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From: Peter Zijlstra <peterz@infradead.org>
To: Chris Mason <clm@meta.com>,
	Joseph Salisbury <joseph.salisbury@oracle.com>,
	Adam Li <adamli@os.amperecomputing.com>,
	Hazem Mohamed Abuelfotoh <abuehaze@amazon.com>,
	Josh Don <joshdon@google.com>
Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
	rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
	vschneid@redhat.com, linux-kernel@vger.kernel.org
Subject: [PATCH 3/4] sched/fair: Small cleanup to update_newidle_cost()
Date: Fri, 07 Nov 2025 17:06:48 +0100	[thread overview]
Message-ID: <20251107161739.655208666@infradead.org> (raw)
In-Reply-To: 20251107160645.929564468@infradead.org

Simplify code by adding a few variables.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/sched/fair.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12148,22 +12148,25 @@ 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 		 * it is not outdated and the current max cost is actually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;
 	}
 



  parent reply	other threads:[~2025-11-07 16:18 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-11-07 16:06 [PATCH 0/4] sched: The newidle balance regression Peter Zijlstra
2025-11-07 16:06 ` [PATCH 1/4] sched/fair: Revert max_newidle_lb_cost bump Peter Zijlstra
2025-11-14 12:19   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2025-11-17 16:23   ` tip-bot2 for Peter Zijlstra
2025-11-07 16:06 ` [PATCH 2/4] sched/fair: Small cleanup to sched_balance_newidle() Peter Zijlstra
2025-11-10 13:55   ` Dietmar Eggemann
2025-11-10 14:04     ` Peter Zijlstra
2025-11-12 14:37   ` Shrikanth Hegde
2025-11-12 14:42     ` Peter Zijlstra
2025-11-12 15:08       ` Peter Zijlstra
2025-11-12 15:28         ` Shrikanth Hegde
2025-11-14  9:49           ` Peter Zijlstra
2025-11-14 10:22             ` Vincent Guittot
2025-11-14 11:05               ` Peter Zijlstra
2025-11-14 13:11                 ` Vincent Guittot
2025-11-14 12:19   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2025-11-17 16:23   ` tip-bot2 for Peter Zijlstra
2025-11-07 16:06 ` Peter Zijlstra [this message]
2025-11-14 12:19   ` [tip: sched/core] sched/fair: Small cleanup to update_newidle_cost() tip-bot2 for Peter Zijlstra
2025-11-17 16:23   ` tip-bot2 for Peter Zijlstra
2025-11-07 16:06 ` [PATCH 4/4] sched/fair: Proportional newidle balance Peter Zijlstra
2025-11-10 13:55   ` Dietmar Eggemann
2025-11-11  9:07   ` Adam Li
2025-11-11  9:20     ` Peter Zijlstra
2025-11-12 12:04       ` Adam Li
2025-11-12 13:41         ` Peter Zijlstra
2025-11-12 15:42   ` Shrikanth Hegde
2025-11-14  9:35     ` Peter Zijlstra
2025-11-14 12:18   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2025-11-17 16:23   ` tip-bot2 for Peter Zijlstra
2026-01-18 20:46   ` [PATCH 4/4] " Mario Roy
2026-01-23 10:50     ` Peter Zijlstra
2026-01-23 11:03       ` Peter Zijlstra
2026-01-23 12:24         ` K Prateek Nayak
2026-01-28  4:08           ` K Prateek Nayak
2026-01-27  4:15         ` Mario Roy
2026-01-27 10:40         ` Peter Zijlstra
2026-01-27 15:17           ` Peter Zijlstra
2026-01-30  1:44             ` Mario Roy
2026-01-30  4:14             ` Mario Roy
2026-02-24  9:13             ` [tip: sched/core] sched/fair: More complex proportional " tip-bot2 for Peter Zijlstra
2026-01-25 12:22     ` [PATCH 4/4] sched/fair: Proportional " Mohamed Abuelfotoh, Hazem
2026-01-27  8:44       ` Peter Zijlstra
2026-01-28 15:48         ` Mohamed Abuelfotoh, Hazem
2026-01-29  9:19           ` Peter Zijlstra
2026-01-29  9:24             ` Peter Zijlstra
2026-01-30 16:12               ` Mohamed Abuelfotoh, Hazem
2026-01-30 13:16             ` Mohamed Abuelfotoh, Hazem
2026-02-02 10:51               ` Peter Zijlstra
2026-02-02 11:07                 ` Mohamed Abuelfotoh, Hazem
2026-02-04 12:45                   ` Mohamed Abuelfotoh, Hazem
2026-02-04 13:27                     ` Peter Zijlstra
2026-02-04 13:59                       ` Mohamed Abuelfotoh, Hazem
2026-02-04 14:05                         ` Peter Zijlstra
2026-02-04 22:48                           ` Mohamed Abuelfotoh, Hazem
2026-01-27  8:50       ` Peter Zijlstra
2026-01-27  9:13         ` Peter Zijlstra
2026-01-28 16:24           ` Mohamed Abuelfotoh, Hazem
2026-01-28 16:03         ` Mohamed Abuelfotoh, Hazem
2026-04-29  8:51   ` Qing Wang
2026-05-06  2:44     ` [PATCH] sched/fair: Replace random newidle_balance with Bresenham accumulator Qing Wang
2025-11-10 19:47 ` [PATCH 0/4] sched: The newidle balance regression Chris Mason
2025-11-11 19:08 ` Josh Don
2025-11-12 21:59 ` Chris Mason
2025-11-14  9:37   ` Peter Zijlstra

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