Improved copy_page() function, about 30% speed up for mpc860!

[Joakim Tjernlund]

> Hi all
>
> I have been playing with the copy_page() function in arch/ppc/kernel/misc.S
> and gained about 30% speed up for my mpc860, rev D4 MHz.
>
> This is what i did:
> - Use dcbz on 8xx but clear ahead one cache line(performance is really crappy
>   if I don't clear ahead). This is the biggest improvement.
> - Use prefetch for 8xx as well.
>
> I know that dcbz is buggy for some 8xx CPUs but I don't know which ones.
> For me works just fine, except in copy_tofrom_user(don't know why).

hmm, I made two versions of copy_tofrom_user(), copy_from_user() and copy_to_user()
and modified asm/uaccess.h to reflect this.
Then I modified copy_from_user() to use dcbz on the destination area.
Booted and started our app and it works just fine!

 Jocke


** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/