On 09/25/2012 03:40 PM, Raghavendra K T wrote: > On 09/24/2012 07:46 PM, Raghavendra K T wrote: >> On 09/24/2012 07:24 PM, Peter Zijlstra wrote: >>> On Mon, 2012-09-24 at 18:59 +0530, Raghavendra K T wrote: >>>> However Rik had a genuine concern in the cases where runqueue is not >>>> equally distributed and lockholder might actually be on a different run >>>> queue but not running. >>> >>> Load should eventually get distributed equally -- that's what the >>> load-balancer is for -- so this is a temporary situation. >>> >>> We already try and favour the non running vcpu in this case, that's what >>> yield_to_task_fair() is about. If its still not eligible to run, tough >>> luck. >> >> Yes, I agree. >> >>> >>>> Do you think instead of using rq->nr_running, we could get a global >>>> sense of load using avenrun (something like avenrun/num_onlinecpus) >>> >>> To what purpose? Also, global stuff is expensive, so you should try and >>> stay away from it as hard as you possibly can. >> >> Yes, that concern only had made me to fall back to rq->nr_running. >> >> Will come back with the result soon. > > Got the result with the patches: > So here is the result, > > Tried this on a 32 core ple box with HT disabled. 32 guest vcpus with > 1x and 2x overcommits > > Base = 3.6.0-rc5 + ple handler optimization patches > A = Base + checking rq_running in vcpu_on_spin() patch > B = Base + checking rq->nr_running in sched/core > C = Base - PLE > > ---+-----------+-----------+-----------+-----------+ > | Ebizzy result (rec/sec higher is better) | > ---+-----------+-----------+-----------+-----------+ > | Base | A | B | C | > ---+-----------+-----------+-----------+-----------+ > 1x | 2374.1250 | 7273.7500 | 5690.8750 | 7364.3750| > 2x | 2536.2500 | 2458.5000 | 2426.3750 | 48.5000| > ---+-----------+-----------+-----------+-----------+ > > % improvements w.r.t BASE > ---+------------+------------+------------+ > | A | B | C | > ---+------------+------------+------------+ > 1x | 206.37603 | 139.70410 | 210.19323 | > 2x | -3.06555 | -4.33218 | -98.08773 | > ---+------------+------------+------------+ > > we are getting the benefit of almost PLE disabled case with this > approach. With patch B, we have dropped a bit in gain. > (because we still would iterate vcpus until we decide to do a directed > yield). This gives us a good case for tracking preemption on a per-vm basis. As long as we aren't preempted, we can keep the PLE window high, and also return immediately from the handler without looking for candidates. -- 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
