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    SubjectRe: -mm merge plans -- anti-fragmentation
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    On (10/07/07 13:04), Peter Zijlstra didst pronounce:
    > On Tue, 2007-07-10 at 11:20 +0100, Mel Gorman wrote:
    >
    > <snip>
    >
    > > > lumpy-reclaim-v4.patch
    > >
    > > This patch is really what lumpy reclaim is. I believe Peter has looked
    > > at this and was happy enough at the time although he is cc'd here again
    > > in case this has changed. This is mainly useful with either grouping
    > > pages by mobility or the ZONE_MOVABLE stuff. However, at the time the
    > > patch was proposed, there was a feeling that it might help jumbo frame
    > > allocation on e1000's and maybe if fsblock optimistically uses
    > > contiguous pages it would have an application. I would like to see it go
    > > through to see does it help e1000 at least.
    >
    > I'm not seeing how this will help e1000 (and other jumbo drivers). They
    > typically allocate using GFP_ATOMIC, so in order to satisfy those you'd
    > need to either have a higher order watermark or do atomic defrag of the
    > free space.
    >

    It does help somewhat indirectly and in an unsatisfactory manner. When the
    higher watermarks are breached, the atomic allocation will still succeeed
    but kswapd will be poked to reclaim at a given order. This is similar to
    the problems SLUB hits when it uses high-orders frequently.

    --
    Mel Gorman
    Part-time Phd Student Linux Technology Center
    University of Limerick IBM Dublin Software Lab
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