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Date: Wed, 19 May 2004 00:44:24 -0700
From: Andrew Morton <akpm@osdl.org>
To: Albert Cahalan <albert@users.sourceforge.net>
Cc: linux-kernel@vger.kernel.org, riel@redhat.com
Subject: Re: pte_addr_t size reduction for 64 GB case?
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Albert Cahalan <albert@users.sourceforge.net> wrote:
>
> When handling 64 GB on i386, pte_addr_t really only
> needs 33 bits to find the PTE. It sure doesn't need
> the full 64 bits it is using.

yup.

> How about cheating a bit? If the pte_addr_t only had
> the high 32 bits of the 36-bit pointer, it would point
> to a pair of the 8-byte PTEs in a 16-byte chunk of RAM.
> Then simply examine the PTEs to see which one is the
> correct one.

They might both map the same page.  It could overflow into page->flags.