[PATCH] sched: reduce active load balancing

Fix up active load balancing a bit so it doesn't get called when it shouldn't.
Reset the nr_balance_failed counter at more points where we have found
conditions to be balanced.  This reduces too aggressive active balancing seen
on some workloads.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 6 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 2794c79b9197..03d737791c1a 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2021,6 +2021,7 @@ out_balanced:
 
         schedstat_inc(sd, lb_balanced[idle]);
 
+        sd->nr_balance_failed = 0;
         /* tune up the balancing interval */
         if (sd->balance_interval < sd->max_interval)
                 sd->balance_interval *= 2;
@@ -2046,16 +2047,14 @@ static int load_balance_newidle(int this_cpu, runqueue_t *this_rq,
         schedstat_inc(sd, lb_cnt[NEWLY_IDLE]);
         group = find_busiest_group(sd, this_cpu, &imbalance, NEWLY_IDLE);
         if (!group) {
-                schedstat_inc(sd, lb_balanced[NEWLY_IDLE]);
                 schedstat_inc(sd, lb_nobusyg[NEWLY_IDLE]);
-                goto out;
+                goto out_balanced;
         }
 
         busiest = find_busiest_queue(group);
         if (!busiest || busiest == this_rq) {
-                schedstat_inc(sd, lb_balanced[NEWLY_IDLE]);
                 schedstat_inc(sd, lb_nobusyq[NEWLY_IDLE]);
-                goto out;
+                goto out_balanced;
         }
 
         /* Attempt to move tasks */
@@ -2066,11 +2065,16 @@ static int load_balance_newidle(int this_cpu, runqueue_t *this_rq,
                                         imbalance, sd, NEWLY_IDLE, NULL);
         if (!nr_moved)
                 schedstat_inc(sd, lb_failed[NEWLY_IDLE]);
+        else
+                sd->nr_balance_failed = 0;
 
         spin_unlock(&busiest->lock);
-
-out:
         return nr_moved;
+
+out_balanced:
+        schedstat_inc(sd, lb_balanced[NEWLY_IDLE]);
+        sd->nr_balance_failed = 0;
+        return 0;
 }
 
 /*