linux-kernel - Re: [PATCH 2/4] sched/fair: Small cleanup to sched_balance

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Message-ID: <20251112150818.GG4068168@noisy.programming.kicks-ass.net>
Date: Wed, 12 Nov 2025 16:08:18 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: mingo@...hat.com, 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,
	Chris Mason <clm@...a.com>,
	Joseph Salisbury <joseph.salisbury@...cle.com>,
	Adam Li <adamli@...amperecomputing.com>,
	Hazem Mohamed Abuelfotoh <abuehaze@...zon.com>,
	Josh Don <joshdon@...gle.com>
Subject: Re: [PATCH 2/4] sched/fair: Small cleanup to sched_balance_newidle()

On Wed, Nov 12, 2025 at 03:42:41PM +0100, Peter Zijlstra wrote:

> > if sd is null, i think we are skipping these compared to earlier.
> > 
> >         t0 = sched_clock_cpu(this_cpu);
> >         sched_balance_update_blocked_averages(this_cpu);
> 
> let me pull that sched_balance_update_blocked_averages() thing up a few
> lines.

Something like so..

---
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9946,15 +9946,11 @@ static unsigned long task_h_load(struct
 }
 #endif /* !CONFIG_FAIR_GROUP_SCHED */
 
-static void sched_balance_update_blocked_averages(int cpu)
+static void __sched_balance_update_blocked_averages(struct rq *rq)
 {
 	bool decayed = false, done = true;
-	struct rq *rq = cpu_rq(cpu);
-	struct rq_flags rf;
 
-	rq_lock_irqsave(rq, &rf);
 	update_blocked_load_tick(rq);
-	update_rq_clock(rq);
 
 	decayed |= __update_blocked_others(rq, &done);
 	decayed |= __update_blocked_fair(rq, &done);
@@ -9962,7 +9958,15 @@ static void sched_balance_update_blocked
 	update_blocked_load_status(rq, !done);
 	if (decayed)
 		cpufreq_update_util(rq, 0);
-	rq_unlock_irqrestore(rq, &rf);
+}
+
+static void sched_balance_update_blocked_averages(int cpu)
+{
+	struct rq *rq = cpu_rq(cpu);
+
+	guard(rq_lock_irqsave)(rq);
+	update_rq_clock(rq);
+	__sched_balance_update_blocked_averages(rq);
 }
 
 /********** Helpers for sched_balance_find_src_group ************************/
@@ -12865,6 +12869,8 @@ static int sched_balance_newidle(struct
 	if (!cpu_active(this_cpu))
 		return 0;
 
+	__sched_balance_update_blocked_averages(this_rq);
+
 	/*
 	 * This is OK, because current is on_cpu, which avoids it being picked
 	 * for load-balance and preemption/IRQs are still disabled avoiding
@@ -12891,7 +12897,6 @@ static int sched_balance_newidle(struct
 	raw_spin_rq_unlock(this_rq);
 
 	t0 = sched_clock_cpu(this_cpu);
-	sched_balance_update_blocked_averages(this_cpu);
 
 	rcu_read_lock();
 	for_each_domain(this_cpu, sd) {