Jan Glauber wrote: > This patch introduces a cpu time clock for s390 (only ticking > if the virtual cpu is running) and bases the s390 implementation > of sched_clock() on it. > > The times lice length on a virtual cpu can be anything > between the calculated time slice and zero. In reality > this doesn't seem to be problem, since the scheduler is fair > enough to not let a single process starve but the current > implementation can lead to inefficient short time slices. > > By providing a 'virtual' sched_clock() we guarantee that a > process can get its time slice regardless of scheduling > decisions from the hypervisor. > > Patch applies to 2.6.22 git and works fine with CFS. >
The Xen sched_clock implementation is very similar, and it seems to work well. > /* > - * 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). J - 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/