Kernel 2.6 on MPC8xx performance trouble...
Wolfgang Denk
wd at denx.de
Sat Oct 29 06:37:27 EST 2005
In message <200510281257.22650.david.jander at protonic.nl> you wrote:
>
> > What is 'a' and 'b'? The only other explanation I can see is that your
> > "Do something" is more memory heavy than you think - array calculations?
> > (Cache problems should probably give a worse result, but you could check
> > that those config registers are the same).
>
> They are just integers with fixed start values. These are in the loop, so it's
> not an empty loop and hopefully the compiler won't out-optimize it so easily
> (that is of course without specifying any optimization flags). Please don't
> tell me it's a lousy benchmark, because I already know that! Be it as lousy
> as it is, I shouldn't get _those_ results IMHO.
Indeed, you should not get such results. If you compare with the
lmbench results of our 2.4/2.6 comparison, you will notice that we
did NOT see such behaviour. There was a perfromnce degradation for
pure integer tests, due to increased system overhead, but far from a
factor of 2.
See http://www.denx.de/wiki/pub/Know/Linux24vs26/lmbench_results
Best regards,
Wolfgang Denk
--
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
A fanatic is a person who can't change his mind and won't change the
subject. - Winston Churchill
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