Re: [PATCH 13/32] nohz: Adaptive tick stop and restart on nohz cpuset

Frederic Weisbecker
2011-08-29T18:02:31Z

On Mon, Aug 29, 2011 at 05:28:09PM +0200, Peter Zijlstra wrote:
> On Mon, 2011-08-15 at 17:52 +0200, Frederic Weisbecker wrote:
> > +bool cpuset_nohz_can_stop_tick(void)
> > +{
> > + struct rq *rq;
> > +
> > + rq = this_rq();
> > +
> > + /* More than one running task need preemption */
> > + if (rq->nr_running > 1)
> > + return false;
> > +
> > + return true;
> > +}
>
> int sched_needs_cpu(int cpu), seems the right name, matches the existing
> {rcu,printk,arch}_needs_cpu() functions.

tick_nohz_stop_sched_tick() already handles that by keeping a periodic
behaviour if one of these conditions are met.

It has also the upside to restore the periodic behaviour if needed
from irq return if the tick was stopped.