linux-kernel - [PATCH 4/5] sched/fair: Remove NEXT

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Message-Id: <20240407084319.1462211-5-mingo@kernel.org>
Date: Sun,  7 Apr 2024 10:43:18 +0200
From: Ingo Molnar <mingo@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Shrikanth Hegde <sshegde@...ux.ibm.com>,
	Valentin Schneider <vschneid@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH 4/5] sched/fair: Remove NEXT_BUDDY

It has been turned off in 2009 and hasn't been enabled since,
15 years ought to be enough to remove it.

Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/fair.c     | 11 -----------
 kernel/sched/features.h |  7 -------
 2 files changed, 18 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0197ba78b89c..93ea653065f5 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1901,13 +1901,6 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 static struct sched_entity *
 pick_next_entity(struct cfs_rq *cfs_rq)
 {
-	/*
-	 * Enabling NEXT_BUDDY will affect latency but not fairness.
-	 */
-	if (sched_feat(NEXT_BUDDY) &&
-	    cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next))
-		return cfs_rq->next;
-
 	return pick_eevdf(cfs_rq);
 }
 
@@ -4671,10 +4664,6 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
 	if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
 		return;
 
-	if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK)) {
-		set_next_buddy(pse);
-	}
-
 	/*
 	 * We can come here with TIF_NEED_RESCHED already set from new task
 	 * wake up path.
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index 143f55df890b..f0df03fe24d8 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -8,13 +8,6 @@ SCHED_FEAT(PLACE_LAG, true)
 SCHED_FEAT(PLACE_DEADLINE_INITIAL, true)
 SCHED_FEAT(RUN_TO_PARITY, true)
 
-/*
- * Prefer to schedule the task we woke last (assuming it failed
- * wakeup-preemption), since its likely going to consume data we
- * touched, increases cache locality.
- */
-SCHED_FEAT(NEXT_BUDDY, false)
-
 /*
  * Consider buddies to be cache hot, decreases the likeliness of a
  * cache buddy being migrated away, increases cache locality.
-- 
2.40.1