Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964837Ab2EWP4U (ORCPT ); Wed, 23 May 2012 11:56:20 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:38100 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758484Ab2EWP4S (ORCPT ); Wed, 23 May 2012 11:56:18 -0400 Message-ID: <4FBD00DA.5080308@linux.vnet.ibm.com> Date: Wed, 23 May 2012 08:23:06 -0700 From: Dave Hansen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: Peter Zijlstra CC: Liu ping fan , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, Ingo Molnar , Avi Kivity , Anthony Liguori Subject: Re: [PATCH 1/2] sched: add virt sched domain for the guest References: <1337754751-9018-1-git-send-email-kernelfans@gmail.com> <1337754751-9018-2-git-send-email-kernelfans@gmail.com> <1337759644.9698.49.camel@twins> <1337761402.9698.62.camel@twins> <1337762914.9698.65.camel@twins> In-Reply-To: <1337762914.9698.65.camel@twins> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12052315-4242-0000-0000-000001C19A35 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 968 Lines: 21 On 05/23/2012 01:48 AM, Peter Zijlstra wrote: > On Wed, 2012-05-23 at 16:34 +0800, Liu ping fan wrote: >> > so we need to migrate some of vcpus from node-B to node-A, or to >> > node-C. > This is absolutely broken, you cannot do that. > > A guest task might want to be node affine, it looks at the topology sets > a cpu affinity mask and expects to stay on that node. > > But then you come along, and flip one of those cpus to another node. The > guest task will now run on another node and get remote memory accesses. Insane, sure. But, if the node has physically gone away, what do we do? I think we've got to either kill the guest, or let it run somewhere suboptimal. Sounds like you're advocating killing it. ;) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/