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Re: [Xen-devel] sparse M2P table

To: Jan Beulich <JBeulich@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] sparse M2P table
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 16 Sep 2009 11:39:00 +0100
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On 16/09/2009 11:04, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

> I'm in the process of putting together patches to eliminate undue overhead
> resulting from Xen's current assumption on a non-sparse machine address
> map. After removing large holes (symmetric across all nodes) from the
> machine address map and after also mapping the resulting (much smaller)
> frame table sparsely (to account for smaller holes distinct for one or more
> nodes), I intended to also map the P2M table sparsely.

The guest P2Ms? Why would you want to do that - so that you can add some
hierarchy (and therefore sparseness) to the pseuo-phys address space too?
Otherwise I don't see why you would ever have a sparse P2M, and therefore
why you would care about efficiently handling large holes in it.

 -- Keir



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