3-5% increased netperf throughput by "sched: Micro-optimize thesmart wake-affine logic"

From: Fengguang Wu
Date: Sat Sep 07 2013 - 08:38:39 EST

Hi Peter,

We are glad to report some measurable performance improvements by your
commit

commit 7d9ffa8961482232d964173cccba6e14d2d543b2
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Thu Jul 4 12:56:46 2013 +0800

sched: Micro-optimize the smart wake-affine logic

Smart wake-affine is using node-size as the factor currently, but the overhead
of the mask operation is high.

Thus, this patch introduce the 'sd_llc_size' percpu variable, which will record
the highest cache-share domain size, and make it to be the new factor, in order
to reduce the overhead and make it more reasonable.

Tested-by: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Tested-by: Michael Wang <wangyun@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Acked-by: Michael Wang <wangyun@xxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Link: http://lkml.kernel.org/r/51D5008E.6030102@xxxxxxxxxxxxxxxxxx
[ Tidied up the changelog. ]
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>

:040000 040000 e7c8a8c55bfa1261f3c6b75674a83eb76bb88a3f 129777b8d0b74ce189760ad76d9aaecd65b7ee7f M kernel
bisect run success

# bad: [37570e7ef5be99ba5188bb17ed547ac4bbf65e73] Merge remote-tracking branch 'nfc-next/master' into devel-hourly-2013090406
# good: [6e4664525b1db28f8c4e1130957f70a94c19213e] Linux 3.11
git bisect start '37570e7ef5be99ba5188bb17ed547ac4bbf65e73' '6e4664525b1db28f8c4e1130957f70a94c19213e' '--'
# good: [8bcaa20433634ac70c96d9e5f8ece4b8577c9694] Merge remote-tracking branch 'arm-soc/for-next' into devel-hourly-2013090406
git bisect good 8bcaa20433634ac70c96d9e5f8ece4b8577c9694
# good: [820acdf740b7d04476959189e9a144c2315339a4] drm/i915: do display power state notification on crtc enable/disable
git bisect good 820acdf740b7d04476959189e9a144c2315339a4
# bad: [5bae522a51aa6bbae54bd2d745d0320f74c40b76] Merge remote-tracking branch 'perf/perf/trace.fmt' into devel-hourly-2013090406
git bisect bad 5bae522a51aa6bbae54bd2d745d0320f74c40b76
# bad: [8afb4c018e21c882c8fad196772ef74d494185e2] perf tools: Re-implement debug print function for linking python/perf.so
git bisect bad 8afb4c018e21c882c8fad196772ef74d494185e2
# good: [17f41571bb2c4a398785452ac2718a6c5d77180e] kprobes/x86: Call out into INT3 handler directly instead of using notifier
git bisect good 17f41571bb2c4a398785452ac2718a6c5d77180e
# bad: [34f77abcb34e1da4ee3ca5c5a41b673664eee1fa] perf annotate: Put dso name in symbol annotation title
git bisect bad 34f77abcb34e1da4ee3ca5c5a41b673664eee1fa
# bad: [8404db63461af62025f32f8368861fb33604e62f] perf tests: Add attr record group sampling test
git bisect bad 8404db63461af62025f32f8368861fb33604e62f
# bad: [9a545de019b536771feefb76f85e5038b65c2190] perf: Migrate per cpu event accounting
git bisect bad 9a545de019b536771feefb76f85e5038b65c2190
# good: [62470419e993f8d9d93db0effd3af4296ecb79a5] sched: Implement smarter wake-affine logic
git bisect good 62470419e993f8d9d93db0effd3af4296ecb79a5
# bad: [90983b16078ab0fdc58f0dab3e8e3da79c9579a2] perf: Sanitize get_callchain_buffer()
git bisect bad 90983b16078ab0fdc58f0dab3e8e3da79c9579a2
# bad: [6050cb0b0b366092d1383bc23d7b16cd26db00f0] perf: Fix branch stack refcount leak on callchain init failure
git bisect bad 6050cb0b0b366092d1383bc23d7b16cd26db00f0
# bad: [7d9ffa8961482232d964173cccba6e14d2d543b2] sched: Micro-optimize the smart wake-affine logic
git bisect bad 7d9ffa8961482232d964173cccba6e14d2d543b2
# first bad commit: [7d9ffa8961482232d964173cccba6e14d2d543b2] sched: Micro-optimize the smart wake-affine logic

A comparison of all good commits [*] with all bad commits [o]
(good/bad in the sense of git bisect)

netperf.Throughput_Mbps

208 ++-------------------------------------------------------------------+
206 +OOO O OOO OOOO O O O O O O O |
O O O O OO O O O O O O O O
204 ++ O O O O O OOOO O OOOOO OOO O OO OOO OO|
202 ++ O O |
| O |
200 ++ |
198 ++ |
196 ++ |
| * |
194 ++ ****. *** .**** **.*******.* *** |
192 ++ * * ** :: |
| * *** .* : * |
190 ** *.* **.** **** * |
188 ++------------*------------------------------------------------------+


vmstat.system.in

1640 ++----------O-------------------------------------------------------+
O O OO O O O O |
1620 +O O O O O O O O O O O OO
| O OOO OO OO O O O O O OO O |
1600 ++ O O O O O O OO O O O O |
| O O O O O O O O |
1580 ++ O O O |
| |
1560 ++ * |
| * * * * :* |
1540 ++ * :: ***.* * :**.* ::* * .** :* |
| :+ * * * ** ** ::* * * * * * |
1520 ++* * ::*** +: ** : * |
* : * * :** :: |
1500 +*-------------*----*-----------------------------------------------+


vmstat.system.cs

10000 ++-----------------------------------------------------------------+
*****.***** |
9800 ++ ** .****** |
9600 ++ * :* ** **.* * *** .* * **** |
| * *.** ** ** * * * * *.* |
9400 ++ |
9200 ++ |
| |
9000 ++ |
8800 ++ O |
O O OO O O OOO O O OOO OO OO OO O |
8600 ++O O O O OO OO O O O O OO O O OO O O OO OO
8400 +O O OOO O OO O O OO O O |
| O |
8200 ++-----------------------------------------------------------------+


lock_stat.slock-AF_INET.contentions

110000 ++----------------------------------------------------------------+
| |
105000 ++ O O O O |
OOO O O O O OO O O O O O O O O
| O O O O OOO O O OOOOO O OOO OOO O OOO OOO O|
100000 ++ O O OOO O O O O O |
| O |
95000 ++ |
| |
90000 ++ * * .*** * ** *. * *** *** |
| * ** * * * * * * * ****.* |
| **.* **** ::*. ** : |
85000 *** * * * * * |
| |
80000 ++----------------------------------------------------------------+


lock_stat.slock-AF_INET.contentions.lock_sock_nested

92000 ++-----------------------------------------------------------------+
90000 ++ O O O |
| O O O O O O |
88000 OO O O O OO O O O OO O OO OO O O O OO
86000 ++ O O O OO O OO OO OO O O OOOOOO O |
84000 ++ OO O O O O O O |
82000 ++ O |
| |
80000 ++ |
78000 ++ * *. * * * *. |
76000 ++ * ***.** * * : * * :* **.** *** * * |
74000 ++ **.* * :+ ** : * * * * * |
| * * ***: *** * |
72000 ** * |
70000 ++-----------------------------------------------------------------+


lock_stat.slock-AF_INET.contentions.tcp_v4_rcv

110000 ++----------------------------------------------------------------+
| |
105000 ++ O O O O |
OOO O O O O OO O O O O O O O O
| O O O O OOO O O OOOOO O OOO OOO O OOO OOO O|
100000 ++ O O OOO O O O O O |
| O |
95000 ++ |
| |
90000 ++ * * .*** * ** *. * *** *** |
| * ** * * * * * * * ****.* |
| **.* **** ::*. ** : |
85000 *** * * * * * |
| |
80000 ++----------------------------------------------------------------+

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