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Date: Thu, 16 Nov 2000 10:07:11 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: Andrea Arcangeli <andrea@suse.de>
cc: schwidefsky@de.ibm.com, mingo@chiara.elte.hu, linux-kernel@vger.kernel.org
Subject: Re: Memory management bug
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On Thu, 16 Nov 2000, Andrea Arcangeli wrote:
> 
> If they absolutely needs 4 pages for pmd pagetables due hardware constraints
> I'd recommend to use _four_ hardware pages for each softpage, not two.

Yes.

However, it definitely is an issue of making trade-offs. Most 64-bit MMU
models tend to have some flexibility in how you set up the page tables,
and it may be possible to just move bits around too (ie making both the
pmd and the pgd twice as large, and getting the expansion of 4 by doing
two expand-by-two's, for example, if the hardware has support for doing
things like that).

		Linus

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