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 16:12:13 +0300 Message-ID: <4A379A2D.5000304@redhat.com> References: <4A36B025.2080602@us.ibm.com> <4A37618E.6040606@redhat.com> <4A379504.4080100@us.ibm.com> <4A3795F4.9080507@redhat.com> <4A3796B1.8060003@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]:40234 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753623AbZFPNME (ORCPT ); Tue, 16 Jun 2009 09:12:04 -0400 In-Reply-To: <4A3796B1.8060003@us.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06/16/2009 03:57 PM, Anthony Liguori wrote: >>> >>> 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). > > In order to complete the requests, you have to call a callback and > pass an opaque with the results. The callback/opaque cannot be saved > in the block layer in a meaningful way. > You're right, of course. I guess we'll have to cancel any near term cancellation plans. We could change the opaque to be something pre-registered (e.g. the device state object, which we don't need to save/restore) and pass in addition an integer request tag. These would be migratable. The device would be responsible for saving tags and their associated information (perhaps through a common API). -- error compiling committee.c: too many arguments to function