Dividing cpu cycles between processes

[spin_ro]

Hello,

I have an Ubuntu server system on which i want to run multiple virtual machines.
But some VMs are more important than others, and i wish to guarantee them a minimum cpu access (if they need it).

example 1 : if there were 2 VMs, i would like to be able to grant one of them a number of cpu cycles 4 times greater. Also, if one of the machines isn't using all it's allocated cpu time, the other one must be able to use it.
example 2 more complex : if i have N VMs, i want to be able to set for each VM a minimum % of cpu usage. But if a VM doesn't need it, another VM can use it. This way, every VM get at least the % indicated, but can receive more if the other VMs are not using their time.

I know about 'cpulimit' , but it only knows how to set an upper limit. I need something that is flexible at the upper part.

Does anyone have a solution for this ?
Thanks in advance
andrei

[Rubberman]

This is a matter for the scheduler. There are several available for Linux, and which is used by a particular virtual machine manager such as VirtualBox is up to the VMM. VirtualBox uses the standard system scheduler, so you should be able to renice a running VM to a higher priority than the others. You'll need to do some experimenting to find what works best for you.

[Rubberman]

BTW, the lower the nice factor (some number < 0), the higher the priority of the process.