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

Andi Kleen
2003-09-12T17:56:13Z

On 12 Sep 2003 11:32:42 -0600
ebiederm@xmission.com (Eric W. Biederman) wrote:

> There may be better places to attack. But new code is what is up for
> examination and is easiest to fix.

With is_prefetch:

text data bss dec hex filename
2782 4 0 2786 ae2 arch/i386/mm/fault.o

Without is_prefetch:

text data bss dec hex filename
2446 4 0 2450 992 arch/i386/mm/fault.o

Difference 332 bytes

If you start your attack on 332 bytes then IMHO you have your priorities wrong ;-)

The main reason I'm really against this is that currently the P4 kernels work
fine on Athlon. Just when is_prefetch is not integrated in them there will
be an mysterious oops once every three months in the kernel in prefetch
on Athlon.

That would be bad. The alternative would be to prevent the P4 kernel
from booting on the Athlon at all, but doing that for 332 bytes
would seem a bit silly.

-Andi

P.S.: If you really want to shrink 2.6 I would start with making sysfs optional.
That would likely help much more than micro optimizing non bloated parts.