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@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