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

[Andi Kleen]

Hiro Yoshioka <hyoshiok@xxxxxxxxxxxxxxxx> 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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/