On Wed, 29 Jun 2016 20:07:43 +0100
Juri Lelli <juri.le...@arm.com> wrote:
> ---
> kernel/sched/deadline.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index fcb7f0217ff4..2000ad2294d5 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -346,11 +346,12 @@ static void check_preempt_curr_dl(struct rq *rq, struct
> task_struct *p,
> * one, and to (try to!) reconcile itself with its own scheduling
> * parameters.
> */
> -static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
> - struct sched_dl_entity *pi_se)
> +static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
> {
> struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
> struct rq *rq = rq_of_dl_rq(dl_rq);
> + struct task_struct *pi_task = rt_mutex_get_top_task(dl_task_of(dl_se));
> + struct sched_dl_entity *pi_se = dl_se;
>
> WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
>
> @@ -363,6 +364,13 @@ static inline void setup_new_dl_entity(struct
> sched_dl_entity *dl_se,
> return;
>
> /*
> + * Use the scheduling parameters of the top pi-waiter task,
> + * if we have one from which we can inherit a deadline.
> + */
> + if (pi_task && dl_se->dl_boosted && dl_prio(pi_task->normal_prio))
> + pi_se = &pi_task->dl;
> +
OK, I'm micro-optimizing now, but hey, isn't this a fast path?
What about changing the above to:
struct task_struct *pi_task;
[...]
if (dl_se->dl_boosted && dl_prio(pi_task->normal_prio &&
(pi_task = rt_mutex_get_top_task(dl_task_of(dl_se)))
pe_se = &pi_task->dl;
This way we don't need to do any work of looking at
rt_mutex_get_top_task() for the normal case.
-- Steve
> + /*
> * We use the regular wall clock time to set deadlines in the
> * future; in fact, we must consider execution overheads (time
> * spent on hardirq context, etc.).
> @@ -1721,7 +1729,7 @@ static void switched_from_dl(struct rq *rq, struct
> task_struct *p)
> static void switched_to_dl(struct rq *rq, struct task_struct *p)
> {
> if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> - setup_new_dl_entity(&p->dl, &p->dl);
> + setup_new_dl_entity(&p->dl);
>
> if (task_on_rq_queued(p) && rq->curr != p) {
> #ifdef CONFIG_SMP
