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sched/deadline: Fix the update of the total -deadline utilization

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Now that the inactive timer can be armed to fire at the 0-lag time,
it is possible to use inactive_task_timer() to update the total
-deadline utilization (dl_b->total_bw) at the correct time, fixing
dl_overflow() and __setparam_dl().

Tested-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Luca Abeni <luca.abeni@santannapisa.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/1495138417-6203-4-git-send-email-luca.abeni@santannapisa.it
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Luca Abeni 2017-05-18 22:13:30 +02:00 committed by Ingo Molnar
parent 209a0cbda7
commit 387e31300b
2 changed files with 27 additions and 39 deletions
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38
kernel/sched/core.c
View File

@ -2475,9 +2475,6 @@ static inline int dl_bw_cpus(int i)
* allocated bandwidth to reflect the new situation.
*
* This function is called while holding p's rq->lock.
*
* XXX we should delay bw change until the task's 0-lag point, see
* __setparam_dl().
*/
static int dl_overflow(struct task_struct *p, int policy,
const struct sched_attr *attr)
@ -2502,16 +2499,29 @@ static int dl_overflow(struct task_struct *p, int policy,
cpus = dl_bw_cpus(task_cpu(p));
if (dl_policy(policy) && !task_has_dl_policy(p) &&
!__dl_overflow(dl_b, cpus, 0, new_bw)) {
if (hrtimer_active(&p->dl.inactive_timer))
__dl_clear(dl_b, p->dl.dl_bw);
__dl_add(dl_b, new_bw);
err = 0;
} else if (dl_policy(policy) && task_has_dl_policy(p) &&
!__dl_overflow(dl_b, cpus, p->dl.dl_bw, new_bw)) {
/*
* XXX this is slightly incorrect: when the task
* utilization decreases, we should delay the total
* utilization change until the task's 0-lag point.
* But this would require to set the task's "inactive
* timer" when the task is not inactive.
*/
__dl_clear(dl_b, p->dl.dl_bw);
__dl_add(dl_b, new_bw);
dl_change_utilization(p, new_bw);
err = 0;
} else if (!dl_policy(policy) && task_has_dl_policy(p)) {
__dl_clear(dl_b, p->dl.dl_bw);
/*
* Do not decrease the total deadline utilization here,
* switched_from_dl() will take care to do it at the correct
* (0-lag) time.
*/
err = 0;
}
raw_spin_unlock(&dl_b->lock);
@ -4020,26 +4030,6 @@ __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
dl_se->flags = attr->sched_flags;
dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
/*
* Changing the parameters of a task is 'tricky' and we're not doing
* the correct thing -- also see task_dead_dl() and switched_from_dl().
*
* What we SHOULD do is delay the bandwidth release until the 0-lag
* point. This would include retaining the task_struct until that time
* and change dl_overflow() to not immediately decrement the current
* amount.
*
* Instead we retain the current runtime/deadline and let the new
* parameters take effect after the current reservation period lapses.
* This is safe (albeit pessimistic) because the 0-lag point is always
* before the current scheduling deadline.
*
* We can still have temporary overloads because we do not delay the
* change in bandwidth until that time; so admission control is
* not on the safe side. It does however guarantee tasks will never
* consume more than promised.
*/
}
/*

28
kernel/sched/deadline.c
View File

@ -175,8 +175,14 @@ static void task_non_contending(struct task_struct *p)
if (zerolag_time < 0) {
if (dl_task(p))
sub_running_bw(dl_se->dl_bw, dl_rq);
if (!dl_task(p) || p->state == TASK_DEAD)
if (!dl_task(p) || p->state == TASK_DEAD) {
struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
raw_spin_lock(&dl_b->lock);
__dl_clear(dl_b, p->dl.dl_bw);
__dl_clear_params(p);
raw_spin_unlock(&dl_b->lock);
}
return;
}
@ -1004,10 +1010,16 @@ static enum hrtimer_restart inactive_task_timer(struct hrtimer *timer)
rq = task_rq_lock(p, &rf);
if (!dl_task(p) || p->state == TASK_DEAD) {
struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
if (p->state == TASK_DEAD && dl_se->dl_non_contending) {
sub_running_bw(p->dl.dl_bw, dl_rq_of_se(&p->dl));
dl_se->dl_non_contending = 0;
}
raw_spin_lock(&dl_b->lock);
__dl_clear(dl_b, p->dl.dl_bw);
raw_spin_unlock(&dl_b->lock);
__dl_clear_params(p);
goto unlock;
@ -1534,19 +1546,6 @@ static void task_fork_dl(struct task_struct *p)
*/
}
static void task_dead_dl(struct task_struct *p)
{
struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
/*
* Since we are TASK_DEAD we won't slip out of the domain!
*/
raw_spin_lock_irq(&dl_b->lock);
/* XXX we should retain the bw until 0-lag */
dl_b->total_bw -= p->dl.dl_bw;
raw_spin_unlock_irq(&dl_b->lock);
}
static void set_curr_task_dl(struct rq *rq)
{
struct task_struct *p = rq->curr;
@ -2141,7 +2140,6 @@ const struct sched_class dl_sched_class = {
.set_curr_task = set_curr_task_dl,
.task_tick = task_tick_dl,
.task_fork = task_fork_dl,
.task_dead = task_dead_dl,
.prio_changed = prio_changed_dl,
.switched_from = switched_from_dl,