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Re: [Qemu-devel] [PATCH 1/2] sched: add virt sched domain for the guest

From: Dave Hansen
Subject: Re: [Qemu-devel] [PATCH 1/2] sched: add virt sched domain for the guest
Date: Wed, 23 May 2012 08:23:06 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1

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. ;)

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