linux-kernel - [PATCH V3 5/7] mmc: queue work on any cpu

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Date:	Mon, 18 Mar 2013 20:53:27 +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>,
	Chris Ball <cjb@...top.org>, linux-mmc@...r.kernel.org
Subject: [PATCH V3 5/7] mmc: queue work on any cpu

mmc uses workqueues for running mmc_rescan(). There is 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 many 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 the queue_delayed_work() with
queue_delayed_work_on_any_cpu() siblings.

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: Chris Ball <cjb@...top.org>
Cc: linux-mmc@...r.kernel.org
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/mmc/core/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 9290bb5..adf331a 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -85,7 +85,7 @@ MODULE_PARM_DESC(
 static int mmc_schedule_delayed_work(struct delayed_work *work,
 				     unsigned long delay)
 {
-	return queue_delayed_work(workqueue, work, delay);
+	return queue_delayed_work_on_any_cpu(workqueue, work, delay);
 }
 
 /*
-- 
1.7.12.rc2.18.g61b472e

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