* Avi Kivity <avi@xxxxxxxxxx> [2010-12-13 13:57:37]: > On 12/11/2010 03:57 PM, Balbir Singh wrote: > >* Avi Kivity<avi@xxxxxxxxxx> [2010-12-11 09:31:24]: > > > >> On 12/10/2010 07:03 AM, Balbir Singh wrote: > >> >> > >> >> Scheduler people, please flame me with anything I may have done > >> >> wrong, so I can do it right for a next version :) > >> >> > >> > > >> >This is a good problem statement, there are other things to consider > >> >as well > >> > > >> >1. If a hard limit feature is enabled underneath, donating the > >> >timeslice would probably not make too much sense in that case > >> > >> What's the alternative? > >> > >> Consider a two vcpu guest with a 50% hard cap. Suppose the workload > >> involves ping-ponging within the guest. If the scheduler decides to > >> schedule the vcpus without any overlap, then the throughput will be > >> dictated by the time slice. If we allow donation, throughput is > >> limited by context switch latency. > >> > > > >If the vpcu holding the lock runs more and capped, the timeslice > >transfer is a heuristic that will not help. > > Why not? as long as we shift the cap as well. > Shifting the cap would break it, no? Anyway, that is something for us to keep track of as we add additional heuristics, not a show stopper. -- Three Cheers, Balbir -- 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
