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sched/fair: Unify pick_{,next_}_task_fair()

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Implement pick_next_task_fair() in terms of pick_task_fair() to
de-duplicate the pick loop.

More importantly, this makes all the pick loops use the
state-invariant form, which is useful to introduce further re-try
conditions in later patches.

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/20240727105028.725062368@infradead.org
This commit is contained in:
Peter Zijlstra 2024-04-03 09:50:16 +02:00
parent c97f54fe6d
commit 3b3dd89b8b
1 changed files with 8 additions and 52 deletions
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60
kernel/sched/fair.c
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@ -8451,7 +8451,6 @@ preempt:
resched_curr(rq);
}
#ifdef CONFIG_SMP
static struct task_struct *pick_task_fair(struct rq *rq)
{
struct sched_entity *se;
@ -8463,7 +8462,7 @@ again:
return NULL;
do {
/* When we pick for a remote RQ, we'll not have done put_prev_entity() */
/* Might not have done put_prev_entity() */
if (cfs_rq->curr && cfs_rq->curr->on_rq)
update_curr(cfs_rq);
@ -8484,19 +8483,19 @@ again:
return task_of(se);
}
#endif
struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
struct cfs_rq *cfs_rq = &rq->cfs;
struct sched_entity *se;
struct task_struct *p;
int new_tasks;
again:
if (!sched_fair_runnable(rq))
p = pick_task_fair(rq);
if (!p)
goto idle;
se = &p->se;
#ifdef CONFIG_FAIR_GROUP_SCHED
if (!prev || prev->sched_class != &fair_sched_class)
@ -8508,52 +8507,14 @@ again:
*
* Therefore attempt to avoid putting and setting the entire cgroup
* hierarchy, only change the part that actually changes.
*/
do {
struct sched_entity *curr = cfs_rq->curr;
/*
* Since we got here without doing put_prev_entity() we also
* have to consider cfs_rq->curr. If it is still a runnable
* entity, update_curr() will update its vruntime, otherwise
* forget we've ever seen it.
*/
if (curr) {
if (curr->on_rq)
update_curr(cfs_rq);
else
curr = NULL;
/*
* This call to check_cfs_rq_runtime() will do the
* throttle and dequeue its entity in the parent(s).
* Therefore the nr_running test will indeed
* be correct.
*/
if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
cfs_rq = &rq->cfs;
if (!cfs_rq->nr_running)
goto idle;
goto simple;
}
}
se = pick_next_entity(cfs_rq);
cfs_rq = group_cfs_rq(se);
} while (cfs_rq);
p = task_of(se);
/*
*
* Since we haven't yet done put_prev_entity and if the selected task
* is a different task than we started out with, try and touch the
* least amount of cfs_rqs.
*/
if (prev != p) {
struct sched_entity *pse = &prev->se;
struct cfs_rq *cfs_rq;
while (!(cfs_rq = is_same_group(se, pse))) {
int se_depth = se->depth;
@ -8579,13 +8540,8 @@ simple:
if (prev)
put_prev_task(rq, prev);
do {
se = pick_next_entity(cfs_rq);
set_next_entity(cfs_rq, se);
cfs_rq = group_cfs_rq(se);
} while (cfs_rq);
p = task_of(se);
for_each_sched_entity(se)
set_next_entity(cfs_rq_of(se), se);
done: __maybe_unused;
#ifdef CONFIG_SMP