Re: VM: 2.4.10 vs. 2.4.10-ac2 and qsort()

From: Rik van Riel (riel@conectiva.com.br)
Date: Mon Oct 01 2001 - 14:44:52 EST


On Mon, 1 Oct 2001, Alan Cox wrote:

> > I'm not sure either, since qsort doesn't really have much
> > locality of reference but just walks all over the place.
>
> qsort can be made to perform reasonably well providing you try to cache
> colour the objects you sort and try to use prefetches a bit.

That won't quite work when the qsort in question is 150%
the size of your RAM ;)

> > One thing which could make 2.4.10 faster for this single case
> > is the fact that it doesn't keep any page aging info, so IO
> > clustering won't be confused by the process accessing its
> > pages ;)
>
> I don't think that is too unusual a case. If the smarter vm is making
> poorer I/O clustering decisions it wants investigating

Absolutely, this is something we really want to know ...

I guess I'll play with Lorenzo's program a bit to see how
the system behaves and how it can be improved.

regards,

Rik

-- 
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