> References: <1219519317.2909.12.camel@decade.local> <1220955720.12615.28.camel@muff> <1220956332.3011.4.camel@decade.local> Reply-To: Mark McLoughlin Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Fabian Deutsch Return-path: Received: from mx2.redhat.com ([66.187.237.31]:54442 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750754AbYIIKsx (ORCPT ); Tue, 9 Sep 2008 06:48:53 -0400 In-Reply-To: <1220956332.3011.4.camel@decade.local> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, 2008-09-09 at 12:32 +0200, Fabian Deutsch wrote: > Am Dienstag, den 09.09.2008, 11:22 +0100 schrieb Mark McLoughlin: > > Hi, > > > > On Sat, 2008-08-23 at 21:21 +0200, Fabian Deutsch wrote: > > > Hey. > > > > > > When running a guest in the following setup, I observ a "massive" > > > performance decrease after a couple of gigabytes of transfrerred data. > > > > > > other guests keep running fine (no regressions) and nothing unusual is > > > observed on the host. > > > > If you do "killall -ALRM qemu-kvm" after the slowdown has occurred, does > > it make things speed up again for a while? > > > > It seems so! > Fantastic. > > > If so, the issue is fixed by: > > > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=ba661292a2bc6ddd305a212b0526e5dc22195fe7 > > > > It also got applied in 2.6.26.3 and 2.6.25.16. > > > > So it was some signaling-bug on the .. client side? No, it was a kernel race condition causing the qemu-kvm process to stop receiving SIGALRM signals. The original thread might explain it a bit better: http://thread.gmane.org/gmane.comp.emulators.kvm.devel/19582 Cheers, Mark.