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SubjectRe: [VM PATCH 2.6.8-rc1] Prevent excessive scanning of lower zone
Hi Andrew,

--- Andrew Morton <akpm@osdl.org> wrote:

> Shantanu Goel <sgoel01@yahoo.com> wrote:
> >
> > I emailed this a few weeks back to the list but it
> > seems to have gotten lost...
>
> It came through. I was unable to reproduce the
> disproportional scanning
> rate on almost exactly the same setup, so I parked
> the problem for a while.
>
> I do agree with the analysis though. The problem
> _could_ occur. I dunno
> why it happens for you and not for me...
>

Actually, the analysis turned out to be not entirely
correct. I think I have identified the offending
code. Please see attached patch. It makes kswapd()
skip zones which contain greater than "pages_high"
pages.

Machine setup is the same as before.
2x2.0Ghz Xeon w/HT, memory 256M (manually pegged).
I see this lopsided lower zone scanning on a dual
Opteron machine as well.

Attached are the kernbench results for stock 2.6.8-rc1
and 2.6.8-rc1 with patch.

Thanks,
Shantanu



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