Re: [PATCH] MM: Support more pagesizes for MAP_HUGETLB/SHM_HUGETLBv2

From: Rik van Riel
Date: Wed Jun 13 2012 - 16:39:01 EST


On 06/13/2012 04:31 PM, Andi Kleen wrote:
On Wed, Jun 13, 2012 at 04:24:47PM -0400, Rik van Riel wrote:
This would also be useful for emulators such as qemu-kvm,
which want the guest memory to be 2MB aligned.

hugetlbfs does implicit align, so right now I mash
the two together and use up many of the remaining bits

If you want align different than page sizes you may need
to go 64bits with the flags.

All alignment is a power of two, so six bits should
be enough for up to 2^64 pages :)

Is there a use case for alignment independent of page sizes?

No, but page size differs per architecture and it
would be nice if we could share arch_get_unmapped_area
and related code in mm/, instead of every architecture
having its own.

In fact, that is what I am working on right now, and
my current road block is the page colouring code :)
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