Re: [libvirt] [PATCH 5/6] qemu: Implement hypervisor's period and quota tunable XML configuration and parsing
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.
Thanks
Wen Congyang
Limit vm, vcpus and hypervisor. I'm not sure how cpu cgroup behaves
in this case, but I suppose vcpus' and hypervisor's values will not
exceed vm's value.