[PATCH -V7 01/18] mm/THP: HPAGE_SHIFT is not a #define on some arch

[David Gibson]

On Mon, Apr 29, 2013 at 01:07:22AM +0530, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar at linux.vnet.ibm.com>
> 
> On archs like powerpc that support different hugepage sizes, HPAGE_SHIFT
> and other derived values like HPAGE_PMD_ORDER are not constants. So move
> that to hugepage_init

These seems to miss the point.  Those variables may be defined in
terms of HPAGE_SHIFT right now, but that is of itself kind of broken.
The transparent hugepage mechanism only works if the hugepage size is
equal to the PMD size - and PMD_SHIFT remains a compile time constant.

There's no reason having transparent hugepage should force the PMD
size of hugepage to be the default for other purposes - it should be
possible to do THP as long as PMD-sized is a possible hugepage size.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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