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Date:	Thu, 31 Aug 2006 11:12:02 -0400
From:	Peter Watkins <treestem@gmail.com>
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To:	Ralf Baechle <ralf@linux-mips.org>
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Subject: Re: [PATCH] 64K page size
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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.