timers: Reduce future __run_timers() latency for first add to empty list The __run_timers() function currently steps through the list one jiffy at a time in order to update the timer wheel. However, if the timer wheel is empty, no adjustment is needed other than updating ->timer_jiffies. Therefore, just before we add a timer to an empty timer wheel, we should mark the timer wheel as being up to date. This marking will reduce (and perhaps eliminate) the jiffy-stepping that a future __run_timers() call will need to do in response to some future timer posting or migration. This commit therefore updates ->timer_jiffies for this case. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/timer.c b/kernel/timer.c index bdd1c00..b49d2d0e8 100644 --- a/kernel/timer.c +++ b/kernel/timer.c
@@ -749,6 +749,7 @@ base = lock_timer_base(timer, &flags); + (void)catchup_timer_jiffies(base); ret = detach_if_pending(timer, base, false); if (!ret && pending_only) goto out_unlock;