linux-kernel - [tip: timers/core] timekeeping: Read NTP tick length only once

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Message-ID: <172987929055.1442.14883159884487157363.tip-bot2@tip-bot2>
Date: Fri, 25 Oct 2024 18:01:30 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
 "Anna-Maria Behnsen" <anna-maria@...utronix.de>,
 John Stultz <jstultz@...gle.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: timers/core] timekeeping: Read NTP tick length only once

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

Commit-ID:     14f1e3b3dfc7fc8b61fcb79f956f05625af6f049
Gitweb:        https://git.kernel.org/tip/14f1e3b3dfc7fc8b61fcb79f956f05625af6f049
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Wed, 09 Oct 2024 10:28:54 +02:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Fri, 25 Oct 2024 19:49:12 +02:00

timekeeping: Read NTP tick length only once

No point in reading it a second time when the comparison fails.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: John Stultz <jstultz@...gle.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-1-554456a44a15@linutronix.de

---
 kernel/time/timekeeping.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 1427c58..2bc3542 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -2161,16 +2161,17 @@ static __always_inline void timekeeping_apply_adjustment(struct timekeeper *tk,
  */
 static void timekeeping_adjust(struct timekeeper *tk, s64 offset)
 {
+	u64 ntp_tl = ntp_tick_length();
 	u32 mult;
 
 	/*
 	 * Determine the multiplier from the current NTP tick length.
 	 * Avoid expensive division when the tick length doesn't change.
 	 */
-	if (likely(tk->ntp_tick == ntp_tick_length())) {
+	if (likely(tk->ntp_tick == ntp_tl)) {
 		mult = tk->tkr_mono.mult - tk->ntp_err_mult;
 	} else {
-		tk->ntp_tick = ntp_tick_length();
+		tk->ntp_tick = ntp_tl;
 		mult = div64_u64((tk->ntp_tick >> tk->ntp_error_shift) -
 				 tk->xtime_remainder, tk->cycle_interval);
 	}