From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: Live migration broken when under heavy IO Date: Tue, 16 Jun 2009 07:57:21 -0500 Message-ID: <4A3796B1.8060003@us.ibm.com> References: <4A36B025.2080602@us.ibm.com> <4A37618E.6040606@redhat.com> <4A379504.4080100@us.ibm.com> <4A3795F4.9080507@redhat.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: Avi Kivity Return-path: Received: from e7.ny.us.ibm.com ([32.97.182.137]:55807 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758610AbZFPM5X (ORCPT ); Tue, 16 Jun 2009 08:57:23 -0400 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by e7.ny.us.ibm.com (8.13.1/8.13.1) with ESMTP id n5GCj8b9014065 for ; Tue, 16 Jun 2009 08:45:08 -0400 Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v9.2) with ESMTP id n5GCvN9K247974 for ; Tue, 16 Jun 2009 08:57:23 -0400 Received: from d01av03.pok.ibm.com (loopback [127.0.0.1]) by d01av03.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n5GCvNUW025565 for ; Tue, 16 Jun 2009 08:57:23 -0400 In-Reply-To: <4A3795F4.9080507@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > Yes, that's even better (though without linux-aio, it's equivalent). Not absolutely equivalent. There many be queued requests that haven't yet been dispatched to the thread pool, but yeah, I understand what you mean. >> >> 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. -- Regards, Anthony Liguori