sched: Improve latencies and throughput

Make the idle balancer more agressive, to improve a
x264 encoding workload provided by Jason Garrett-Glaser:

 NEXT_BUDDY NO_LB_BIAS
 encoded 600 frames, 252.82 fps, 22096.60 kb/s
 encoded 600 frames, 250.69 fps, 22096.60 kb/s
 encoded 600 frames, 245.76 fps, 22096.60 kb/s

 NO_NEXT_BUDDY LB_BIAS
 encoded 600 frames, 344.44 fps, 22096.60 kb/s
 encoded 600 frames, 346.66 fps, 22096.60 kb/s
 encoded 600 frames, 352.59 fps, 22096.60 kb/s

 NO_NEXT_BUDDY NO_LB_BIAS
 encoded 600 frames, 425.75 fps, 22096.60 kb/s
 encoded 600 frames, 425.45 fps, 22096.60 kb/s
 encoded 600 frames, 422.49 fps, 22096.60 kb/s

Peter pointed out that this is better done via newidle_idx,
not via LB_BIAS, newidle balancing should look for where
there is load _now_, not where there was load 2 ticks ago.

Worst-case latencies are improved as well as no buddies
means less vruntime spread. (as per prior lkml discussions)

This change improves kbuild-peak parallelism as well.

Reported-by: Jason Garrett-Glaser <darkshikari@gmail.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1253011667.9128.16.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/ia64/include/asm/topology.h

@@ -61,7 +61,7 @@ void build_cpu_to_node_map(void);
 	.cache_nice_tries	= 2,			\
 	.busy_idx		= 2,			\
 	.idle_idx		= 1,			\
-	.newidle_idx		= 2,			\
+	.newidle_idx		= 0,			\
 	.wake_idx		= 0,			\
 	.forkexec_idx		= 1,			\
 	.flags			= SD_LOAD_BALANCE	\
@@ -87,10 +87,11 @@ void build_cpu_to_node_map(void);
 	.cache_nice_tries	= 2,			\
 	.busy_idx		= 3,			\
 	.idle_idx		= 2,			\
-	.newidle_idx		= 2,			\
+	.newidle_idx		= 0,			\
 	.wake_idx		= 0,			\
 	.forkexec_idx		= 1,			\
 	.flags			= SD_LOAD_BALANCE	\
+				| SD_BALANCE_NEWIDLE	\
 				| SD_BALANCE_EXEC	\
 				| SD_BALANCE_FORK	\
 				| SD_BALANCE_WAKE	\

arch/powerpc/include/asm/topology.h

@@ -57,7 +57,7 @@ static inline int pcibus_to_node(struct pci_bus *bus)
 	.cache_nice_tries	= 1,			\
 	.busy_idx		= 3,			\
 	.idle_idx		= 1,			\
-	.newidle_idx		= 2,			\
+	.newidle_idx		= 0,			\
 	.wake_idx		= 0,			\
 	.flags			= SD_LOAD_BALANCE	\
 				| SD_BALANCE_EXEC	\

arch/sh/include/asm/topology.h

@@ -15,13 +15,14 @@
 	.cache_nice_tries	= 2,			\
 	.busy_idx		= 3,			\
 	.idle_idx		= 2,			\
-	.newidle_idx		= 2,			\
+	.newidle_idx		= 0,			\
 	.wake_idx		= 0,			\
 	.forkexec_idx		= 1,			\
 	.flags			= SD_LOAD_BALANCE	\
 				| SD_BALANCE_FORK	\
 				| SD_BALANCE_EXEC	\
 				| SD_BALANCE_WAKE	\
+				| SD_BALANCE_NEWIDLE	\
 				| SD_SERIALIZE,		\
 	.last_balance		= jiffies,		\
 	.balance_interval	= 1,			\

arch/x86/include/asm/topology.h

@@ -116,14 +116,12 @@ extern unsigned long node_remap_size[];
 
 # define SD_CACHE_NICE_TRIES	1
 # define SD_IDLE_IDX		1
-# define SD_NEWIDLE_IDX		2
 # define SD_FORKEXEC_IDX	0
 
 #else
 
 # define SD_CACHE_NICE_TRIES	2
 # define SD_IDLE_IDX		2
-# define SD_NEWIDLE_IDX		2
 # define SD_FORKEXEC_IDX	1
 
 #endif
@@ -137,7 +135,7 @@ extern unsigned long node_remap_size[];
 	.cache_nice_tries	= SD_CACHE_NICE_TRIES,			\
 	.busy_idx		= 3,					\
 	.idle_idx		= SD_IDLE_IDX,				\
-	.newidle_idx		= SD_NEWIDLE_IDX,			\
+	.newidle_idx		= 0,					\
 	.wake_idx		= 0,					\
 	.forkexec_idx		= SD_FORKEXEC_IDX,			\
 									\

include/linux/topology.h

@@ -151,7 +151,7 @@ int arch_update_cpu_topology(void);
 	.cache_nice_tries	= 1,					\
 	.busy_idx		= 2,					\
 	.idle_idx		= 1,					\
-	.newidle_idx		= 2,					\
+	.newidle_idx		= 0,					\
 	.wake_idx		= 0,					\
 	.forkexec_idx		= 1,					\
 									\

kernel/sched_features.h

@@ -67,7 +67,7 @@ SCHED_FEAT(AFFINE_WAKEUPS, 1)
  * wakeup-preemption), since its likely going to consume data we
  * touched, increases cache locality.
  */
-SCHED_FEAT(NEXT_BUDDY, 1)
+SCHED_FEAT(NEXT_BUDDY, 0)
 
 /*
  * Prefer to schedule the task that ran last (when we did