linux-kernel - [tip: sched/core] sched/fair: Limit hrtick work

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Message-ID: <176569840329.498.11558609512617664315.tip-bot2@tip-bot2>
Date: Sun, 14 Dec 2025 07:46:43 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Ingo Molnar <mingo@...nel.org>, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/fair: Limit hrtick work

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     95a0155224a658965f34ed4b1943b238d9be1fea
Gitweb:        https://git.kernel.org/tip/95a0155224a658965f34ed4b1943b238d9be1fea
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Mon, 01 Sep 2025 22:50:56 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Sun, 14 Dec 2025 08:25:02 +01:00

sched/fair: Limit hrtick work

The task_tick_fair() function does:

 - update the hierarchical runtimes
 - drive NUMA-balancing
 - update load-balance statistics
 - drive force-idle preemption

All but the very first can be limited to the periodic tick. Let hrtick
only update accounting and drive preemption, not load-balancing and
other bits.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://patch.msgid.link/20250918080205.563385766@infradead.org
---
 kernel/sched/fair.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 496a30a..f79951f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -13332,6 +13332,12 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
 		entity_tick(cfs_rq, se, queued);
 	}
 
+	if (queued) {
+		if (!need_resched())
+			hrtick_start_fair(rq, curr);
+		return;
+	}
+
 	if (static_branch_unlikely(&sched_numa_balancing))
 		task_tick_numa(rq, curr);