From 18d8cb64c9c074cbe2bd677ab10fff8283abdb62 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 16 Dec 2013 10:41:50 -0800 Subject: [PATCH] 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 Reviewed-by: Josh Triplett Acked-by: Peter Zijlstra Reviewed-by: Oleg Nesterov Reviewed-by: Steven Rostedt Tested-by: Mike Galbraith --- kernel/timer.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/timer.c b/kernel/timer.c index dfac34f7186f..0c638cf3d9d2 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -398,6 +398,7 @@ __internal_add_timer(struct tvec_base *base, struct timer_list *timer) static void internal_add_timer(struct tvec_base *base, struct timer_list *timer) { + (void)catchup_timer_jiffies(base); __internal_add_timer(base, timer); /* * Update base->active_timers and base->next_timer