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>

1 files changed, 1 insertions, 3 deletions

diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index 4b1b335097b5..7fafd1bc4149 100644
--- a/arch/x86/include/asm/topology.h
+++ b/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,                      \
                                                                         \