From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:36718) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SXDZt-0001oj-TX for qemu-devel@nongnu.org; Wed, 23 May 2012 11:34:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SXDZl-0002iE-BL for qemu-devel@nongnu.org; Wed, 23 May 2012 11:34:21 -0400 Received: from e7.ny.us.ibm.com ([32.97.182.137]:56551) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SXDZl-0002gH-7R for qemu-devel@nongnu.org; Wed, 23 May 2012 11:34:13 -0400 Received: from /spool/local by e7.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 23 May 2012 11:34:07 -0400 Received: from d01relay01.pok.ibm.com (d01relay01.pok.ibm.com [9.56.227.233]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id 923E66E8536 for ; Wed, 23 May 2012 11:23:49 -0400 (EDT) Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by d01relay01.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q4NFNiEq058938 for ; Wed, 23 May 2012 11:23:45 -0400 Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q4NKsTZ9003367 for ; Wed, 23 May 2012 16:54:30 -0400 Message-ID: <4FBD00DA.5080308@linux.vnet.ibm.com> Date: Wed, 23 May 2012 08:23:06 -0700 From: Dave Hansen MIME-Version: 1.0 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 Subject: Re: [Qemu-devel] [PATCH 1/2] sched: add virt sched domain for the guest List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Zijlstra Cc: kvm@vger.kernel.org, qemu-devel@nongnu.org, Liu ping fan , linux-kernel@vger.kernel.org, Ingo Molnar , Avi Kivity , Anthony Liguori 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. ;)