lkml.org 
[lkml]   [2015]   [Mar]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH RT 30/31] timers: Reduce future __run_timers() latency for first add to empty list
3.10.70-rt75-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

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>
---
kernel/timer.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/kernel/timer.c b/kernel/timer.c
index 39f5caef6714..06050920aee5 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
--
2.1.4



\
 
 \ /
  Last update: 2015-03-13 16:41    [W:0.074 / U:9.156 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site