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Re: [Xen-devel] Xen CPU limit?

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] Xen CPU limit?
From: Pasi Kärkkäinen <pasik@xxxxxx>
Date: Tue, 30 Mar 2010 10:53:06 +0300
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Martin Lukasik <martin.lukasik@xxxxxxxxxxxxx>
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On Tue, Mar 30, 2010 at 08:16:26AM +0100, Jan Beulich wrote:
> >>> Pasi Kärkkäinen<pasik@xxxxxx> 29.03.10 17:49 >>>
> >I think the number of virtual cpus (vcpus) per guest is (was) 32,
> >and now in Xen 4.0.0 you can have up to 64 vcpus per guest.
> I don't think the tools are up to anything beyond 32 yet. 

Hmm.. what's actually missing from the tools to handle >32 vcpus?

> The (64-bit) hypervisor allows up to 8192 vCPU-s iirc (but that's a truly
> theoretical limit, as Dom0 or a guest likely won't be able to bring up
> that many due to there only being 4096 event channels; current
> Linux requires 5-6 of them per vCPU for IPIs and timer vIRQ).

Wow.. I wasn't aware the (theoretical) limit is that big :)

-- Pasi

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