Re: Very high CPU load when idle with 3.0-rc1

Paul E. McKenney
2011-05-30T21:28:40Z

On Mon, May 30, 2011 at 07:19:49PM +0200, Peter Zijlstra wrote:
> On Mon, 2011-05-30 at 09:23 -0700, Paul E. McKenney wrote:
> > sp.sched_priority = RCU_KTHREAD_PRIO;
> > sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
>
> Why are those things RT tasks anyway? The old ksoftirq runs as a regular
> task. And once you start boosting things you can boost this into FIFO as
> well...
>
> just wondering..

Because priority boosting doesn't help unless the callbacks also run
RT priority.

I could make it so that they ran as normal tasks if !RCU_BOOST, but
they would still need to run as RT tasks for RCU_BOOST. I figured
running them the same way in both cases would be simpler.

Thanx, Paul