On 09/24/2012 05:41 PM, Avi Kivity wrote: > >> >> case 2) >> rq1 : vcpu1->wait(lockA) (spinning) >> rq2 : vcpu3 (running) , vcpu2->holding(lockA) [scheduled out] >> >> I agree that checking rq1 length is not proper in this case, and as you >> rightly pointed out, we are in trouble here. >> nr_running()/num_online_cpus() would give more accurate picture here, >> but it seemed costly. May be load balancer save us a bit here in not >> running to such sort of cases. ( I agree load balancer is far too >> complex). > > In theory preempt notifier can tell us whether a vcpu is preempted or > not (except for exits to userspace), so we can keep track of whether > it's we're overcommitted in kvm itself. It also avoids false positives > from other guests and/or processes being overcommitted while our vm is fine. It also allows us to cheaply skip running vcpus. We would probably need a ->sched_exit() preempt notifier to make this work. Peter, I know how much you love those, would it be acceptable? We'd still need yield_to() but the pressure on it might be reduced. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
