Dynamic CPU cores allocation

[ionutr]

Hey,

I was wondering if it's possible to dynamically allocate CPU cores to VMs.
ex: having 4 VMs on a 24 core CPU (6 cores each) and when 3 of the VMs are idling, to re-allocate the unused cores to the 4 VM that has a big load running on it.

Thanks

 

[Stefan_R]

That already happens, automatically. What you're referring to is called "overprovisioning", i.e. you assign more cores to your VMs than you physically have. Then, when a VM isn't using some of it's cores, the performance will be available to others.

In your example, you could assign your 4 VMs 20 cores each, then, if 3 are idle, the 4th will get access to all 20 cores, if all 4 are busy, every VM will get the equivalent of 24/4 = 6 cores. This of course will not show up in a reduced core number, but in overall reduced performance, i.e. the guests will see 20 "slower" cores - but the effect is the same.

There is a limit as to how much you should overprovision of course, at some point your host itself will be overloaded which may cause further issues.

 

[ionutr]

Thanks for the tip. I'll try it