Re: [RFC] CPU hard limits

Balbir Singh
2009-06-05T05:28:26Z

* Avi Kivity <avi@redhat.com> [2009-06-05 08:21:43]:

> Balbir Singh wrote:
>>> But then there is no other way to make a *guarantee*, guarantees come
>>> at a cost of idling resources, no? Can you show me any other
>>> combination that will provide the guarantee and without idling the
>>> system for the specified guarantees?
>>>
>>
>> OK, I see part of your concern, but I think we could do some
>> optimizations during design. For example if all groups have reached
>> their hard-limit and the system is idle, should we do start a new hard
>> limit interval and restart, so that idleness can be removed. Would
>> that be an acceptable design point?
>
> I think so. Given guarantees G1..Gn (0 <= Gi <= 1; sum(Gi) <= 1), and a
> cpu hog running in each group, how would the algorithm divide resources?
>

As per the matrix calculation, but as soon as we reach an idle point,
we redistribute the b/w and start a new quantum so to speak, where all
groups are charged up to their hard limits.

For your question, if there is a CPU hog running, it would be as per
the matrix calculation, since the system has no idle point during the
bandwidth period.

--
Balbir