Re: adding accuracy to random timers on PPC - new config option or runtime overhead?

[Chris Friesen <cfriesen@nortelnetworks.com>]

Ignacio Vazquez-Abrams wrote:
> 
> On Wed, 22 Aug 2001, Chris Friesen wrote:
> > I'm looking at putting in PPC-specific code in add_timer_randomness() that would
> > be similar to the x86-specific stuff.
> >
> > The problem is that the PPC601 uses real time clock registers while the other
> > PPC chips use a timebase register, so two different versions will be required.
> > Should I try and identify at runtime which it is (which would be extra
> > overhead), or should I add another config option to the kernel?

> How about determining which one to use at boot time? That way there's no
> overhead, and there's no need to have yet another config option which probably
> doesn't need to be there.

As far as I can see there will still be some extra overhead.  We'd need an extra
conditional that wouldn't be there with the config option.  Granted, one
conditional shouldn't be too expensive, especially since we'll always be picking
the same branch.

-- 
Chris Friesen                    | MailStop: 043/33/F10  
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