Re: [RFC] [PATCH] cache pollution aware __copy_from_user_ll()

Andi Kleen
2005-08-24T16:18:43Z

Hiro Yoshioka <hyoshiok@miraclelinux.com> writes:

> Hi,
>
> The following patch does not use MMX regsiters so that we don't have
> to worry about save/restore the FPU/MMX states.
>
> What do you think?

Performance will probably be bad on K7 Athlons - those have a microcoded
movnti which is quite slow.

Also BTW I don't see any code anywhere that tests the CPUID bits,
so your code will fail spectacularly on a PII that didn't do SSE
(intel user copy used to be enabled on those)

One way to solve this might be to use different code using
alternative()

-Andi