sched: reduce balance-tasks overhead

At the moment, balance_tasks() provides low level functionality for both
  move_tasks() and move_one_task() (indirectly) via the load_balance()
function (in the sched_class interface) which also provides dual
functionality.  This dual functionality complicates the interfaces and
internal mechanisms and makes the run time overhead of operations that
are called with two run queue locks held.

This patch addresses this issue and reduces the overhead of these
operations.

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

1 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 52288a6..639241f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -829,11 +829,14 @@ struct sched_class {
 	void (*put_prev_task) (struct rq *rq, struct task_struct *p);
 
 	unsigned long (*load_balance) (struct rq *this_rq, int this_cpu,
-			struct rq *busiest,
-			unsigned long max_nr_move, unsigned long max_load_move,
+			struct rq *busiest, unsigned long max_load_move,
 			struct sched_domain *sd, enum cpu_idle_type idle,
 			int *all_pinned, int *this_best_prio);
 
+	int (*move_one_task) (struct rq *this_rq, int this_cpu,
+			      struct rq *busiest, struct sched_domain *sd,
+			      enum cpu_idle_type idle);
+
 	void (*set_curr_task) (struct rq *rq);
 	void (*task_tick) (struct rq *rq, struct task_struct *p);
 	void (*task_new) (struct rq *rq, struct task_struct *p);