Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Frederic Weisbecker <frederic@kernel.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        Anna-Maria Gleixner <anna-maria@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>
Subject: [PATCH 5/9] timer: Reuse next expiry cache after nohz exit
Date:   Tue,  7 Jul 2020 03:32:49 +0200
Message-Id: <20200707013253.26770-6-frederic@kernel.org>
In-Reply-To: <20200707013253.26770-1-frederic@kernel.org>
References: <20200707013253.26770-1-frederic@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Now that we track the next expiry unconditionally when a timer is added,
we can reuse that information on a tick firing after exiting nohz.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Juri Lelli <juri.lelli@redhat.com>
---
 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 8a4138e47aa4..501d36ef0b75 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1705,13 +1705,11 @@ 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.
@@ -1719,7 +1717,7 @@ 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);
 }
-- 
2.26.2