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Subject[RFC PATCH v4 6/7] sched: re-tune balancing -- revert
Date
commit 9fcd18c9e63e325dbd2b4c726623f760788d5aa8
Author: Ingo Molnar <mingo@elte.hu>
Date: Wed Nov 5 16:52:08 2008 +0100

Reverting this patch since this affects consolidation
and power savings. Will rework this tuning in the next
iteration.

Impact: improve wakeup affinity on NUMA systems, tweak SMP systems

Given the fixes+tweaks to the wakeup-buddy code, re-tweak the domain
balancing defaults on NUMA and SMP systems.

Turn on SD_WAKE_AFFINE which was off on x86 NUMA - there's no reason
why we would not want to have wakeup affinity across nodes as well.
(we already do this in the standard NUMA template.)

lat_ctx on a NUMA box is particularly happy about this change:

before:

| phoenix:~/l> ./lat_ctx -s 0 2
| "size=0k ovr=2.60
| 2 5.70

after:

| phoenix:~/l> ./lat_ctx -s 0 2
| "size=0k ovr=2.65
| 2 2.07

a 2.75x speedup.

pipe-test is similarly happy about it too:

| phoenix:~/sched-tests> ./pipe-test
| 18.26 usecs/loop.
| 14.70 usecs/loop.
| 14.38 usecs/loop.
| 10.55 usecs/loop. # +WAKE_AFFINE on domain0+domain1
| 8.63 usecs/loop.
| 8.59 usecs/loop.
| 9.03 usecs/loop.
| 8.94 usecs/loop.
| 8.96 usecs/loop.
| 8.63 usecs/loop.

Also:

- disable SD_BALANCE_NEWIDLE on NUMA and SMP domains (keep it for siblings)
- enable SD_WAKE_BALANCE on SMP domains

Sysbench+postgresql improves all around the board, quite significantly:

.28-rc3-11474e2c .28-rc3-11474e2c-tune
-------------------------------------------------
1: 571 688 +17.08%
2: 1236 1206 -2.55%
4: 2381 2642 +9.89%
8: 4958 5164 +3.99%
16: 9580 9574 -0.07%
32: 7128 8118 +12.20%
64: 7342 8266 +11.18%
128: 7342 8064 +8.95%
256: 7519 7884 +4.62%
512: 7350 7731 +4.93%
-------------------------------------------------
SUM: 55412 59341 +6.62%

So it's a win both for the runup portion, the peak area and the tail.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
---

arch/x86/include/asm/topology.h | 7 +++----
include/linux/topology.h | 4 ++--
2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index 4850e4b..90ac771 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -154,7 +154,7 @@ extern unsigned long node_remap_size[];

#endif

-/* sched_domains SD_NODE_INIT for NUMA machines */
+/* sched_domains SD_NODE_INIT for NUMAQ machines */
#define SD_NODE_INIT (struct sched_domain) { \
.min_interval = 8, \
.max_interval = 32, \
@@ -169,9 +169,8 @@ extern unsigned long node_remap_size[];
.flags = SD_LOAD_BALANCE \
| SD_BALANCE_EXEC \
| SD_BALANCE_FORK \
- | SD_WAKE_AFFINE \
- | SD_WAKE_BALANCE \
- | SD_SERIALIZE, \
+ | SD_SERIALIZE \
+ | SD_WAKE_BALANCE, \
.last_balance = jiffies, \
.balance_interval = 1, \
}
diff --git a/include/linux/topology.h b/include/linux/topology.h
index 117f1b7..2565f4a 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -146,10 +146,10 @@ void arch_update_cpu_topology(void);
.wake_idx = 1, \
.forkexec_idx = 1, \
.flags = SD_LOAD_BALANCE \
- | SD_BALANCE_EXEC \
+ | SD_BALANCE_NEWIDLE \
| SD_BALANCE_FORK \
+ | SD_BALANCE_EXEC \
| SD_WAKE_AFFINE \
- | SD_WAKE_BALANCE \
| BALANCE_FOR_PKG_POWER,\
.last_balance = jiffies, \
.balance_interval = 1, \


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