From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Live migration broken when under heavy IO Date: Tue, 16 Jun 2009 15:54:12 +0300 Message-ID: <4A3795F4.9080507@redhat.com> References: <4A36B025.2080602@us.ibm.com> <4A37618E.6040606@redhat.com> <4A379504.4080100@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "qemu-devel@nongnu.org" , kvm-devel To: Anthony Liguori Return-path: Received: from mx2.redhat.com ([66.187.237.31]:55242 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752593AbZFPMyB (ORCPT ); Tue, 16 Jun 2009 08:54:01 -0400 In-Reply-To: <4A379504.4080100@us.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06/16/2009 03:50 PM, Anthony Liguori wrote: > Avi Kivity wrote: >>> Does anyone have a clever idea how to fix this without just waiting >>> for all IO requests to complete? >> >> What's wrong with waiting for requests to complete? It should take a >> few tens of milliseconds. > > An alternative would be to attempt to cancel the requests. This > incurs no non-deterministic latency. Yes, that's even better (though without linux-aio, it's equivalent). > > The tricky bit is that this has to happen at the device layer because > the opaques cannot be saved in a meaningful way. > Do you mean the device has to record all cancelled requests and replay them? I think we can do it at the block layer (though we have to avoid it for nested requests). -- error compiling committee.c: too many arguments to function