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SubjectRe: -mm merge plans -- anti-fragmentation
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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