From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Chmielewski Subject: Re: strange guest slowness after some time Date: Wed, 08 Apr 2009 07:45:53 +0200 Message-ID: <49DC3A11.2010107@wpkg.org> References: <49B29705.6000904@wpkg.org> <49D30801.5020201@wpkg.org> <49DA1D75.6000604@wpkg.org> <200904081019.14768.rusty@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: "David S. Ahern" , Felix Leimbach , avi@redhat.com, kvm@vger.kernel.org, Anthony Liguori To: Rusty Russell Return-path: Received: from mx03.syneticon.net ([78.111.66.105]:43849 "EHLO mx03.syneticon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762196AbZDHFp6 (ORCPT ); Wed, 8 Apr 2009 01:45:58 -0400 In-Reply-To: <200904081019.14768.rusty@rustcorp.com.au> Sender: kvm-owner@vger.kernel.org List-ID: Rusty Russell schrieb: > On Tuesday 07 April 2009 00:49:17 Tomasz Chmielewski wrote: >> Tomasz Chmielewski schrieb: >> >>> As I mentioned, it was using virtio net. >>> >>> Guests running with e1000 (and virtio_blk) don't have this problem. >> Also, virtio_console seem to be affected by this "slowness" issue. > > I'm pretty sure this is different. Older virtio_console code ignored > interrupts and polled, and use a heuristic to back off on polling (this was > because we used the generic "hvc" infrastructure which hacked support). By "older" you mean guest drivers? I have 2.6.27.x on guests and see this issue. If you meant host, I use kvm-84. > You'll find a delay on the first keystroke after idle, but none on the > second. I'm not sure. Press "a" seven times fast, and 7 characters will be printed a second later. But: wait one second more, it will be unresponsive again. You won't see the characters "as you type". Also these symptoms are very similar to virtio_net issue: - it happens only on some guest (even if they have the same kernel and userspace) after a random period of time - it used to happen for me _always_ when network got slow with virtio_net driver - it doesn't go away with guest restart initiated from guest's system - it goes away with kvm process stop/start (i.e. new kvm process), but can appear later with no apparent cause -- Tomasz Chmielewski http://wpkg.org