linux-kernel - [PATCH V3 7/7] fbcon: queue work on any cpu

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Date:	Mon, 18 Mar 2013 20:53:29 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	pjt@...gle.com, paul.mckenney@...aro.org, tglx@...utronix.de,
	tj@...nel.org, suresh.b.siddha@...el.com, venki@...gle.com,
	mingo@...hat.com, peterz@...radead.org, rostedt@...dmis.org
Cc:	linaro-kernel@...ts.linaro.org, robin.randhawa@....com,
	Steve.Bannister@....com, Liviu.Dudau@....com,
	charles.garcia-tobin@....com, Arvind.Chauhan@....com,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Dave Airlie <airlied@...hat.com>, linux-fbdev@...r.kernel.org
Subject: [PATCH V3 7/7] fbcon: queue work on any cpu

fbcon uses workqueues and it has no real dependency of scheduling these on the
cpu which scheduled them.

On a idle system, it is observed that and idle cpu wakes up few times just to
service this work. It would be better if we can schedule it on a cpu which isn't
idle to save on power.

By idle cpu (from scheduler's perspective) we mean:
- Current task is idle task
- nr_running == 0
- wake_list is empty

This patch replaces schedule_work() routine with queue_work_on_any_cpu()
sibling with system_wq as workqueue.

This routine would look for the closest (via scheduling domains) non-idle cpu
(non-idle from schedulers perspective). If the current cpu is not idle or all
cpus are idle, work will be scheduled on local cpu.

Cc: Dave Airlie <airlied@...hat.com>
Cc: linux-fbdev@...r.kernel.org
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/video/console/fbcon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index 3cd6759..a900997 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -404,7 +404,7 @@ static void cursor_timer_handler(unsigned long dev_addr)
 	struct fb_info *info = (struct fb_info *) dev_addr;
 	struct fbcon_ops *ops = info->fbcon_par;
 
-	schedule_work(&info->queue);
+	queue_work_on_any_cpu(system_wq, &info->queue);
 	mod_timer(&ops->cursor_timer, jiffies + HZ/5);
 }
 
-- 
1.7.12.rc2.18.g61b472e

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