On Wed, 5 Jan 2005, Christian Limpach wrote:
> On Wed, Jan 05, 2005 at 09:06:10AM -0600, Andrew Theurer wrote:
> > >I don't think there's significant overhead if there's only a single
> > >virtual cpu pinned to one physical cpu so I wouldn't expect a noticeable
> > >performance advantage if we handled this case differently.
> > >
> > Hopefully soon I can get some performance tests going and we can see if
> > there's any issues here. My other concern would be on larger (multi
> > numa-node) systems, even with one to one mapping, that the hardware
> > topology (numa) information does not make it to the SMP guest -it would
> > be nice to take advantage of the numa work developed in the linux kernel
> > over that last 2 years. I am not sure exactly what impact this could be.
>
> Yes, this is probably even needed on 2-cpu with 2 hyperthreads systems.
> Right now, all virtual cpus are presented as independent physical cpus
> to the domains and the domains can't easily tell if two virtual cpus
> run on different physical cpus, on different hyperthreads on the same
> cpu or on the same hyperthread. If we export this information to the
> guest, we'll then probably also have to have a way to inform the guest
> if a virtual cpu is moved to a different hyperthread or physical cpu.
Also consider the NUMA equation.
Search l-k for cpusets.
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