Re: Promblem with PREF (prefetching) in memcpy

["Kevin D. Kissell" <kevink@mips.com>]

From: "Alan Cox" <alan@lxorguk.ukuu.org.uk>
> On Fri, 2002-10-04 at 14:15, Kevin D. Kissell wrote:
> > Which is excatly the point that Carsten was raising when he started this 
> > thread!
> > 
> > The question is how, i.e. throttle memcpy or thow away a "guard band" of 
> > RAM?
> 
> 
> The x86 code basically says
> 
> while(over 320 bytes left)
> {
> prefetch ahead
> copy bits
> }
> while(bytes left)
> copy bits

Which is safe, simple, and efficient, but does seem to have the property
that there's a "cursed" page in the system that can be randomly allocated
and which will be curiously slow on memcopy().  That might or might not
be a problem in the embedded application space.

            Regards,

            Kevin K.