[PATCH] sched: reduce node balancing interval

From: Nick Piggin <nickpiggin@yahoo.com.au>

From: Suresh Siddha <suresh.b.siddha@intel.com>

Node max rebalance interval is too large.  It is currently dependent on
number of online cpus.  For 16 cpu system, max node balance interval in
busy case is 32 seconds.  Agreed that it will use max 32 seconds only when
it doesn't find imbalance for a long time.  But this will lead to slow
response time in cases where load runs for a second with no imbalance and
suddently creates an imbalance.  My patch makes the busy max node rebalance
interval equal to the base [scheduler].

include/linux/sched.h

@@ -640,7 +640,7 @@ struct sched_domain {
 	.parent			= NULL,			\
 	.groups			= NULL,			\
 	.min_interval		= 8,			\
-	.max_interval		= 256*fls(num_online_cpus()),\
+	.max_interval		= 32,			\
 	.busy_factor		= 32,			\
 	.imbalance_pct		= 125,			\
 	.cache_hot_time		= (10*1000000),		\