Re: [libvirt] [PATCH 06/10] vcpubandwidth: introduce two new libvirt APIs
On 07/05/2011 02:06 AM, Wen Congyang wrote:
At 07/04/2011 07:19 PM, Nikunj A. Dadhania Write:
> On Thu, 30 Jun 2011 11:13:18 +0800, Wen Congyang <wency(a)cn.fujitsu.com> wrote:
>> We want to control bandwidth for each vcpu, so we can not use the
>> API virDomainSetSchedulerParameters(). Introduce two new APIs to
>> change and query bandwidth for each vcpu.
>>
> Will we have different cpu bandwidth for different vcpus?
>
> Something like this:
>
> vcpu1: 1000000/250000
> vcpu2: 1000000/500000
> vcpu3: 1000000/300000
> vcpu4: 1000000/400000
>
> IMO, that is not required, we can have a top level bandwitdh for the VM
> and then redistribute it among vcpus equally, without user knowing about
> it.
>
> Something like this:
>
> VM1(4vcpu) has to be throttled at 1CPU bandwidth using SetSchedParamters.
>
> Internally libvirt splits it equally:
> vcpu1: 1000000/250000
> vcpu2: 1000000/250000
> vcpu3: 1000000/250000
> vcpu4: 1000000/250000
>
> So why introduce VCPU level apis?
Adam Litke said IBM's performance team nead to control cpu bandwidth for each
vcpu.
Nikunj is correct here. We only need to ensure that the bandwidth is
distributed equally between all of the cpus. This can be accomplished
internally by creating a cgroup for each vcpu and ensuring that
'cpu.share' is the same for each vcpu cgroup.
--
Adam Litke
IBM Linux Technology Center