Re: [RFC PATCH 2/3] sched: add yield_to function

[Rik van Riel]

On 12/10/2010 03:39 AM, Srivatsa Vaddagiri wrote:
> On Thu, Dec 09, 2010 at 11:34:46PM -0500, Rik van Riel wrote:
> > On 12/03/2010 09:06 AM, Srivatsa Vaddagiri wrote:
> > > On Fri, Dec 03, 2010 at 03:03:30PM +0100, Peter Zijlstra wrote:
> > > > No, because they do receive service (they spend some time spinning
> > > > before being interrupted), so the respective vruntimes will increase, at
> > > > some point they'll pass B0 and it'll get scheduled.
> > >
> > > Is that sufficient to ensure that B0 receives its fair share (1/3 cpu in this
> > > case)?
> >
> > I have a rough idea for a simpler way to ensure
> > fairness.
> >
> > At yield_to time, we could track in the runqueue
> > structure that a task received CPU time (and on
> > the other runqueue that a task donated CPU time).
> >
> > The balancer can count time-given-to CPUs as
> > busier, and donated-time CPUs as less busy,
> > moving tasks away in the unlikely event that
> > the same task gets keeping CPU time given to
> > it.
>
> I think just capping donation (either on send side or receive side) may be more
> simpler here than to mess with load balancer logic.

Do you have any ideas on how to implement this in a simple
enough way that it may be acceptable upstream? :)

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