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

[bill davidsen]

In article <20030911162421.419f4432.ak@xxxxxxx>,
Andi Kleen  <ak@xxxxxxx> wrote:
| On Thu, 11 Sep 2003 15:14:02 +0100
| Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> wrote:
| 
| > 
| > There is *one* change needed. We shouldnt call is_prefetch unless the
| > current CPU is an Athlon. That way its a performance improvement for
| > PIV, and Athlon in general, fixes the bug and causes no fancy athlon
| > fixup code for non AMD processors.
| 
| I considered that when writing the patch, but: is_prefetch is a single byte 
| memory access for something already in cache. Checking for an Athlon
| CPU needs two memory accesses in boot_cpu_data at least (checking vendor
| and model) 

You are still missing the point, what's needed is not a better way to do
useless work, it's a way to avoid doing it at all. This code should only
be built for CPU's which need it, no accesses needed except in .config.
-- 
bill davidsen <davidsen@xxxxxxx>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.
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