[PATCH V2 2/2] mm: add FAULT_AROUND_ORDER Kconfig paramater for powerpc

From: Madhavan Srinivasan
Date: Fri Apr 04 2014 - 02:27:51 EST

Performance data for different FAULT_AROUND_ORDER values from 4 socket
Power7 system (128 Threads and 128GB memory) is below. perf stat with
repeat of 5 is used to get the stddev values. This patch create
FAULT_AROUND_ORDER Kconfig parameter and defaults it to 3 based on the
performance data.

FAULT_AROUND_ORDER Baseline 1 3 4 5 7

Linux build (make -j64)
minor-faults 7184385 5874015 4567289 4318518 4193815 4159193
times in seconds 61.433776136 60.865935292 59.245368038 60.630675011 60.56587624 59.828271924
stddev for time ( +- 1.18% ) ( +- 1.78% ) ( +- 0.44% ) ( +- 2.03% ) ( +- 1.66% ) ( +- 1.45% )

Linux rebuild (make -j64)
minor-faults 303018 226392 146170 132480 126878 126236
times in seconds 5.659819172 5.723996942 5.591238319 5.622533357 5.878811995 5.550133096
stddev for time ( +- 0.71% ) ( +- 0.78% ) ( +- 0.62% ) ( +- 0.45% ) ( +- 1.55% ) ( +- 0.29% )

Two synthetic tests: access every word in file in sequential/random order.
Marginal Performance gains seen for FAO value of 3 when compared to value
of 4.

Sequential access 16GiB file
FAULT_AROUND_ORDER Baseline 1 3 4 5 7
1 thread
minor-faults 262302 131192 32873 16486 8291 2351
times in seconds 53.071497352 52.945826882 52.931417302 52.928577184 52.859285439 53.116800539
stddev for time ( +- 0.01% ) ( +- 0.02% ) ( +- 0.02% ) ( +- 0.04% ) ( +- 0.04% ) ( +- 0.01% )
8 threads
minor-faults 2097314 1051046 263336 131715 66098 16653
times in seconds 54.385698561 54.603652339 54.771282004 54.488565674 54.496701531 54.962142189
stddev for time ( +- 0.05% ) ( +- 0.02% ) ( +- 0.37% ) ( +- 0.08% ) ( +- 0.07% ) ( +- 0.51% )
32 threads
minor-faults 8389267 4218595 1059961 531319 266463 67271
times in seconds 60.61715047 60.827964038 60.46412673 60.266045885 60.492398315 60.24531921
stddev for time ( +- 0.65% ) ( +- 0.21% ) ( +- 0.25% ) ( +- 0.29% ) ( +- 0.19% ) ( +- 0.35% )
64 threads
minor-faults 16777455 8485998 2178582 1092106 544302 137693
times in seconds 86.471334554 84.412415735 85.208303832 84.331473392 85.598793479 84.695469266
stddev for time ( +- 0.60% ) ( +- 1.47% ) ( +- 0.74% ) ( +- 1.55% ) ( +- 0.92% ) ( +- 1.16% )
128 threads
minor-faults 33555267 17734522 4710107 2380821 1182707 292077
times in seconds 117.535385569 114.291359037 112.593908276 113.081807611 114.358686588 114.491043011
stddev for time ( +- 2.24% ) ( +- 0.92% ) ( +- 0.36% ) ( +- 0.53% ) ( +- 0.70% ) ( +- 0.53% )

Random access 1GiB file
FAULT_AROUND_ORDER Baseline 1 3 4 5 7
1 thread
minor-faults 16503 8664 2149 1126 610 437
times in seconds 43.843573808 48.042069805 50.580779682 54.282884593 52.641739876 51.803302129
stddev for time ( +- 1.30% ) ( +- 2.25% ) ( +- 2.92% ) ( +- 1.44% ) ( +- 4.49% ) ( +- 3.78% )
8 threads
minor-faults 131201 70916 17760 8665 4250 1149
times in seconds 46.262626804 55.942851041 56.629191584 57.97044714 55.417557594 56.019709166
stddev for time ( +- 4.66% ) ( +- 1.52% ) ( +- 1.43% ) ( +- 1.61% ) ( +- 0.65% ) ( +- 1.27% )
32 threads
minor-faults 524959 265980 67282 33601 16930 4316
times in seconds 67.754175928 69.85012331 71.750338061 71.053074643 68.90728294 71.250103217
stddev for time ( +- 3.79% ) ( +- 0.77% ) ( +- 1.15% ) ( +- 1.08% ) ( +- 2.14% ) ( +- 1.17% )
64 threads
minor-faults 1048831 528829 133256 66700 33428 8776
times in seconds 96.674025305 93.109961822 87.441777715 91.986332028 88.686748472 93.101434306
stddev for time ( +- 2.85% ) ( +- 2.42% ) ( +- 0.42% ) ( +- 1.58% ) ( +- 1.29% ) ( +- 2.01% )
128 threads
minor-faults 2098043 1053224 266271 133702 66966 17276
times in seconds 156.525792044 152.117971403 147.523673243 148.560226602 148.596575663 149.389288429
stddev for time ( +- 2.39% ) ( +- 0.71% ) ( +- 0.72% ) ( +- 0.35% ) ( +- 0.41% ) ( +- 1.04% )

Worst case scenario: we touch one page every 16M to demonstrate overhead.

Touch only one page in page table in 16GiB file
FAULT_AROUND_ORDER Baseline 1 3 4 5 7
1 thread
minor-faults 1077 1064 1051 1048 1046 1045
times in seconds 0.00615347 0.008327379 0.019775282 0.034444003 0.05905971 0.220863339
stddev for time ( +- 3.12% ) ( +- 2.29% ) ( +- 1.68% ) ( +- 1.40% ) ( +- 1.68% ) ( +- 1.53% )
8 threads
minor-faults 8252 8239 8226 8223 8220 8224
times in seconds 0.04387392 0.059859294 0.113897648 0.199707764 0.361585762 1.343366843
stddev for time ( +- 3.66% ) ( +- 2.18% ) ( +- 1.44% ) ( +- 2.40% ) ( +- 2.08% ) ( +- 1.75% )
32 threads
minor-faults 32852 32841 32825 32826 32824 32828
times in seconds 0.191404544 0.21907773 0.433207123 0.72430447 1.334983196 4.97727449
stddev for time ( +- 5.08% ) ( +- 3.19% ) ( +- 4.45% ) ( +- 2.18% ) ( +- 2.75% ) ( +- 1.52% )
64 threads
minor-faults 65652 65642 65629 65622 65623 65634
times in seconds 0.402140429 0.510806718 0.854288645 1.412329805 2.556707704 8.711074863
stddev for time ( +- 2.90% ) ( +- 3.04% ) ( +- 1.83% ) ( +- 2.75% ) ( +- 2.49% ) ( +- 0.68% )
128 threads
minor-faults 131255 131239 131228 131228 131229 131243
times in seconds 0.817782148 1.124631348 2.023730928 3.184792382 5.331392072 17.309524609
stddev for time ( +- 3.35% ) ( +- 11.74% ) ( +- 4.55% ) ( +- 2.00% ) ( +- 1.31% ) ( +- 1.30% )

Signed-off-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
---
arch/powerpc/platforms/pseries/Kconfig | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig
index 2cb8b77..2246d9f 100644
--- a/arch/powerpc/platforms/pseries/Kconfig
+++ b/arch/powerpc/platforms/pseries/Kconfig
@@ -132,3 +132,8 @@ config DTL
which are accessible through a debugfs file.

Say N if you are unsure.
+
+config FAULT_AROUND_ORDER
+ int
+ default "3"
+
--
1.7.10.4

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