linux-kernel - [PATCH] tick/nohz: Optimize check_tick

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Message-ID: <20260128074558.15433-3-sunlightlinux@gmail.com>
Date: Wed, 28 Jan 2026 09:45:43 +0200
From: "Ionut Nechita (Sunlight Linux)" <sunlightlinux@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>
Cc: Ionut Nechita <sunlightlinux@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Ionut Nechita <ionut_n2001@...oo.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] tick/nohz: Optimize check_tick_dependency() with early return

Avoid iterating through individual tick dependency bits when the
tick_stop tracepoint is disabled, which is the common case. When
tracing is disabled, we can return immediately based on the atomic
value being zero or non-zero, skipping the per-bit evaluation.

This optimization improves the hot path performance of tick dependency
checks across all contexts (idle and non-idle), not just nohz_full CPUs.

Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ionut Nechita <ionut_n2001@...oo.com>
---
 kernel/time/tick-sched.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 34b341b66f220..2c1236a1cd364 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -332,6 +332,9 @@ static bool check_tick_dependency(atomic_t *dep)
 {
 	int val = atomic_read(dep);
 
+	if (likely(!tracepoint_enabled(tick_stop)))
+		return !val;
+
 	if (val & TICK_DEP_MASK_POSIX_TIMER) {
 		trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER);
 		return true;
-- 
2.52.0