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Re: [xen-devel][vNUMA v2][PATCH 2/8] public interface

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: Re: [xen-devel][vNUMA v2][PATCH 2/8] public interface
From: Andre Przywara <andre.przywara@xxxxxxx>
Date: Tue, 3 Aug 2010 23:35:02 +0200
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Dulloor <dulloor@xxxxxxxxx>
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Keir Fraser wrote:
On 03/08/2010 16:43, "Dulloor" <dulloor@xxxxxxxxx> wrote:

I would expect guest would see nodes 0 to nr_vnodes-1, and the mnode_id
could go away.
mnode_id maps the vnode to a particular physical node. This will be
used by balloon driver in
the VMs when the structure is passed as NUMA enlightenment to PVs and
PV on HVMs.
I have a patch ready for that (once we are done with this series).

So what happens when the guest is migrated to another system with different
physical node ids? Is that never to be supported? I'm not sure why you
wouldn't hide the vnode-to-mnode translation in the hypervisor.
And what about if the node assignment changes at guest's runtime to satisfy load-balancing? I think we should have the opportunity to change the assignment, although this could be costly when it involves copying guest memory to another physical location. A major virtualization product ;-) solves this by a "hot pages first, the rest in background" algorithm. I see that this is definitely a future extension, but we shouldn't block this way already in this early stage.


Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 448-3567-12

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