On 10/04/2012 12:56 PM, Raghavendra K T wrote:
> On 10/03/2012 10:55 PM, Avi Kivity wrote:
>> On 10/03/2012 04:29 PM, Raghavendra K T wrote:
>>> * Avi Kivity <avi@xxxxxxxxxx> [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.
Right. Prioritize vcpus that are cheap to yield to. But may return bad
results if all vcpus on the current runqueue are spinners, so probably
not a good idea.
> Does it add more overhead especially in <= 1x scenario?
The current runqueue should have just our vcpu in that case, so low
overhead. But it's a bad idea due to the above scenario.
--
error compiling committee.c: too many arguments to function
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