RE: [PATCH] 2.6 workaround for Athlon/Opteron prefetch errata

richard.brunner
2003-09-11T17:33:40Z

> -----Original Message-----
> From: Andi Kleen [mailto:ak@suse.de]
> Sent: Thursday, September 11, 2003 7:29 AM
>
> On Thu, 11 Sep 2003 15:14:51 +0100
> Dave Jones <davej@redhat.com> wrote:
>
> > On Thu, Sep 11, 2003 at 04:01:08PM +0200, Andi Kleen wrote:
> >
> > > > What's wrong with the current status quo that just says
> > > > "Athlon prefetch is broken"?
> > > It doesn't fix user space for once.
> >
> > And for another, it cripples the earlier athlons which
> > don't have this
> > errata. Andi's fix at least makes prefetch work again on
> > those boxes.
> > It's also arguable that prefetch() helps the older K7's
> > more than the
> > affected ones.
>
> All Athlons have this Errata. I can trigger it on an old
> 900Mhz pre XP Athlon too. You just have to use 3dnow prefetch
> instead of SSE prefetch.
>
> BTW the older Athlons currently don't use prefetch because
> the alternative
> patcher does not handle 3dnow style prefetch.
>

Avoiding prefetch for all Athlons and earlier Opterons/Athlon64
even in the kernel can really tank performance. And as Andi says
it still doesn't solve user mode from hitting the errata.

] -Rich ...
] AMD Fellow