libvirt users - Apr 2015 - Re: CPU Resource Reservation using KVM

Hi All

I am new to KVM world. I have been using VMware for about a year.

In VMware world we can reserve cpu resources for a VM. Say for instance 
if we need 4 vCPUs with a total of 8000 GHz then we can mention this 
configuration in vCenter while creating a VM. This guarantees 8000 GHz 
of cpu resources for the deployed VM.

How can i achieve the same thing using KVM ?

Please provide as much details as possible. Any pointers for reading 
this would also be helpful.

Appreciate your responses in this regard.

Thanks
Jatin

On Mon, Apr 13, 2015 at 12:14:12PM +0530, Jatin Davey
wrote:
> Hi All
> 
> I am new to KVM world. I have been using VMware for about a year.
> 
> In VMware world we can reserve cpu resources for a VM. Say for instance if
> we need 4 vCPUs with a total of 8000 GHz then we can mention this
> configuration in vCenter while creating a VM. This guarantees 8000 GHz of
> cpu resources for the deployed VM.
>
> How can i achieve the same thing using KVM ?
 
If you are comfortable with command line, you can look at `virsh` manual
page for 

    setvcpus - change number of virtual CPUs

to control how many vCPUs you can allocate.

If you're using `virt-manager`, you should be able to control it via UI
for a guest under its "Show virtual hardware details" and look for
"Processor".


-- 
/kashyap

On 4/13/2015 1:18 PM, Kashyap Chamarthy wrote:
> On Mon, Apr 13, 2015 at 12:14:12PM +0530, Jatin Davey wrote:
>> Hi All
>>
>> I am new to KVM world. I have been using VMware for about a year.
>>
>> In VMware world we can reserve cpu resources for a VM. Say for instance
if
>> we need 4 vCPUs with a total of 8000 GHz then we can mention this
>> configuration in vCenter while creating a VM. This guarantees 8000 GHz
of
>> cpu resources for the deployed VM.
>>
>> How can i achieve the same thing using KVM ?
>   
> If you are comfortable with command line, you can look at `virsh` manual
> page for
>
>      setvcpus - change number of virtual CPUs
>
> to control how many vCPUs you can allocate.
>
> If you're using `virt-manager`, you should be able to control it via UI
> for a guest under its "Show virtual hardware details" and look
for
> "Processor".
>
>
I have looked at virsh and more specifically "setvcpus". We can assign
virtual CPUs using it but my question is different. I am looking at 
reserving cpu speed to the virtual cpu's. I know we can allocate and 
modify the amount vcpu's using setvcpus command but how can i ask kvm to 
reserve a particular amount of cpu speed of the host core's to the 
virtual cpus.

Thanks
Jatin