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

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 76fd964..13f48ee 100644 (file)
--- 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);
 }