Re: Note describing poor dcache utilization under high memory pressure

[Momchil Velikov]

>>>>> "William" == William Lee Irwin <[e-mail]> 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.