Hi: I've been thinking about how rescheduling interrupts *might* work in Linux and how they relate to powertop's reporting. First, a caveat: I don't understand very much about either Linux kernel internals or Intel hardware.
It seems to me that on *some* hardware, a kernel IPI resulting from rescheduling interrupts shouldn't have any power implications. Consider a Thinkpad T60, which has a twin-code processor. I believe that with this hardware both processors always run at the same speed. This means that running one processor is almost as energy-intensive as running two processors. Since rescheduling interrupts just starts the "idle" processor, almost certainly while the other processor is working, rescheduling interrupts should be in this very-cheap situation. So, given all that, maybe powertop shouldn't be reporting rescheduling interrupts (and thus causing lots of angst) for such hardware. Perhaps powertop could do this in general - not reporting events that don't cost energy. Of course this all depends on whether my analysis is correct. Comments? Peter F. Patel-Schneider PS: Of course, it is still mystifying that rescheduling interrupts can cause more than 50% of wakeups, or even a significant fraction of wakeups with an extremely light load. How can it make sense to wakeup the other core when all the current core is doing is finishing the work needed to service an interrupt. _______________________________________________ Power mailing list [email protected] http://www.bughost.org/mailman/listinfo/power
