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Re: [Xen-devel] Xen cpu Scheduling


xentop gets information from runstate (see vcpu_runstate_change())
Please check it.

Atsushi SAKAI

pak333@xxxxxxxxxxx wrote:

> Hi,
> I have some questions on scheduling. 
> 1. Suppose I give a VM 2 vcpus. When this VM gets scheduled will it always be 
> given two pcpus or can it be given 1vcpu also sometimes.  For example if we 
> have mutiple VMs running, and if a cpu gets freed up will my 2vcpu VM be 
> scheduled on this single free cpu.  If a single cpu cna be given how is the 
> cpu % calculated by xentop
> 2. If the 2vcpu is scheduled on two cpus, and one of its threads goes to 
> sleep can that single thread be context swtiched out. or will it be kept 
> spinning.
> 3. When xentop reports VM cpu% as say 167% what does that mean. is it the % 
> of time for the 2 vcpus (that means the VM is using 167% of the 200% it was 
> allotted, or is the 167% of the number of pcpus in the system), or is it 167% 
> of the total number of vcpus.
> Thanks much for answering my questions
> - Prabha

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