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Re: [libvirt] [PATCH 5/6] qemu: Implement hypervisor's period and quota tunable XML configuration and parsing



(2012/05/17 15:05), Wen Congyang wrote:

> At 05/17/2012 01:42 PM, Hu Tao Wrote:
>> On Thu, May 17, 2012 at 01:25:48PM +0800, Wen Congyang wrote:
>>> At 05/17/2012 01:09 PM, KAMEZAWA Hiroyuki Wrote:
>>>> (2012/05/17 14:07), Wen Congyang wrote:
>>>>
>>>>> At 05/17/2012 12:46 PM, KAMEZAWA Hiroyuki Wrote:
>>>>>> (2012/05/17 12:54), Wen Congyang wrote:
>>>>
>>>>>>> So, if we donot limit the hypervisor, the behavior shoule not be
>>>>>>> changed. So we should limit the whole vm. If the hypervisor threads
>>>>>>> are limited, there is no need to limit the whole vm.
>>>>>>>
>>>>>>
>>>>>>
>>>>>> need to tune hypervisor quota to limit vcpu-only quota ?
>>>>>> Sounds strange to me.
>>>>>
>>>>> No, current implemetion is:
>>>>> 1. limit vcpu and hypervisor: vm is not limited
>>>>> 2. limit vcpu only: vm is limited
>>>>> 3. limit hypervisor: vm is not limited
>>>>> 4. vcpu and hypervisor are not limited: vm is not limited.
>>>>>
>>>>
>>>>
>>>> In 2.
>>>>
>>>>    vm               ----- quota_is_limited
>>>>     |- hypervisor   ----- quota is unlimited
>>>>     |- vcpu[0...x]  ----- quota is limited
>>>>
>>>> Hm...vm is limited. It seems user need to tune vm's quota...can user
>>>> makes vm's quota to be unlimited and limit *only* vpcus as Xen ?
>>>
>>> Without this patchset, the vm will be limited if the vcpu is limited.
>>> We cannot know whether the hypervisor is unlimited or the user does not
>>> set it. If the user does not set it, we should not change the behavior.
>>> So I donot find an easy way to limit only vcpus.
>>
>> Can we change the implementation like these:
>>
>> 1. 
>> <cputune>
>>   <vcpu>
>>     <period>period</period>
>>     <quota>quota</quota>
>>   </vcpu>
>> </cputune>
>>
>> Limit vcpus only, does not limit vm or hypervisor.
>>
>> 2.
>> <cputune>
>>   <hypervisor>
>>     <period>period</period>
>>     <quota>quota</quota>
>>   </hypervisor>
>> </cputune>
>>
>> Limit hypervisor only, does not limit vm or vcpus.
>>
>> 3.
>> <cputune>
>>   <period>period</period>
>>   <quota>quota</quota>
>> </cputune>
>>
>> Limit the whole vm, in this case vcpus and hypervisor are also limited.
>>
>> 4.
>> <cputune>
>>   <period>period</period>
>>   <quota>quota</quota>
>>   <vcpu>
>>     <period>period</period>
>>     <quota>quota</quota>
>>   </vcpu>
>>   <hypervisor>
>>     <period>period</period>
>>     <quota>quota</quota>
>>   </hypervisor>
>> </cputune>
> 
> This is very complex, and the user should know how we implement it
> and the period/quota's limit. If the user gives a wrong value, the
> vm cannot start.
> 
> We implement the limit like this:
> 
>               vm
>                |
>  ----------------------------
>  |       ...         |       |
> vcpu0               vcpun   hypervisor
> 
> If all is limited, the vm's quota should be greater than max(vcpu's quota, hypervisor's quota)
> and vm's period should be less than min(vcpu's period, hypervisor's period).
> 
> So I donot like this idea.
> 
 

Hmm. my proposal is not so complicated as you say. And simpler than your way.

  <quota target='all|vcpu'>   </quota> # all is default and limit the whole vm.
                                       # vcpu is just limit vcpus rather than whole vm.
  <period> .... </period>              # period is shared in all settings.

Isn't it ?

Thanks,
-Kame



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