From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Chmielewski Subject: Re: strange guest slowness after some time Date: Thu, 28 May 2009 16:58:58 +0200 Message-ID: <4A1EA6B2.4020002@wpkg.org> References: <49B29705.6000904@wpkg.org> <49D30801.5020201@wpkg.org> <49DA1D75.6000604@wpkg.org> <200904081019.14768.rusty@rustcorp.com.au> <4A1BD765.4080405@wpkg.org> <4A1BD8A7.9090404@redhat.com> <4A1BDB10.2030603@wpkg.org> <4A1BDC1F.5050708@redhat.com> <4A1BF7B0.70107@wpkg.org> <4A1BFE4B.7040300@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Rusty Russell , "David S. Ahern" , Felix Leimbach , kvm@vger.kernel.org, Anthony Liguori To: Avi Kivity Return-path: Received: from mx03.syneticon.net ([78.111.66.105]:49778 "EHLO mx03.syneticon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754809AbZE1O6k (ORCPT ); Thu, 28 May 2009 10:58:40 -0400 In-Reply-To: <4A1BFE4B.7040300@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > Tomasz Chmielewski wrote: >>> Maybe virtio is racy and a loaded host exposes the race. >> >> I see it happening with virtio on 2.6.29.x guests as well. >> >> So, what would you do if you saw it on your systems as well? ;) >> >> Add some debug routines into virtio_* modules? >> > > I'm no virtio expert. Maybe I'd insert tracepoints to record interrupts > and kicks. Accidentally, I made some "interesting" discovery. This ~2 MB video shows a kvm-86 guest being rebooted and GRUB started: http://syneticon.net/kvm/kvm-slowness.ogg GRUB has its timeout set to 50 seconds, and is supposed to show it on the screen by decreasing the number of seconds shown, every second. Here, GRUB decreases the second counter very fast by 2 seconds, then waits 2 seconds, then again decreases the number of sends by 2 seconds very fast, and so on. Perhaps my wording does not describe it very well though, so just try to download the video and open it i.e. in mplayer. Comments? -- Tomasz Chmielewski http://wpkg.org