nohz: reduce jiffies polling overhead
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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 @@
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);