rcu: Move SRCU grace period work to power efficient workqueue

For better use of CPU idle time, allow the scheduler to select the CPU
on which the SRCU grace period work would be scheduled. This improves
idle residency time and conserves power.

This functionality is enabled when CONFIG_WQ_POWER_EFFICIENT is selected.

Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Shaibal Dutta <shaibal.dutta@broadcom.com>
[zoran.markovic@linaro.org: Rebased to latest kernel version. Added commit
message. Fixed code alignment.]
Signed-off-by: Zoran Markovic <zoran.markovic@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
index 5db7e9272d379bf3f6f139f4faf2e6be5b92c86b..2359779e1daac508ce21a09b6c01e85e32283952 100644 (file)
--- a/kernel/rcu/srcu.c
+++ b/kernel/rcu/srcu.c
@@ -398,7 +398,7 @@ void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
        rcu_batch_queue(&sp->batch_queue, head);
        if (!sp->running) {
                sp->running = true;
-               schedule_delayed_work(&sp->work, 0);
+               queue_delayed_work(system_power_efficient_wq, &sp->work, 0);
        }
        spin_unlock_irqrestore(&sp->queue_lock, flags);
 }
@@ -674,7 +674,8 @@ static void srcu_reschedule(struct srcu_struct *sp)
        }
 
        if (pending)
-               schedule_delayed_work(&sp->work, SRCU_INTERVAL);
+               queue_delayed_work(system_power_efficient_wq,
+                                  &sp->work, SRCU_INTERVAL);
 }
 
 /*