linux-kernel - [PATCH v6.6 3/4] sched/fair: Small cleanup to update_newidle

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Message-Id: <20251203112255.1738272-4-ajay.kaher@broadcom.com>
Date: Wed,  3 Dec 2025 11:22:54 +0000
From: Ajay Kaher <ajay.kaher@...adcom.com>
To: stable@...r.kernel.org,
	gregkh@...uxfoundation.org
Cc: mingo@...hat.com,
	peterz@...radead.org,
	juri.lelli@...hat.com,
	vincent.guittot@...aro.org,
	dietmar.eggemann@....com,
	rostedt@...dmis.org,
	bsegall@...gle.com,
	mgorman@...e.de,
	vschneid@...hat.com,
	linux-kernel@...r.kernel.org,
	ajay.kaher@...adcom.com,
	alexey.makhalov@...adcom.com,
	yin.ding@...adcom.com,
	tapas.kundu@...adcom.com,
	Chris Mason <clm@...a.com>
Subject: [PATCH v6.6 3/4] sched/fair: Small cleanup to update_newidle_cost()

From: Peter Zijlstra <peterz@...radead.org>

commit 08d473dd8718e4a4d698b1113a14a40ad64a909b upstream.

Simplify code by adding a few variables.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@....com>
Tested-by: Chris Mason <clm@...a.com>
Link: https://patch.msgid.link/20251107161739.655208666@infradead.org
[ Ajay: Modified to apply on v6.6 ]
Signed-off-by: Ajay Kaher <ajay.kaher@...adcom.com>
---
 kernel/sched/fair.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e47bf8d6c..f93a6a12e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11706,22 +11706,25 @@ void update_max_interval(void)
 
 static inline bool update_newidle_cost(struct sched_domain *sd, u64 cost)
 {
+	unsigned long next_decay = sd->last_decay_max_lb_cost + HZ;
+	unsigned long now = jiffies;
+
 	if (cost > sd->max_newidle_lb_cost) {
 		/*
 		 * Track max cost of a domain to make sure to not delay the
 		 * next wakeup on the CPU.
 		 */
 		sd->max_newidle_lb_cost = cost;
-		sd->last_decay_max_lb_cost = jiffies;
-	} else if (time_after(jiffies, sd->last_decay_max_lb_cost + HZ)) {
+		sd->last_decay_max_lb_cost = now;
+
+	} else if (time_after(now, next_decay)) {
 		/*
 		 * Decay the newidle max times by ~1% per second to ensure that
 		 * it is not outdated and the current max cost is actually
 		 * shorter.
 		 */
 		sd->max_newidle_lb_cost = (sd->max_newidle_lb_cost * 253) / 256;
-		sd->last_decay_max_lb_cost = jiffies;
-
+		sd->last_decay_max_lb_cost = now;
 		return true;
 	}
 
-- 
2.40.4