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sched/fair: Re-organize dequeue_task_fair()

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Working towards delaying dequeue, notably also inside the hierachy,
rework dequeue_task_fair() such that it can 'resume' an interrupted
hierarchy walk.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105028.977256873@infradead.org
This commit is contained in:
Peter Zijlstra 2024-04-03 09:50:41 +02:00
parent 863ccdbb91
commit fab4a808ba
1 changed files with 41 additions and 21 deletions
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62
kernel/sched/fair.c
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@ -6861,34 +6861,43 @@ enqueue_throttle:
static void set_next_buddy(struct sched_entity *se);
/*
* The dequeue_task method is called before nr_running is
* decreased. We remove the task from the rbtree and
* update the fair scheduling stats:
* Basically dequeue_task_fair(), except it can deal with dequeue_entity()
* failing half-way through and resume the dequeue later.
*
* Returns:
* -1 - dequeue delayed
* 0 - dequeue throttled
* 1 - dequeue complete
*/
static bool dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags)
{
struct cfs_rq *cfs_rq;
struct sched_entity *se = &p->se;
int task_sleep = flags & DEQUEUE_SLEEP;
int idle_h_nr_running = task_has_idle_policy(p);
bool was_sched_idle = sched_idle_rq(rq);
int rq_h_nr_running = rq->cfs.h_nr_running;
bool task_sleep = flags & DEQUEUE_SLEEP;
struct task_struct *p = NULL;
int idle_h_nr_running = 0;
int h_nr_running = 0;
struct cfs_rq *cfs_rq;
util_est_dequeue(&rq->cfs, p);
if (entity_is_task(se)) {
p = task_of(se);
h_nr_running = 1;
idle_h_nr_running = task_has_idle_policy(p);
}
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
dequeue_entity(cfs_rq, se, flags);
cfs_rq->h_nr_running--;
cfs_rq->h_nr_running -= h_nr_running;
cfs_rq->idle_h_nr_running -= idle_h_nr_running;
if (cfs_rq_is_idle(cfs_rq))
idle_h_nr_running = 1;
idle_h_nr_running = h_nr_running;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(cfs_rq))
goto dequeue_throttle;
return 0;
/* Don't dequeue parent if it has other entities besides us */
if (cfs_rq->load.weight) {
@ -6912,20 +6921,18 @@ static bool dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
se_update_runnable(se);
update_cfs_group(se);
cfs_rq->h_nr_running--;
cfs_rq->h_nr_running -= h_nr_running;
cfs_rq->idle_h_nr_running -= idle_h_nr_running;
if (cfs_rq_is_idle(cfs_rq))
idle_h_nr_running = 1;
idle_h_nr_running = h_nr_running;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(cfs_rq))
goto dequeue_throttle;
return 0;
}
/* At this point se is NULL and we are at root level*/
sub_nr_running(rq, 1);
sub_nr_running(rq, h_nr_running);
if (rq_h_nr_running && !rq->cfs.h_nr_running)
dl_server_stop(&rq->fair_server);
@ -6934,10 +6941,23 @@ static bool dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
rq->next_balance = jiffies;
dequeue_throttle:
util_est_update(&rq->cfs, p, task_sleep);
hrtick_update(rq);
return 1;
}
/*
* The dequeue_task method is called before nr_running is
* decreased. We remove the task from the rbtree and
* update the fair scheduling stats:
*/
static bool dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
{
util_est_dequeue(&rq->cfs, p);
if (dequeue_entities(rq, &p->se, flags) < 0)
return false;
util_est_update(&rq->cfs, p, flags & DEQUEUE_SLEEP);
hrtick_update(rq);
return true;
}