so the hard problem is that on going idle, the local timers need to be
funneled to the external HPET. Afaik right now we use one channel of
the hpet, with the result that we have one global lock for this.

HPETs have more than one channel (2 or 3 historically, newer chipsets
iirc have a few more), so in principle we can split this lock at least
a little bit... if we can get to one hpet channel per level 3 cache
domain we'd already make huge progress in terms of cost of the
contention....

I suggested the same thing a few emails up @) (great minds think 
alike etc.etc. @) . 

I'm not sure how difficult it would be to implement though.

Potential issues:

Some user applications use the hpet channels directly through
the character device interface so there would be a potential
compatibility issue (but maybe that should be just moved
to be emulated with a hrtimer ?)

And if multiple broadcast controllers are elected this might
make it harder to become idle.

-Andi