82xx performance

[Rune Torgersen]

Arnd Bergmann wrote:
> Ok, I think this could be related mostly to two changes:
> 
> * In 2.6.23, the process scheduler was replaced, the new one
> is the CFS,
> the 'completely fair scheduler'. This has changed a lot of data.
> To verify this, you could check out a git version just before and
> just after CFS went in. 

I'll check. Checking the context switch is fairly fast, so this is a
goot time to learn bisect...

> * Obviously, the 6 percent change between ppc and powerpc should not
> be there. You can still try to use 'readprofile', or oprofile in
> timer based mode (i.e. without HW performance counters) to get some
> more data about where the time is spent on an identical
> kernel version.

I did run oprofile, but I could not figure out how to get it to show me
where in the kernel it was spending time. It showed that a lot of time
was spent in vmlinux, but not anything specific. I probably just don't
know how to set up or run oprofile correctly.