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sched/deadline: Move bandwidth accounting into {en,de}queue_dl_entity
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In preparation of introducing !task sched_dl_entity; move the
bandwidth accounting into {en.de}queue_dl_entity().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/a86dccbbe44e021b8771627e1dae01a69b73466d.1699095159.git.bristot@kernel.org
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Peter Zijlstra committed Nov 15, 2023
1 parent 9e07d45 commit 2f7a0f5
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Showing 2 changed files with 78 additions and 58 deletions.
130 changes: 72 additions & 58 deletions kernel/sched/deadline.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -391,12 +391,12 @@ static void __dl_clear_params(struct sched_dl_entity *dl_se);
* up, and checks if the task is still in the "ACTIVE non contending"
* state or not (in the second case, it updates running_bw).
*/
static void task_non_contending(struct task_struct *p)
static void task_non_contending(struct sched_dl_entity *dl_se)
{
struct sched_dl_entity *dl_se = &p->dl;
struct hrtimer *timer = &dl_se->inactive_timer;
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);
struct task_struct *p = dl_task_of(dl_se);
s64 zerolag_time;

/*
Expand Down Expand Up @@ -428,13 +428,14 @@ static void task_non_contending(struct task_struct *p)
if ((zerolag_time < 0) || hrtimer_active(&dl_se->inactive_timer)) {
if (dl_task(p))
sub_running_bw(dl_se, dl_rq);

if (!dl_task(p) || READ_ONCE(p->__state) == TASK_DEAD) {
struct dl_bw *dl_b = dl_bw_of(task_cpu(p));

if (READ_ONCE(p->__state) == TASK_DEAD)
sub_rq_bw(&p->dl, &rq->dl);
sub_rq_bw(dl_se, &rq->dl);
raw_spin_lock(&dl_b->lock);
__dl_sub(dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
__dl_sub(dl_b, dl_se->dl_bw, dl_bw_cpus(task_cpu(p)));
raw_spin_unlock(&dl_b->lock);
__dl_clear_params(dl_se);
}
Expand Down Expand Up @@ -1601,6 +1602,41 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)

update_stats_enqueue_dl(dl_rq_of_se(dl_se), dl_se, flags);

/*
* Check if a constrained deadline task was activated
* after the deadline but before the next period.
* If that is the case, the task will be throttled and
* the replenishment timer will be set to the next period.
*/
if (!dl_se->dl_throttled && !dl_is_implicit(dl_se))
dl_check_constrained_dl(dl_se);

if (flags & (ENQUEUE_RESTORE|ENQUEUE_MIGRATING)) {
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);

add_rq_bw(dl_se, dl_rq);
add_running_bw(dl_se, dl_rq);
}

/*
* If p is throttled, we do not enqueue it. In fact, if it exhausted
* its budget it needs a replenishment and, since it now is on
* its rq, the bandwidth timer callback (which clearly has not
* run yet) will take care of this.
* However, the active utilization does not depend on the fact
* that the task is on the runqueue or not (but depends on the
* task's state - in GRUB parlance, "inactive" vs "active contending").
* In other words, even if a task is throttled its utilization must
* be counted in the active utilization; hence, we need to call
* add_running_bw().
*/
if (dl_se->dl_throttled && !(flags & ENQUEUE_REPLENISH)) {
if (flags & ENQUEUE_WAKEUP)
task_contending(dl_se, flags);

return;
}

/*
* If this is a wakeup or a new instance, the scheduling
* parameters of the task might need updating. Otherwise,
Expand All @@ -1620,9 +1656,28 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
__enqueue_dl_entity(dl_se);
}

static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
static void dequeue_dl_entity(struct sched_dl_entity *dl_se, int flags)
{
__dequeue_dl_entity(dl_se);

if (flags & (DEQUEUE_SAVE|DEQUEUE_MIGRATING)) {
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);

sub_running_bw(dl_se, dl_rq);
sub_rq_bw(dl_se, dl_rq);
}

/*
* This check allows to start the inactive timer (or to immediately
* decrease the active utilization, if needed) in two cases:
* when the task blocks and when it is terminating
* (p->state == TASK_DEAD). We can handle the two cases in the same
* way, because from GRUB's point of view the same thing is happening
* (the task moves from "active contending" to "active non contending"
* or "inactive")
*/
if (flags & DEQUEUE_SLEEP)
task_non_contending(dl_se);
}

static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
Expand Down Expand Up @@ -1667,76 +1722,35 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
return;
}

/*
* Check if a constrained deadline task was activated
* after the deadline but before the next period.
* If that is the case, the task will be throttled and
* the replenishment timer will be set to the next period.
*/
if (!p->dl.dl_throttled && !dl_is_implicit(&p->dl))
dl_check_constrained_dl(&p->dl);

if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & ENQUEUE_RESTORE) {
add_rq_bw(&p->dl, &rq->dl);
add_running_bw(&p->dl, &rq->dl);
}

/*
* If p is throttled, we do not enqueue it. In fact, if it exhausted
* its budget it needs a replenishment and, since it now is on
* its rq, the bandwidth timer callback (which clearly has not
* run yet) will take care of this.
* However, the active utilization does not depend on the fact
* that the task is on the runqueue or not (but depends on the
* task's state - in GRUB parlance, "inactive" vs "active contending").
* In other words, even if a task is throttled its utilization must
* be counted in the active utilization; hence, we need to call
* add_running_bw().
*/
if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH)) {
if (flags & ENQUEUE_WAKEUP)
task_contending(&p->dl, flags);

return;
}

check_schedstat_required();
update_stats_wait_start_dl(dl_rq_of_se(&p->dl), &p->dl);

if (p->on_rq == TASK_ON_RQ_MIGRATING)
flags |= ENQUEUE_MIGRATING;

enqueue_dl_entity(&p->dl, flags);

if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
if (!task_current(rq, p) && !p->dl.dl_throttled && p->nr_cpus_allowed > 1)
enqueue_pushable_dl_task(rq, p);
}

static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
{
update_stats_dequeue_dl(&rq->dl, &p->dl, flags);
dequeue_dl_entity(&p->dl);
dequeue_pushable_dl_task(rq, p);
dequeue_dl_entity(&p->dl, flags);

if (!p->dl.dl_throttled)
dequeue_pushable_dl_task(rq, p);
}

static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
{
update_curr_dl(rq);
__dequeue_task_dl(rq, p, flags);

if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & DEQUEUE_SAVE) {
sub_running_bw(&p->dl, &rq->dl);
sub_rq_bw(&p->dl, &rq->dl);
}
if (p->on_rq == TASK_ON_RQ_MIGRATING)
flags |= DEQUEUE_MIGRATING;

/*
* This check allows to start the inactive timer (or to immediately
* decrease the active utilization, if needed) in two cases:
* when the task blocks and when it is terminating
* (p->state == TASK_DEAD). We can handle the two cases in the same
* way, because from GRUB's point of view the same thing is happening
* (the task moves from "active contending" to "active non contending"
* or "inactive")
*/
if (flags & DEQUEUE_SLEEP)
task_non_contending(p);
__dequeue_task_dl(rq, p, flags);
}

/*
Expand Down Expand Up @@ -2551,7 +2565,7 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
* will reset the task parameters.
*/
if (task_on_rq_queued(p) && p->dl.dl_runtime)
task_non_contending(p);
task_non_contending(&p->dl);

/*
* In case a task is setscheduled out from SCHED_DEADLINE we need to
Expand Down
6 changes: 6 additions & 0 deletions kernel/sched/sched.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2177,6 +2177,10 @@ extern const u32 sched_prio_to_wmult[40];
* MOVE - paired with SAVE/RESTORE, explicitly does not preserve the location
* in the runqueue.
*
* NOCLOCK - skip the update_rq_clock() (avoids double updates)
*
* MIGRATION - p->on_rq == TASK_ON_RQ_MIGRATING (used for DEADLINE)
*
* ENQUEUE_HEAD - place at front of runqueue (tail if not specified)
* ENQUEUE_REPLENISH - CBS (replenish runtime and postpone deadline)
* ENQUEUE_MIGRATED - the task was migrated during wakeup
Expand All @@ -2187,6 +2191,7 @@ extern const u32 sched_prio_to_wmult[40];
#define DEQUEUE_SAVE 0x02 /* Matches ENQUEUE_RESTORE */
#define DEQUEUE_MOVE 0x04 /* Matches ENQUEUE_MOVE */
#define DEQUEUE_NOCLOCK 0x08 /* Matches ENQUEUE_NOCLOCK */
#define DEQUEUE_MIGRATING 0x100 /* Matches ENQUEUE_MIGRATING */

#define ENQUEUE_WAKEUP 0x01
#define ENQUEUE_RESTORE 0x02
Expand All @@ -2201,6 +2206,7 @@ extern const u32 sched_prio_to_wmult[40];
#define ENQUEUE_MIGRATED 0x00
#endif
#define ENQUEUE_INITIAL 0x80
#define ENQUEUE_MIGRATING 0x100

#define RETRY_TASK ((void *)-1UL)

Expand Down

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