[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: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/sched.c b/kernel/sched.c
index c61ee34..9301895 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2104,8 +2104,7 @@
*/
double_lock_balance(this_rq, busiest);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
- imbalance, sd, idle,
- &all_pinned);
+ imbalance, sd, idle, &all_pinned);
spin_unlock(&busiest->lock);
/* All tasks on this runqueue were pinned by CPU affinity */
@@ -2200,18 +2199,22 @@
BUG_ON(busiest == this_rq);
- /* Attempt to move tasks */
- 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 = 0;
+ if (busiest->nr_running > 1) {
+ /* Attempt to move tasks */
+ double_lock_balance(this_rq, busiest);
+ nr_moved = move_tasks(this_rq, this_cpu, busiest,
imbalance, sd, NEWLY_IDLE, NULL);
+ spin_unlock(&busiest->lock);
+ }
+
if (!nr_moved)
schedstat_inc(sd, lb_failed[NEWLY_IDLE]);
else
sd->nr_balance_failed = 0;
- spin_unlock(&busiest->lock);
return nr_moved;
out_balanced:
