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SubjectRe: [PATCH] low order lumpy reclaim also should use PAGEOUT_IO_SYNC.
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> Hi, Kosaki-san. 
>
> On Tue, 21 Apr 2009 14:22:27 +0900 (JST)
> KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
>
> > Subject: [PATCH] low order lumpy reclaim also should use PAGEOUT_IO_SYNC.
> >
> > commit 33c120ed2843090e2bd316de1588b8bf8b96cbde (more aggressively use lumpy reclaim)
> > change lumpy reclaim using condition. but it isn't enough change.
> >
> > lumpy reclaim don't only mean isolate neighber page, but also do pageout as synchronous.
> > this patch does it.
>
> I agree.
>
> Andi added synchronous lumpy reclaim with c661b078fd62abe06fd11fab4ac5e4eeafe26b6d.
> At that time, lumpy reclaim is not agressive.
> His intension is just for high-order users.(above PAGE_ALLOC_COSTLY_ORDER).
>
> After some time, Rik added aggressive lumpy reclaim with 33c120ed2843090e2bd316de1588b8bf8b96cbde.
> His intension is that do lumpy reclaim when high-order users and trouble getting a small set of contiguous pages.
>
> So we also have to add synchronous pageout for small set of contiguous pages.
> Nice catch!.
>
> Reviewed-by: Minchan Kim <Minchan.kim@gmail.com>
>
> BTW, Do you have any number ?

No.

Actually, this logic only run when system is strongly memory stavation
or fragment. not normal case.

At that time, another slowdown thing hide synchronous reclaim latency, I think.





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