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Re: [PATCH] 64K page size

To: Ralf Baechle <>
Subject: Re: [PATCH] 64K page size
From: Peter Watkins <>
Date: Thu, 31 Aug 2006 11:12:02 -0400
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Ralf Baechle wrote:

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.

Yes, in some cases. I'd like to benchmark the performance difference between 2 and 3 level pagetables, so the choice is valuable.

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