sched: isolate SMP balancing code a bit more

At the moment, a lot of load balancing code that is irrelevant to non
SMP systems gets included during non SMP builds.

This patch addresses this issue and reduces the binary size on non
SMP systems:

   text    data     bss     dec     hex filename
  10983      28    1192   12203    2fab sched.o.before
  10739      28    1192   11959    2eb7 sched.o.after

Signed-off-by: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/sched.h

@@ -828,6 +828,7 @@ struct sched_class {
 	struct task_struct * (*pick_next_task) (struct rq *rq);
 	void (*put_prev_task) (struct rq *rq, struct task_struct *p);
 
+#ifdef CONFIG_SMP
 	unsigned long (*load_balance) (struct rq *this_rq, int this_cpu,
 			struct rq *busiest, unsigned long max_load_move,
 			struct sched_domain *sd, enum cpu_idle_type idle,
@@ -836,6 +837,7 @@ struct sched_class {
 	int (*move_one_task) (struct rq *this_rq, int this_cpu,
 			      struct rq *busiest, struct sched_domain *sd,
 			      enum cpu_idle_type idle);
+#endif
 
 	void (*set_curr_task) (struct rq *rq);
 	void (*task_tick) (struct rq *rq, struct task_struct *p);

kernel/sched.c

@@ -849,23 +849,6 @@ static int
 iter_move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
 		   struct sched_domain *sd, enum cpu_idle_type idle,
 		   struct rq_iterator *iterator);
-#else
-static inline unsigned long
-balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
-	      unsigned long max_load_move, struct sched_domain *sd,
-	      enum cpu_idle_type idle, int *all_pinned,
-	      int *this_best_prio, struct rq_iterator *iterator)
-{
-	return 0;
-}
-
-static inline int
-iter_move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
-		   struct sched_domain *sd, enum cpu_idle_type idle,
-		   struct rq_iterator *iterator)
-{
-	return 0;
-}
 #endif
 
 #include "sched_stats.h"

kernel/sched_fair.c

@@ -876,6 +876,7 @@ static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
 	}
 }
 
+#ifdef CONFIG_SMP
 /**************************************************
  * Fair scheduling class load-balancing methods:
  */
@@ -1008,6 +1009,7 @@ move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
 
 	return 0;
 }
+#endif
 
 /*
  * scheduler tick hitting a task of our scheduling class:
@@ -1084,8 +1086,10 @@ static const struct sched_class fair_sched_class = {
 	.pick_next_task		= pick_next_task_fair,
 	.put_prev_task		= put_prev_task_fair,
 
+#ifdef CONFIG_SMP
 	.load_balance		= load_balance_fair,
 	.move_one_task		= move_one_task_fair,
+#endif
 
 	.set_curr_task          = set_curr_task_fair,
 	.task_tick		= task_tick_fair,

kernel/sched_idletask.c

@@ -37,6 +37,7 @@ static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
 {
 }
 
+#ifdef CONFIG_SMP
 static unsigned long
 load_balance_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
 		  unsigned long max_load_move,
@@ -52,6 +53,7 @@ move_one_task_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
 {
 	return 0;
 }
+#endif
 
 static void task_tick_idle(struct rq *rq, struct task_struct *curr)
 {
@@ -76,8 +78,10 @@ const struct sched_class idle_sched_class = {
 	.pick_next_task		= pick_next_task_idle,
 	.put_prev_task		= put_prev_task_idle,
 
+#ifdef CONFIG_SMP
 	.load_balance		= load_balance_idle,
 	.move_one_task		= move_one_task_idle,
+#endif
 
 	.set_curr_task          = set_curr_task_idle,
 	.task_tick		= task_tick_idle,

kernel/sched_rt.c

@@ -98,6 +98,7 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
 	p->se.exec_start = 0;
 }
 
+#ifdef CONFIG_SMP
 /*
  * Load-balancing iterator. Note: while the runqueue stays locked
  * during the whole iteration, the current task might be
@@ -202,6 +203,7 @@ move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
 	return iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
 				  &rt_rq_iterator);
 }
+#endif
 
 static void task_tick_rt(struct rq *rq, struct task_struct *p)
 {
@@ -245,8 +247,10 @@ const struct sched_class rt_sched_class = {
 	.pick_next_task		= pick_next_task_rt,
 	.put_prev_task		= put_prev_task_rt,
 
+#ifdef CONFIG_SMP
 	.load_balance		= load_balance_rt,
 	.move_one_task		= move_one_task_rt,
+#endif
 
 	.set_curr_task          = set_curr_task_rt,
 	.task_tick		= task_tick_rt,