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Commit d6d5cfaf authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

[PATCH] sched: less newidle locking 



Similarly to the earlier change in load_balance, only lock the runqueue in
load_balance_newidle if the busiest queue found has a nr_running > 1.  This
will reduce frequency of expensive remote runqueue lock aquisitions in the
schedule() path on some workloads.

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 67f9a619

kernel/sched.c

+10 −7
Original line number Original line Diff line number Diff line
@@ -2104,8 +2104,7 @@ static int load_balance(int this_cpu, runqueue_t *this_rq, 
		 */

		 */

		double_lock_balance(this_rq, busiest);

		double_lock_balance(this_rq, busiest);

		nr_moved = move_tasks(this_rq, this_cpu, busiest,

		nr_moved = move_tasks(this_rq, this_cpu, busiest,

						imbalance, sd, idle,

					imbalance, sd, idle, &all_pinned);

						&all_pinned);

		spin_unlock(&busiest->lock);

		spin_unlock(&busiest->lock);





		/* All tasks on this runqueue were pinned by CPU affinity */

		/* All tasks on this runqueue were pinned by CPU affinity */
@@ -2200,18 +2199,22 @@ static int load_balance_newidle(int this_cpu, runqueue_t *this_rq, 




	BUG_ON(busiest == this_rq);

	BUG_ON(busiest == this_rq);





	schedstat_add(sd, lb_imbalance[NEWLY_IDLE], imbalance);



	nr_moved = 0;

	if (busiest->nr_running > 1) {

		/* Attempt to move tasks */

		/* Attempt to move tasks */

		double_lock_balance(this_rq, busiest);

		double_lock_balance(this_rq, busiest);



	schedstat_add(sd, lb_imbalance[NEWLY_IDLE], imbalance);

		nr_moved = move_tasks(this_rq, this_cpu, busiest,

		nr_moved = move_tasks(this_rq, this_cpu, busiest,

					imbalance, sd, NEWLY_IDLE, NULL);

					imbalance, sd, NEWLY_IDLE, NULL);

		spin_unlock(&busiest->lock);

	}



	if (!nr_moved)

	if (!nr_moved)

		schedstat_inc(sd, lb_failed[NEWLY_IDLE]);

		schedstat_inc(sd, lb_failed[NEWLY_IDLE]);

	else

	else

		sd->nr_balance_failed = 0;

		sd->nr_balance_failed = 0;





	spin_unlock(&busiest->lock);

	return nr_moved;

	return nr_moved;





out_balanced:

out_balanced: