Messages in this thread | | | Date | Wed, 22 Aug 2001 13:57:31 -0400 (EDT) | From | Ignacio Vazquez-Abrams <> | Subject | Re: adding accuracy to random timers on PPC - new config option or runtime overhead? |
| |
On Wed, 22 Aug 2001, Chris Friesen wrote:
> 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.
If the versions of the functions aren't too large then you may be able to get away with putting in both functions and then using a function pointer to select which one to use.
-- Ignacio Vazquez-Abrams <ignacio@openservices.net>
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |