Re: [RFC] CPU hard limits

Bharata B Rao
2009-06-05T06:33:44Z

On Fri, Jun 05, 2009 at 09:03:37AM +0300, Avi Kivity wrote:
> Balbir Singh wrote:
>>> 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.
>>
>
> So the groups with guarantees get a priority boost. That's not a good
> side effect.

That happens only in the presence of idle cycles when other groups [with or
without guarantees] have nothing useful to do. So how would that matter
since there is nothing else to run anyway ?

Regards,
Bharata.