linux-kernel - [PATCH v2 2/3] sched/fair: Change likelyhood of nohz.nr

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Message-ID: <20260102124744.360872-3-sshegde@linux.ibm.com>
Date: Fri,  2 Jan 2026 18:17:43 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: mingo@...nel.org, peterz@...radead.org, vincent.guittot@...aro.org
Cc: sshegde@...ux.ibm.com, linux-kernel@...r.kernel.org,
        kprateek.nayak@....com, juri.lelli@...hat.com, vschneid@...hat.com,
        tglx@...utronix.de, dietmar.eggemann@....com, anna-maria@...utronix.de,
        frederic@...nel.org, wangyang.guo@...el.com
Subject: [PATCH v2 2/3] sched/fair: Change likelyhood of nohz.nr_cpus and do stats update if its due

These days most of the system have multi cores. The likelyhood of
at least one or more CPUs in nohz (idle state) is higher.
So move likely to unlikely.

Allow stats balancing to complete when there are no nr_cpus as the check
happens later. This may do an additional stats based load balancing
which would reset has_blocked_load. Code also looks saner by removing
that uncharactiristic return in between.

Signed-off-by: Shrikanth Hegde <sshegde@...ux.ibm.com>
---
 kernel/sched/fair.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index cd1c78d2c272..5ceb9126d441 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12456,10 +12456,10 @@ static void nohz_balancer_kick(struct rq *rq)
 
 	/*
 	 * None are in tickless mode and hence no need for NOHZ idle load
-	 * balancing:
+	 * balancing, do stats update if its due
 	 */
-	if (likely(!atomic_read(&nohz.nr_cpus)))
-		return;
+	if (unlikely(!atomic_read(&nohz.nr_cpus)))
+		goto out;
 
 	if (rq->nr_running >= 2) {
 		flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
-- 
2.47.3