> While you are changing things in this area, it would be nice if you also
   > added a way for cc_microtime and friends to be informed of deliberate
   > changes in CPU speed (such as the i386 "Enhanced SpeedStep" stuff in
   > sys/arch/i386/i386/est.c).
   
   Is it worthwhile? The fallout from not doing it is just inaccurate
   sub-second time estimates until the next cycle-count calibration
   (currently once a second, and here being proposed to be about ten
   seconds). In any case the calibrator needs a full calibration period
   at the new speed before it can do things correctly, so such an update
   call could only reset the calibration timer, saving 1/2 of a
   calibration period.


considering you can end up at less than 1/2 the clock that means you'll
be more than half a second out by the next second.  seems pretty severe,
ie, it needs to be handled correctly...  at 10 second interval, you'd
end up all over the place...



.mrg.