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 14:00, Kevin D. Kissell wrote:
> > The issue isn't that anyone would deliberately use memcpy() in I/O
> > space.  Rather, it's that memcpy() prefetches quite a ways ahead,
> > and if one has I/O space assigned just after the end of physical
> > memory, Bad Things might happen on a perfectly legal memcpy()
> > that references the last couple hundred bytes of memory in a 
> > way that not even a clever and well-informed bus error handler 
> > could undo.
> 
> Then your memcpy function is IMHO broken. Fix it to note prefetch beyond
> the end of the area you actually will copy and life should be a lot
> better

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?

            Regards,

            Kevin K.