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>
diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index 4b1b335..7fafd1b 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -116,14 +116,12 @@
# 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 @@
.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, \
\