Re: K7/Athlon optimizations and Sacrifices to the Great Ones.

Alan Cox (alan@lxorguk.ukuu.org.uk)
Fri, 7 Sep 2001 21:52:27 +0100 (BST)


> I did some trial and error modifications to mmx.c and found out
> that this one makes my athlons happy (but must admin i have
> no clue why). it seems to run stable now.
>
> --- linux-2.4.9/arch/i386/lib/mmx.c Tue May 22 19:23:16 2001
> +++ linux-2.4.9-ac6-hack/arch/i386/lib/mmx.c Sat Sep 8 00:51:33 2001
> @@ -194,6 +194,9 @@
> : : "r" (from), "r" (to) : "memory");
> from+=64;
> to+=64;
> + __asm__ __volatile__ (
> + " sfence \n" : :
> + );
> }
> for(i=(4096-320)/64; i<4096/64; i++)
> {
>

You are effectively continually stalling the processor so that the fast
streaming memory transfers dont occur. Instead you start, block, start,
block, ...

Alan
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