Re: [PATCH] Add fast little-endian switch system call

[Wolfgang Denk <wd-ynQEQJNshbs@public.gmane.org>]

In message <18454.35824.527711.355488-UYQwCShxghk5kJ7NmlRacFaTQe2KTcn/@public.gmane.org> you wrote:
> 
> > Am I missing something here or does this add a branch for every normal
> > syscall?
> 
> It does, but the impact is so small as to be unmeasurable with
> lmbench, even on the null syscall measurement.  The overhead of the
> easily-predicted not-taken branch is completely swamped by the amount
> of time that the sc and rfid instructions take.  I had it under a
> config option at one point but then decided not to bother with that
> when I couldn't measure any difference.

This probably depends a bit on  the  performance  of  the  system  in
question. Did you measure it - for example - on a 50 MHz MPC850 ?

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd-ynQEQJNshbs@public.gmane.org
To get something done, a committee should consist  of  no  more  than
three men, two of them absent.