nohz: reduce jiffies polling overhead

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 0 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index b854a89..cb75394 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -48,6 +48,13 @@ static void tick_do_update_jiffies64(ktime_t now)
 	unsigned long ticks = 0;
 	ktime_t delta;
 
+	/*
+	 * Do a quick check without holding xtime_lock:
+	 */
+	delta = ktime_sub(now, last_jiffies_update);
+	if (delta.tv64 < tick_period.tv64)
+		return;
+
 	/* Reevalute with xtime_lock held */
 	write_seqlock(&xtime_lock);