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Re: [Xen-devel] Xen 3.4.1 NUMA support

To: Jan Beulich <JBeulich@xxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Xen 3.4.1 NUMA support
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 10 Nov 2009 08:57:49 +0000
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Andre Przywara <andre.przywara@xxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Papagiannis Anastasios <apapag@xxxxxxxxxxxx>
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On 10/11/2009 08:51, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>> What default confinement? I thought guests had an all-pCPUs affinity mask be
>> default?
> Not with numa=on (see also Andre's post to this effect): The guest will
> get assigned to a node, and its affinity set to that node's CPUs.

...And if it didn't, striping would not happen. In fact iirc the default
NUMA allocation policy for an all-pcpus domain is in some respects pessimal:
vcpu0's initial node gets drained of memory first. I.e., you get *less*
'striping' than you could with numa=off where you might at least get lucky.

 -- Keir

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