linux-kernel - [PATCH 1/3] sched/fair: Set sched_entity::depth only when parent has changed

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Message-ID: <148767900991.5212.16341443539923627997.stgit@localhost.localdomain>
Date:   Tue, 21 Feb 2017 15:10:22 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     <peterz@...radead.org>, <mingo@...hat.com>,
        <linux-kernel@...r.kernel.org>, <ktkhai@...tuozzo.com>
Subject: [PATCH 1/3] sched/fair: Set sched_entity::depth only when parent
 has changed

Currently we set depth in two places, and this confuses a reader.
Task's depth depends on parent's depth and it may change only if
parent has changed. So, set it in set_task_rq(), where parent is set.

(cfs_rq's depth is set in init_tg_cfs_entry() and it's static, so
 this change don't touch them).

Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
---
 kernel/sched/fair.c  |   11 -----------
 kernel/sched/sched.h |    1 +
 2 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3e88b35ac157..33b46ca301f0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9102,14 +9102,6 @@ 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(se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
 	attach_entity_load_avg(cfs_rq, se);
@@ -9204,10 +9196,7 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
 #ifdef CONFIG_FAIR_GROUP_SCHED
 static void task_set_group_fair(struct task_struct *p)
 {
-	struct sched_entity *se = &p->se;
-
 	set_task_rq(p, task_cpu(p));
-	se->depth = se->parent ? se->parent->depth + 1 : 0;
 }
 
 static void task_move_group_fair(struct task_struct *p)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 207fc1f4c764..4a9313f0b5c8 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1123,6 +1123,7 @@ 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 = p->se.parent ? p->se.parent->depth + 1 : 0;
 #endif
 
 #ifdef CONFIG_RT_GROUP_SCHED