On 01/17/2014 03:26 PM, Peter Zijlstra wrote:
On Fri, Jan 17, 2014 at 10:04:04AM +0100, Daniel Lezcano wrote:
@@ -2679,11 +2715,8 @@ need_resched:
pre_schedule(rq, prev);
- if (unlikely(!rq->nr_running))
- rq->idle_stamp = idle_balance(rq) ? 0 : rq_clock(rq);
-
put_prev_task(rq, prev);
- next = pick_next_task(rq);
+ next = pick_next_task_or_idle(rq);
clear_tsk_need_resched(prev);
clear_preempt_need_resched();
rq->skip_clock_update = 0;
I have vague memories that we need to have idle_balance() before
put_prev_task(), but I can't recollect why this would be so.
That said, if I resurrect these patches:
https://lkml.org/lkml/2012/6/14/271
I suppose we could write something like:
struct task_struct *pick_next_task(struct rq *rq, struct task_struct *prev)
{
const struct sched_class *class;
struct task_struct *p;
again:
if (likely(rq->nr_running)) {
if (likely(rq->nr_running == rq->cfs.h_nr_running))
return fair_sched_class.pick_next_task(rq, prev);
for_each_class(class) {
p = class->pick_next_task(rq, prev);
if (p)
return p;
}
}
if (idle_balance(rq))
goto again;
rq->idle_stamp = rq_clock(rq);
return idle_sched_class.pick_next_task(rq, prev);
}
Which keeps idle_balance() before put_prev_task(), and by using
idle_sched_clas.pick_next_task() doesn't rape the idle class interface
like you did :-)
But put_prev_task is called before pick_next_task, so idle_balance() is
called after now, no ?
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