P4s, Athlons and bandwidth

[Alan Cox]

> There is a business case: if, for instance, Linux is left in the dust at
> web serving because Apache uses memcpy significantly and Linux's memcpy
> is three or four times slower on a P4 than the version used by W2K.

If apache is block copying 32K chunks around then there is a much better
cure - fixing apache. It isnt "lets do big memory copies fast" first of
all but "why am I doing big memory copies".

In the case of the PIV I've also seen little evidence to suggest any 
meaningful different between rep movs and fancy stuff even on big blocks
unless you have innate knowledge of cache handling and local use (which
glibc doesn't). Intel seem to have nice silicon fast paths for this stuff