net/neighbour: queue work on power efficient wq

Workqueue used in neighbour layer have no real dependency of scheduling these on
the cpu which scheduled them.

On a idle system, it is observed that an idle cpu wakes up many times just to
service this work. It would be better if we can schedule it on a cpu which the
scheduler believes to be the most appropriate one.

This patch replaces normal workqueues with power efficient versions. This
doesn't change existing behavior of code unless CONFIG_WQ_POWER_EFFICIENT is
enabled.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/neighbour.c

@@ -828,7 +828,7 @@ static void neigh_periodic_work(struct work_struct *work)
 	 * ARP entry timeouts range from 1/2 BASE_REACHABLE_TIME to 3/2
 	 * BASE_REACHABLE_TIME.
 	 */
-	schedule_delayed_work(&tbl->gc_work,
+	queue_delayed_work(system_power_efficient_wq, &tbl->gc_work,
 			      NEIGH_VAR(&tbl->parms, BASE_REACHABLE_TIME) >> 1);
 	write_unlock_bh(&tbl->lock);
 }
@@ -1565,7 +1565,8 @@ static void neigh_table_init_no_netlink(struct neigh_table *tbl)
 
 	rwlock_init(&tbl->lock);
 	INIT_DEFERRABLE_WORK(&tbl->gc_work, neigh_periodic_work);
-	schedule_delayed_work(&tbl->gc_work, tbl->parms.reachable_time);
+	queue_delayed_work(system_power_efficient_wq, &tbl->gc_work,
+			tbl->parms.reachable_time);
 	setup_timer(&tbl->proxy_timer, neigh_proxy_process, (unsigned long)tbl);
 	skb_queue_head_init_class(&tbl->proxy_queue,
 			&neigh_table_proxy_queue_class);