Updating CPU= in Sunstone

Community Support
1

Hello,

if I understand it correctly, the CPU parameter of a VM is only used for determining how many VMs is ONe allowed to cram into a single physical host. And the VCPU parameter means the number of threads qemu starts, which means the number of CPUs the virtual machine can see.

Now why it is not possible to change the CPU parameter of a running VM on the fly in the Sunstone VM -> Capacity tab? I have several VMs which have the CPU parameter set to be equal to VCPU, but the VM in question does not even remotely consume that much CPU. My end-users apparently do not understand the difference between CPU and VCPU, so I need to fix their already running misconfigured VMs.

How do you set up the CPU quotas and how do your users set the CPU parameters on non-computational clusters? Is CPU overcommitment the right solution to this problem?

Thanks!

2

This makes sense for KVM and vCenter, we’ll tackle it for next releases:

https://github.com/OpenNebula/one/issues/1660

3

OK, thanks!

Another related problem: I have a VM which uses - say - 0.2 CPU on average, but needs to handle bursts of load which require - say - 4 CPUs to run smoothly. So I set CPU=0.2 and VCPU=4, but this does not probably guarantee that the VM is scheduled only on hosts with at least four CPU cores. And running it on less cores makes it even slower because of the locking overhead. I can use explicitly set scheduling requirements, but can this be done automatically by the ONe scheduler?

Thanks!