On Thu, 2007-07-19 at 18:00 +0200, Ingo Molnar wrote: > * Jeremy Fitzhardinge <[EMAIL PROTECTED]> wrote: > > > > /* > > > - * Monotonic_clock - returns # of nanoseconds passed since time_init() > > > + * Scheduler clock - returns current time in nanosec units. > > > + * Now based on virtual cpu time to only account time the guest > > > + * was actually running. > > > > Runn*ing*? Does it include time the VCPU spends idle/blocked? If > > not, then the scheduler won't be able to tell how long a process has > > been asleep. Maybe this doesn't matter (I had this problem in a > > version of Xen's sched_clock, and I can't say I saw an ill effects > > from it).
No, it does not include idle time, if we're going idle the cpu timer gets stopped. > CFS does measure time elapsed across task-sleep periods (and does > something similar to what the old scheduler's 'sleep average' > interactivity mechanism did), but that mechanism measures "time spent > running during sleep", not "time spent idling". > > still, CFS needs time measurement across idle periods as well, for > another purpose: to be able to do precise task statistics for /proc. > (for top, ps, etc.) So it's still true that sched_clock() should include > idle periods too. I'm not sure, s390 already has an implemetation for precise accounting in the architecture code, does CFS also improve accounting data? Jan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
