Commit-ID: 18d8cb64c9c074cbe2bd677ab10fff8283abdb62
Gitweb: http://git.kernel.org/tip/18d8cb64c9c074cbe2bd677ab10fff8283abdb62
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 16 Dec 2013 10:41:50 -0800
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 25 Feb 2014 12:39:00 -0800
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@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Reviewed-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Reviewed-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Tested-by: Mike Galbraith <bitbucket@xxxxxxxxx>
---
kernel/timer.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/timer.c b/kernel/timer.c
index dfac34f..0c638cf 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
--
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