Re: [libvirt] [PATCH 06/10] vcpubandwidth: introduce two new libvirt APIs

On Wed, 06 Jul 2011 14:56:27 +0800, Gui Jianfeng <guijianfeng(a)cn.fujitsu.com&gt; wrote: > On 2011-7-5 16:41, Nikunj A. Dadhania wrote: >> On Tue, 05 Jul 2011 15:06:06 +0800, Wen Congyang <wency(a)cn.fujitsu.com&gt; 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&gt; 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. >> Right, but we do not export that as a User API, that was my suggestion. >> We can internally control each vcpu's bandwidth, i.e. divide equally. > > Hmm, I heard that some server could run CPUs at different speed. > May be this patch can simulate this behavior. That happens on my laptop as well, depending on the machine load CPU frequency is changed but it is done transparently.

I am not sure if we are trying to simulate that here.

Regards Nikunj