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RE: [Xen-ia64-devel] Virtual mem map

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "Tristan Gingold" <Tristan.Gingold@xxxxxxxx>, <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-ia64-devel] Virtual mem map
From: "Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>
Date: Wed, 11 Jan 2006 13:55:22 -0800
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Thread-topic: [Xen-ia64-devel] Virtual mem map
> When we're working around one specific issue, I hope the 
> solution can be more generic to cover future similar requirement.

Sorry for the delayed response... I'm still catching up
on my email backlog.

An important question to consider if we are looking for a more
generic solution is whether we should go to a 4K pagesize.
Currently, Xen/ia64 cannot support a guest that uses 4K pages.

I see common/page_alloc.c code may need to be reworked to handle
non-contiguous physical memory.  It appears there are a number
of pieces of code that assume pg+i always points to a valid
page as long as i < nr_pages.  We may be able to get around
that by extending the concept of zones but that will require
some rework in page_alloc.c too.

I can't resist pointing out that it might have been a good
idea to retain the flexibility that was in the original Xen/ia64
allocator, rather than move to the oversimplified Xen/x86 approach.
(There may be a lesson here that could be applied for the p2m issue?)
I know Kevin remembers this discussion, but for those of you
who might want to read some ancient history on this topic, see
the thread "[Xen-devel] A tale of three memory allocators" at:


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