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Re: [Xen-devel] Design question for PV superpage support

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Subject: Re: [Xen-devel] Design question for PV superpage support
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Tue, 03 Mar 2009 09:28:39 -0800
Cc: Dave McCracken <dcm@xxxxxxxx>, Mick.Jordan@xxxxxxx, Xen Developers List <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Dan Magenheimer wrote:
BTW, thinking ahead to ballooning with 2MB pages, are we prepared
to assume that a relinquished 2MB page can't be fragmented?
While this may be appealing for systems where nearly all
guests are using 2MB pages, systems where the 2MB guest is
an odd duck might suffer substantially by making that
assumption.

Well, I still think that 4k pages are a ludicrously tiny unit of memory for Xen to be dealing with, and it shouldn't bother to get out of bed for less than 2M. If we treat 4k pages as the special case then keeping the Xen heap unfragmented at the 2M level should be fairly easy, no?

   J

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