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



At 05/17/2012 02:06 PM, KAMEZAWA Hiroyuki Wrote:
> (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 ?

Do you mean this:
<cputune>
  <vcpu>
    <period>period</period>
    <quota target='all|vcpu'>quota</quota>
  </vcpu>
  <hypervisor>
    <period>period</period>
    <quota>quota</quota>
  </hypervisor>
</cputune>

Thanks
Wen Congyang
> 
> Thanks,
> -Kame
> 
> 
> 


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