Re: [libvirt] [RFC] Add persistent XML for cpu tunables

On Tue, 29 Mar 2011 15:31:19 +0800, Daniel Veillard&lt;veillard(a)redhat.com&gt; wrote: > On Tue, Mar 29, 2011 at 02:32:18PM +0800, Osier Yang wrote: >> Example of cputune XML: >> <cputune> >> <shares>2048</shares> >> <vcpupin vcpu='0' cpuset='0-4,^1'/> >> <vcpupin vcpu='1' cpuset='1,3'/> >> <vcpupin vcpu='2' cpuset='0,2'/> >> </cputune> >> >> "shares" is to define the the proportional weighted cpu share >> for the domain. > > Hum, what does "2048" there means ? I assume there is an unit but > it's not defined. Can we get a precide definition of the semantic of > the shares construct. If I were to use it I need to know what it means, > and I can't just from that description. Drivers in QEmu and LXC just > pass that down to linux, but it still doesn't provide a semantic for > it and "whatever linux implements at the time" is not really a good > answer. > The number is relative wrt other domains/cgroup, so if we have two VMs each having 2048, both of them will get equal share, i.e. 50% each. In a different scenario, if we have VM1's share as 1024 and VM2's share as 2048, that translates as VM1=33% and VM2=66% share of the CPU.

Regards Nikunj