On Thursday 19 June 2008, Paul Mackerras wrote:
> Arnd Bergmann writes:
>
> > Have you tried running this code on other platforms to see if it
> > actually performs worse on any of them? I would guess that the
> > older code also doesn't work too well on Power 5 and Power 6,
>
> Why would you guess that?
I remembered that Gunnar had done some tests on other CPUs showing
that an earlier version of the code was better than the kernel
memcpy.
Also, I had tried to trace the history of the usercopy function
and found that it predates most of the CPUs in current use, so
I assume it has suffered from bitrot and nobody tried to do better
since the Power3 days. AFAICT, it hasn't seen any update since your
original Power4 version from 2002.
Arnd <><
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