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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support
Date: Fri, 12 Mar 2010 16:04:03 +0000
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To: Andrea Arcangeli <aarcange@redhat.com>
Cc: qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>

> > > $ cat /sys/kernel/mm/transparent_hugepage/hpage_pmd_size
> > > 2097152
> >
> > Is "pmd" x86 specific?
> 
> It's linux specific, this is common code, nothing x86 specific. In
> fact on x86 it's not called pmd but Page Directory. I've actually no
> idea what pmd stands for but it's definitely not x86 specific and it's
> just about the linux common code common to all archs. The reason this
> is called hpage_pmd_size is because it's a #define HPAGE_PMD_SIZE in
> the kernel code. So this entirely match the kernel internals
> _common_code_.

Hmm, ok. I'm guessing linux doesn't support anything other than "huge" and 
"normal" page sizes now, so it's a question of whether we want it to expose 
current implementation details, or say "Align big in-memory things this much 
for optimal TLB behavior".

Paul