linux-kernel - [tip: timers/core] timers: Reuse next expiry cache after nohz exit

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Message-ID: <159501601744.4006.18407986100047143357.tip-bot2@tip-bot2>
Date:   Fri, 17 Jul 2020 20:00:17 -0000
From:   "tip-bot2 for Frederic Weisbecker" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Juri Lelli <juri.lelli@...hat.com>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: timers/core] timers: Reuse next expiry cache after nohz exit

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

Commit-ID:     90d52f65f303091be17b5f4ffab7090b2064b4a1
Gitweb:        https://git.kernel.org/tip/90d52f65f303091be17b5f4ffab7090b2064b4a1
Author:        Frederic Weisbecker <frederic@...nel.org>
AuthorDate:    Fri, 17 Jul 2020 16:05:47 +02:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Fri, 17 Jul 2020 21:55:23 +02:00

timers: Reuse next expiry cache after nohz exit

Now that the next expiry it tracked unconditionally when a timer is added,
this information can be reused on a tick firing after exiting nohz.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Juri Lelli <juri.lelli@...hat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-9-frederic@kernel.org

---
 kernel/time/timer.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 76fd964..13f48ee 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1706,13 +1706,11 @@ static int collect_expired_timers(struct timer_base *base,
 	 * the next expiring timer.
 	 */
 	if ((long)(now - base->clk) > 2) {
-		unsigned long next = __next_timer_interrupt(base);
-
 		/*
 		 * If the next timer is ahead of time forward to current
 		 * jiffies, otherwise forward to the next expiry time:
 		 */
-		if (time_after(next, now)) {
+		if (time_after(base->next_expiry, now)) {
 			/*
 			 * The call site will increment base->clk and then
 			 * terminate the expiry loop immediately.
@@ -1720,7 +1718,7 @@ static int collect_expired_timers(struct timer_base *base,
 			base->clk = now;
 			return 0;
 		}
-		base->clk = next;
+		base->clk = base->next_expiry;
 	}
 	return __collect_expired_timers(base, heads);
 }