From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH] qemu-kvm: response to SIGUSR1 to start/stop a VCPU (v2)
Date: Wed, 01 Dec 2010 20:47:35 +0100
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Cc: Chris Wright <chrisw@sous-sol.org>, vatsa@linux.vnet.ibm.com,
	Avi Kivity <avi@redhat.com>,
	Anthony Liguori <aliguori@linux.vnet.ibm.com>,
	qemu-devel@nongnu.org, kvm@vger.kernel.org,
	Ingo Molnar <mingo@elte.hu>, Mike Galbraith <efault@gmx.de>
To: Rik van Riel <riel@redhat.com>
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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.