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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-12-16 10:41:50 -0800
committerAnders Roxell <anders.roxell@linaro.org>2015-06-01 12:03:38 +0200
commit9578c849d400eaaaffcf0e757244baeeb8b0a35a (patch)
parent2d74a9576e3931c2249467485ab54b3b2530ed69 (diff)
timers: Reduce future __run_timers() latency for first add to empty list
upstream commit: 18d8cb64c9c074cbe2bd677ab10fff8283abdb62 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> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Tested-by: Mike Galbraith <bitbucket@online.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/timer.c b/kernel/timer.c
index 380f125ad100..2059f6b27595 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -401,6 +401,7 @@ __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