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

[Andi Kleen]

On Thu, 11 Sep 2003 17:58:45 +0100
Jamie Lokier <jamie@xxxxxxxxxxxxx> wrote:

> Andi Kleen wrote:
> > +static int is_prefetch(struct pt_regs *regs, unsigned long addr)
> 
> Do I understand that certain values of "addr" can't be due to the
> erratum?
> 
> In which case, could you skip most of the is_prefetch() instruction
> decoder with a test like this?:
> 
> 	if ((addr & 3) == 0)
> 		return 0;

Maybe. But gcc generates quite good code (binary decision tree) code for
the switch() statement already so I don't think it is worth it to go 
through complications just to avoid that.

The decoder looks big in C, but when you take a look at its hot path in 
assembly it is quite fast.

-Andi
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