Messages in this thread | | | Date | Thu, 04 Oct 2012 16:26:36 +0530 | From | Raghavendra K T <> | Subject | Re: [PATCH RFC 0/2] kvm: Improving undercommit,overcommit scenarios in PLE handler |
| |
On 10/03/2012 10:55 PM, Avi Kivity wrote: > On 10/03/2012 04:29 PM, Raghavendra K T wrote: >> * Avi Kivity <avi@redhat.com> [2012-09-27 14:03:59]: >> >>> On 09/27/2012 01:23 PM, Raghavendra K T wrote: >>>>> >> [...] >>>> 2) looking at the result (comparing A & C) , I do feel we have >>>> significant in iterating over vcpus (when compared to even vmexit) >>>> so We still would need undercommit fix sugested by PeterZ (improving by >>>> 140%). ? >>> >>> Looking only at the current runqueue? My worry is that it misses a lot >>> of cases. Maybe try the current runqueue first and then others. >>> >> >> Okay. Do you mean we can have something like >> >> + if (rq->nr_running == 1 && p_rq->nr_running == 1) { >> + yielded = -ESRCH; >> + goto out_irq; >> + } >> >> in the Peter's patch ? >> >> ( I thought lot about && or || . Both seem to have their own cons ). >> But that should be only when we have short term imbalance, as PeterZ >> told. > > I'm missing the context. What is p_rq?
p_rq is the run queue of target vcpu. What I was trying below was to address Rik concern. Suppose rq of source vcpu has one task, but target probably has two task, with a eligible vcpu waiting to be scheduled.
> > What I mean was: > > if can_yield_to_process_in_current_rq > do that > else if can_yield_to_process_in_other_rq > do that > else > return -ESRCH
I think you are saying we have to check the run queue of the source vcpu, if we have a vcpu belonging to same VM and try yield to that? ignoring whatever the target vcpu we received for yield_to.
Or is it that kvm_vcpu_yield_to should now check the vcpus of same vm belonging to same run queue first. If we don't succeed, go again for a vcpu in different runqueue. Does it add more overhead especially in <= 1x scenario?
| |