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sched/fair: Reorder enqueue/dequeue_task_fair path

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The walk through the cgroup hierarchy during the enqueue/dequeue of a task
is split in 2 distinct parts for throttled cfs_rq without any added value
but making code less readable.

Change the code ordering such that everything related to a cfs_rq
(throttled or not) will be done in the same loop.

In addition, the same steps ordering is used when updating a cfs_rq:

 - update_load_avg
 - update_cfs_group
 - update *h_nr_running

This reordering enables the use of h_nr_running in PELT algorithm.

No functional and performance changes are expected and have been noticed
during tests.

Signed-off-by: Vincent Guittot <[email protected]>
Signed-off-by: Mel Gorman <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Reviewed-by: "Dietmar Eggemann <[email protected]>"
Acked-by: Peter Zijlstra <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Valentin Schneider <[email protected]>
Cc: Phil Auld <[email protected]>
Cc: Hillf Danton <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
This commit is contained in:
Vincent Guittot authored and Ingo Molnar committed 2020-02-24 11:36:34 +01:00
1 parent b2b2042b20
commit 6d4d22468d
1 file changed
+20 -22
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kernel/sched/fair.c
+20 -22
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@@ -5260,32 +5260,31 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
cfs_rq = cfs_rq_of(se);
enqueue_entity(cfs_rq, se, flags);
/*
* end evaluation on encountering a throttled cfs_rq
*
* note: in the case of encountering a throttled cfs_rq we will
* post the final h_nr_running increment below.
*/
if (cfs_rq_throttled(cfs_rq))
break;
cfs_rq->h_nr_running++;
cfs_rq->idle_h_nr_running += idle_h_nr_running;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(cfs_rq))
goto enqueue_throttle;
flags = ENQUEUE_WAKEUP;
}
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
cfs_rq->h_nr_running++;
cfs_rq->idle_h_nr_running += idle_h_nr_running;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(cfs_rq))
break;
goto enqueue_throttle;
update_load_avg(cfs_rq, se, UPDATE_TG);
update_cfs_group(se);
cfs_rq->h_nr_running++;
cfs_rq->idle_h_nr_running += idle_h_nr_running;
}
enqueue_throttle:
if (!se) {
add_nr_running(rq, 1);
/*
@@ -5346,17 +5345,13 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
cfs_rq = cfs_rq_of(se);
dequeue_entity(cfs_rq, se, flags);
/*
* end evaluation on encountering a throttled cfs_rq
*
* note: in the case of encountering a throttled cfs_rq we will
* post the final h_nr_running decrement below.
*/
if (cfs_rq_throttled(cfs_rq))
break;
cfs_rq->h_nr_running--;
cfs_rq->idle_h_nr_running -= idle_h_nr_running;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(cfs_rq))
goto dequeue_throttle;
/* Don't dequeue parent if it has other entities besides us */
if (cfs_rq->load.weight) {
/* Avoid re-evaluating load for this entity: */
@@ -5374,16 +5369,19 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
cfs_rq->h_nr_running--;
cfs_rq->idle_h_nr_running -= idle_h_nr_running;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(cfs_rq))
break;
goto dequeue_throttle;
update_load_avg(cfs_rq, se, UPDATE_TG);
update_cfs_group(se);
cfs_rq->h_nr_running--;
cfs_rq->idle_h_nr_running -= idle_h_nr_running;
}
dequeue_throttle:
if (!se)
sub_nr_running(rq, 1);