linux-kernel - [PATCH v6 1/9] sched/fair: maintain task se depth in set_task

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Message-Id: <20220818124805.601-2-zhouchengming@bytedance.com>
Date:   Thu, 18 Aug 2022 20:47:57 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     vincent.guittot@...aro.org, dietmar.eggemann@....com,
        mingo@...hat.com, peterz@...radead.org, rostedt@...dmis.org,
        bsegall@...gle.com, vschneid@...hat.com
Cc:     linux-kernel@...r.kernel.org, tj@...nel.org,
        Chengming Zhou <zhouchengming@...edance.com>
Subject: [PATCH v6 1/9] 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@...edance.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>
Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
---
 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 a71d6686149b..c5ee08b187ec 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11726,14 +11726,6 @@ 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 ddcfc7837595..628ffa974123 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1932,6 +1932,7 @@ 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
-- 
2.37.2