[Qemu-devel] Re: [PATCH] qemu-kvm: response to SIGUSR1 to start/stop a VCPU (v2)

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

On Wed, 2010-12-01 at 14:42 -0500, Rik van Riel wrote:
> On 12/01/2010 02:35 PM, Peter Zijlstra wrote:
> > On Wed, 2010-12-01 at 14:24 -0500, Rik van Riel wrote:
> 
> >> Even if we equalized the amount of CPU time each VCPU
> >> ends up getting across some time interval, that is no
> >> guarantee they get useful work done, or that the time
> >> gets fairly divided to _user processes_ running inside
> >> the guest.
> >
> > Right, and Jeremy was working on making the guest load-balancer aware of
> > that so the user-space should get fairly scheduled on service (of
> > course, that's assuming you run a linux guest with that logic in).
> 
> At that point, you might not need the host side balancing
> any more, since the guest can move around processes
> internally (if needed).

Not quite sure what you're saying, host load-balancing is always needed,
but if you're talking about the whole directed yield thing, then yes,
paravirt spinlocks will take care of that.