[tip: sched/core] sched/fair: Maintain task se depth in set_task_rq()

From: tip-bot2 for Chengming Zhou
Date: Tue Aug 23 2022 - 07:42:22 EST


The following commit has been merged into the sched/core branch of tip:

Commit-ID: 78b6b15770618efb60d84e2d605f6b93dc94051b
Gitweb: https://git.kernel.org/tip/78b6b15770618efb60d84e2d605f6b93dc94051b
Author: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
AuthorDate: Thu, 18 Aug 2022 20:47:57 +08:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 23 Aug 2022 11:01:17 +02:00

sched/fair: Maintain task se depth in set_task_rq()

Previously we only maintain task se depth in task_move_group_fair(),
if a !fair task change task group, its se depth will not be updated,
so commit eb7a59b2c888 ("sched/fair: Reset se-depth when task switched to FAIR")
fix the problem by updating se depth in switched_to_fair() too.

Then commit daa59407b558 ("sched/fair: Unify switched_{from,to}_fair()
and task_move_group_fair()") unified these two functions, moved se.depth
setting to attach_task_cfs_rq(), which further into attach_entity_cfs_rq()
with commit df217913e72e ("sched/fair: Factorize attach/detach entity").

This patch move task se depth maintenance from attach_entity_cfs_rq()
to set_task_rq(), which will be called when CPU/cgroup change, so its
depth will always be correct.

This patch is preparation for the next patch.

Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220818124805.601-2-zhouchengming@xxxxxxxxxxxxx
---
kernel/sched/fair.c | 8 --------
kernel/sched/sched.h | 1 +
2 files changed, 1 insertion(+), 8 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index da38865..a3b0f8b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11562,14 +11562,6 @@ static void attach_entity_cfs_rq(struct sched_entity *se)
{
struct cfs_rq *cfs_rq = cfs_rq_of(se);

-#ifdef CONFIG_FAIR_GROUP_SCHED
- /*
- * Since the real-depth could have been changed (only FAIR
- * class maintain depth value), reset depth properly.
- */
- se->depth = se->parent ? se->parent->depth + 1 : 0;
-#endif
-
/* Synchronize entity with its cfs_rq */
update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
attach_entity_load_avg(cfs_rq, se);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 3ccd35c..4c48221 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1930,6 +1930,7 @@ static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
set_task_rq_fair(&p->se, p->se.cfs_rq, tg->cfs_rq[cpu]);
p->se.cfs_rq = tg->cfs_rq[cpu];
p->se.parent = tg->se[cpu];
+ p->se.depth = tg->se[cpu] ? tg->se[cpu]->depth + 1 : 0;
#endif

#ifdef CONFIG_RT_GROUP_SCHED