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RE: [Xen-devel] [PATCH] permute with 2MB chunk

To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxxx>, "Cui, Dexuan" <dexuan.cui@xxxxxxxxx>, "Jean Guyader (Intern)" <Jean.Guyader@xxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] permute with 2MB chunk
From: "Ian Pratt" <Ian.Pratt@xxxxxxxxxxxxx>
Date: Thu, 20 Mar 2008 09:05:18 -0000
Cc: Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>
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Thread-topic: [Xen-devel] [PATCH] permute with 2MB chunk
> We also tested building an HVM guest with the permuted ordering of
> pages, versus reverse ordering, versus normal ordering. Only the
permuted
> ordering showed the problem. We assume that the permute() function has
an
> unfortunate interaction with the memory allocator in certain HVM guest
OSes,
> causing poor cache utilisation.

It's still very odd that the permutation fn only seems to effect Linux
running as a HVM guest and not as a PV guest. I still think there's
something we're not quite understanding.

Jean: have you definitely verified that building a domain with the
permute function does not affect Linux PV guests?

Thanks,
Ian


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