Messages in this thread | | | Date | Tue, 5 Aug 2008 17:28:00 +0100 | From | Mel Gorman <> | Subject | Re: [RFC] [PATCH 0/5 V2] Huge page backed user-space stacks |
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On (05/08/08 09:12), Dave Hansen didst pronounce: > On Tue, 2008-08-05 at 12:11 +0100, Mel Gorman wrote: > > See, that's great until you start dealing with MAP_SHARED|MAP_ANONYMOUS. > > To get that right between children, you end up something very fs-like > > when the child needs to fault in a page that is already populated by the > > parent. I strongly suspect we end up back at hugetlbfs backing it :/ > > Yeah, but the case I'm worried about is plain anonymous. We already > have the fs to back SHARED|ANONYMOUS, and they're not really > anonymous. :) > > This patch *really* needs anonymous pages, and it kinda shoehorns them > in with the filesystem. Stacks aren't shared at all, so this is a > perfect example of where we can forget the fs, right? >
Ok sure, you could do direct inserts for MAP_PRIVATE as conceptually it suits this patch. However, I don't see what you gain. By reusing hugetlbfs, we get things like proper reservations which we can do for MAP_PRIVATE these days. Again, we could call that sort of thing directly if the reservation layer was split out separate from hugetlbfs but I still don't see the gain for all that churn.
What am I missing?
-- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab
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