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SubjectRe: 2.6.0-test3-mm1: scheduling while atomic (ext3?)
On Wed, Aug 13, 2003 at 07:44:24PM +0100, Alan Cox wrote:
> On Mer, 2003-08-13 at 16:32, Andi Kleen wrote:
> > The AMD slides assume all very big data sets ;-)
> >
> > I would recommend to remove it.
>
> I'll do some timings when I get a moment - the prefetching mmx copy

Microbenchmarks are useless for this. You have to bench the users too,
otherwise you don't recognize the additional cache misses.

> was a win (and faster than the others for small data as well as large
> on the K7-550 (really a K7 not "Athlon" 8)) way back when.

Possible. In my experience the best copy functions vary widly between
different steppings. Just optimizing for a single one is probably
not a good idea, especially not for an very old one
(except when you add dynamic patches for the different steppings, but
then it quickly gets ugly with too many variants)

When in doubt use the more simple function.

-Andi
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