Messages in this thread | | | Date | Wed, 22 Oct 2014 10:43:41 +0100 | From | Juri Lelli <> | Subject | Re: [RFC] sched/dl: Fix preemption checks |
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Hi Kirill,
On 21/10/14 17:35, Kirill Tkhai wrote: > > 1)switched_to_dl() check is wrong. We reschedule only > if rq->curr is deadline task, and we do not reschedule > if it's a lower priority task. But we must always > preempt a task of other classes. > > 2)dl_task_timer(): > Policy does not change in case of priority inheritance. > rt_mutex_setprio() changes prio, while policy remains old. > > So we lose some balancing logic in dl_task_timer() and > switched_to_dl() when we check policy instead of priority. > Boosted task may be rq->curr. > > (I didn't change switched_from_dl() because no check is > necessary there at all). > > I've looked at this place(switched_to_dl) several times > and even fixed this function, but found just now... > I suppose some performance tests may work better after this. > > Completely untested, just RFC. > > Juri how about this? >
I'll have to give it a spin, but it looks good.
Thanks,
- Juri
> Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> > --- > kernel/sched/deadline.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 256e577..937a875 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -532,7 +532,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) > dl_se->dl_yielded = 0; > if (task_on_rq_queued(p)) { > enqueue_task_dl(rq, p, ENQUEUE_REPLENISH); > - if (task_has_dl_policy(rq->curr)) > + if (dl_task(rq->curr)) > check_preempt_curr_dl(rq, p, 0); > else > resched_curr(rq); > @@ -1607,8 +1607,12 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p) > /* Only reschedule if pushing failed */ > check_resched = 0; > #endif /* CONFIG_SMP */ > - if (check_resched && task_has_dl_policy(rq->curr)) > - check_preempt_curr_dl(rq, p, 0); > + if (check_resched) { > + if (dl_task(rq->curr)) > + check_preempt_curr_dl(rq, p, 0); > + else > + resched_curr(rq); > + } > } > } > > > > > >
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