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To: William Lee Irwin III <wli@holomorphy.com>
Cc: Daniel Phillips <phillips@bonn-fries.net>,
        Oliver Xymoron <oxymoron@waste.org>,
        Linus Torvalds <torvalds@transmeta.com>,
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Subject: Re: Note describing poor dcache utilization under high memory pressure
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	<87lmehft5b.fsf@fadata.bg> <E16VU2h-00009Y-00@starship.berlin>
	<20020129012007.H899@holomorphy.com>
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From: Momchil Velikov <velco@fadata.bg>
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Date: 29 Jan 2002 12:18:42 +0200
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>>>>> "William" == William Lee Irwin <wli@holomorphy.com> writes:

William> On Tue, Jan 29, 2002 at 09:55:02AM +0100, Daniel Phillips wrote:
>> It's only touching the ptes on tables that are actually used, so if a parent
>> with a massive amount of mapped memory forks a child that only instantiates
>> a small portion of it (common situation) then the saving is pretty big.

William> Please correct my attempt at clarifying this:
William> The COW markings are done at the next higher level of hierarchy above
William> the pte's themselves, and so experience the radix tree branch factor
William> reduction in the amount of work done at fork-time in comparison to a
William> full pagetable copy on fork.

COW at pgd/pmd level is ia32-ism, unlike COW at pte level.

Regards,
-velco

PS. Well, the whole pgd/pmd/ptb stuff is ia32-ism, but that's another
story.

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