Re: [PATCH 06/16] sched: SCHED_DEADLINE push and pull logic

[Juri Lelli]

On 04/11/2012 06:14 PM, Steven Rostedt wrote:
> On Fri, 2012-04-06 at 09:14 +0200, Juri Lelli wrote:
>
> > +static int latest_cpu_find(struct cpumask *span,
> > +			   struct task_struct *task,
> > +			   struct cpumask *later_mask)
> >   {
> > +	const struct sched_dl_entity *dl_se =&task->dl;
> > +	int cpu, found = -1, best = 0;
> > +	u64 max_dl = 0;
> > +
> > +	for_each_cpu(cpu, span) {
> > +		struct rq *rq = cpu_rq(cpu);
> > +		struct dl_rq *dl_rq =&rq->dl;
> > +
> > +		if (cpumask_test_cpu(cpu,&task->cpus_allowed)&&
> > +		    (!dl_rq->dl_nr_running || dl_time_before(dl_se->deadline,
> > +		     dl_rq->earliest_dl.curr))) {
> > +			if (later_mask)
> > +				cpumask_set_cpu(cpu, later_mask);
> > +			if (!best&&  !dl_rq->dl_nr_running) {
>
> I hate to say this (and I also have yet to look at the patches after
> this) but we should really take into account the RT tasks. It would suck
> to preempt a normal RT task when a non RT task is running on another
> CPU.

Well, this changes in 15/16, but your point remains, and I see it :-).
We are currently reworking the push/pull mechanism (15/16 will most probably
change as well) to speed it up. I agree that it would be nice to take into
accont RT tasks as well, so we'll surely think about it.
  
> > +				best = 1;
> > +				found = cpu;
> > +			} else if (!best&&
> > +				   dl_time_before(max_dl,
> > +						  dl_rq->earliest_dl.curr)) {
> > +				max_dl = dl_rq->earliest_dl.curr;
> > +				found = cpu;
> > +			}
> > +		} else if (later_mask)
> > +			cpumask_clear_cpu(cpu, later_mask);
> > +	}
> > +
> > +	return found;
> > +}

Thanks,

- Juri
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