From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 9 Oct 2024 08:28:54 +0000 (+0200)
Subject: timekeeping: Read NTP tick length only once
X-Git-Tag: v6.13-rc1~171^2~89
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=14f1e3b3dfc7fc8b61fcb79f956f05625af6f049;p=linux-block.git

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

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 1427c58e9802..2bc3542f29a2 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);
 	}