On 27 Apr 2017, at 16:29, Nelson Lameiras <nelson.lameiras@lyra-network.com> wrote:

Hello oVirt gurus,

When activating/deactivating memory balloning on VM, this will change /usr/libexec/qemu-kvm command line on host on vm startup (you can see it using "ps aux").
So I understand a vm reboot is needed to take this change into account.

Right. That option controls the presence of the virtio-balloon device which is not hotpluggable 


But when activating/deactivating memory balloning on Cluster (plus MoM Sync on host) I do not really understand what happens "under the hood"

This controls the actual behavior, inflating and deflating of those balloons. That can be done in runtime as it is external to the VM, managed by MOM demon. 


- Is there a mechanism on host which controls "memory balloning" globally?
- Is it able to change it's behaviour "on the fly" with "MoM Sync" ?

Yes. You can change the policy/behavior. 

HTH,
michal


If you have any information, it would be greatly appreciated

cordialement, regards,

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Nelson LAMEIRAS
Ingénieur Systèmes et Réseaux / Systems and Networks engineer
Tel: +33 5 32 09 09 70
nelson.lameiras@lyra-network.com
www.lyra-network.com | www.payzen.eu
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