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

From: Viresh Kumar
Date: Mon Mar 18 2013 - 11:25:21 EST

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@xxxxxxxxxx>
Cc: linux-fbdev@xxxxxxxxxxxxxxx
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
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);


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