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Re: [PATCH] 64K page size

To: Peter Watkins <treestem@gmail.com>
Subject: Re: [PATCH] 64K page size
From: Ralf Baechle <ralf@linux-mips.org>
Date: Tue, 29 Aug 2006 14:50:55 +0100
Cc: linux-mips@linux-mips.org
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On Wed, Aug 23, 2006 at 11:15:49AM -0400, Peter Watkins wrote:

> There are a number of changes required to support larger page sizes, but 
> this one I thought worth sending up right away.
> 
> The code in pgtable-64.h assumes TASK_SIZE is always bigger than a first 
> level PGDIR_SIZE. This is not the case for 64K pages, where task size is 
> 40 bits (1TB) and a pgd entry can map 42 bits. This leads to 
> USER_PTRS_PER_PGD being zero for 64K pages.

Do you actually need large address space?  The kernel could allow 2, 3 and
4-level pagetables easily but doesn't give that choice currently.

  Ralf

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