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Re: BufferPainter::Clear() optimization [message #53953 is a reply to message #53952]

Sun, 17 May 2020 20:56

Tom1
Messages: 1212
Registered: March 2007

Senior Contributor

Hi Mirek,

Here are my results:

CLANG

TIMING HUGE memset    : 27.28 ms -  1.36 ms (27.29 ms / 20 ), min:  1.25 ms, max:  1.66 ms, nesting: 0 - 20
TIMING HUGE Fill3     : 35.01 ms -  1.75 ms (35.01 ms / 20 ), min:  1.63 ms, max:  1.99 ms, nesting: 0 - 20
TIMING HUGE Fill      : 73.74 ms -  3.69 ms (73.75 ms / 20 ), min:  3.32 ms, max:  7.43 ms, nesting: 0 - 20
TIMING HUGE memsetd   : 72.88 ms -  3.64 ms (72.88 ms / 20 ), min:  3.40 ms, max:  4.51 ms, nesting: 0 - 20
TIMING memset         :  1.01 s  -  1.01 us ( 1.07 s  / 1000000 ), min:  1.00 us, max: 28.00 us, nesting: 0 - 1000000
TIMING Fill3          : 505.44 ms - 505.44 ns (565.98 ms / 1000000 ), min:  0.00 ns, max: 29.00 us, nesting: 0 - 1000000
TIMING Fill2          : 497.06 ms - 497.06 ns (557.61 ms / 1000000 ), min:  0.00 ns, max: 28.00 us, nesting: 0 - 1000000
TIMING Fill0          : 772.53 ms - 772.53 ns (833.07 ms / 1000000 ), min:  0.00 ns, max: 63.00 us, nesting: 0 - 1000000
TIMING Fill           :  1.67 s  -  1.67 us ( 1.73 s  / 1000000 ), min:  1.00 us, max: 58.00 us, nesting: 0 - 1000000
TIMING memsetd        : 495.67 ms - 495.67 ns (556.22 ms / 1000000 ), min:  0.00 ns, max: 28.00 us, nesting: 0 - 1000000

CLANGx64

TIMING HUGE memset    : 27.76 ms -  1.39 ms (27.76 ms / 20 ), min:  1.28 ms, max:  1.80 ms, nesting: 0 - 20
TIMING HUGE Fill3     : 36.31 ms -  1.82 ms (36.31 ms / 20 ), min:  1.59 ms, max:  2.27 ms, nesting: 0 - 20
TIMING HUGE Fill      : 73.42 ms -  3.67 ms (73.42 ms / 20 ), min:  3.41 ms, max:  4.74 ms, nesting: 0 - 20
TIMING HUGE memsetd   : 74.52 ms -  3.73 ms (74.52 ms / 20 ), min:  3.47 ms, max:  4.22 ms, nesting: 0 - 20
TIMING memset         : 898.49 ms - 898.49 ns (925.83 ms / 1000000 ), min:  0.00 ns, max: 52.00 us, nesting: 0 - 1000000
TIMING Fill3          : 492.59 ms - 492.59 ns (519.92 ms / 1000000 ), min:  0.00 ns, max: 32.00 us, nesting: 0 - 1000000
TIMING Fill2          : 495.82 ms - 495.82 ns (523.15 ms / 1000000 ), min:  0.00 ns, max: 28.00 us, nesting: 0 - 1000000
TIMING Fill0          : 569.61 ms - 569.61 ns (596.95 ms / 1000000 ), min:  0.00 ns, max: 41.00 us, nesting: 0 - 1000000
TIMING Fill           : 591.56 ms - 591.56 ns (618.90 ms / 1000000 ), min:  0.00 ns, max: 30.00 us, nesting: 0 - 1000000
TIMING memsetd        : 549.04 ms - 549.04 ns (576.37 ms / 1000000 ), min:  0.00 ns, max: 65.00 us, nesting: 0 - 1000000

MSBT19

TIMING HUGE memset    : 26.51 ms -  1.33 ms (26.51 ms / 20 ), min:  1.26 ms, max:  1.49 ms, nesting: 0 - 20
TIMING HUGE Fill3     : 35.42 ms -  1.77 ms (35.42 ms / 20 ), min:  1.58 ms, max:  2.14 ms, nesting: 0 - 20
TIMING HUGE Fill      : 25.47 ms -  1.27 ms (25.48 ms / 20 ), min:  1.18 ms, max:  1.59 ms, nesting: 0 - 20
TIMING HUGE memsetd   : 25.12 ms -  1.26 ms (25.12 ms / 20 ), min:  1.15 ms, max:  1.59 ms, nesting: 0 - 20
TIMING memset         : 978.21 ms - 978.21 ns ( 1.05 s  / 1000000 ), min:  1.00 us, max: 29.00 us, nesting: 0 - 1000000
TIMING Fill3          :  1.50 s  -  1.50 us ( 1.58 s  / 1000000 ), min:  1.00 us, max: 29.00 us, nesting: 0 - 1000000
TIMING Fill2          :  1.89 s  -  1.89 us ( 1.96 s  / 1000000 ), min:  1.00 us, max: 34.00 us, nesting: 0 - 1000000
TIMING Fill0          :  2.02 s  -  2.02 us ( 2.09 s  / 1000000 ), min:  1.00 us, max: 33.00 us, nesting: 0 - 1000000
TIMING Fill           :  2.06 s  -  2.06 us ( 2.14 s  / 1000000 ), min:  1.00 us, max: 32.00 us, nesting: 0 - 1000000
TIMING memsetd        :  1.62 s  -  1.62 us ( 1.69 s  / 1000000 ), min:  1.00 us, max: 45.00 us, nesting: 0 - 1000000

MSBT19x64

TIMING HUGE memset    : 26.96 ms -  1.35 ms (26.96 ms / 20 ), min:  1.27 ms, max:  1.90 ms, nesting: 0 - 20
TIMING HUGE Fill3     : 35.07 ms -  1.75 ms (35.08 ms / 20 ), min:  1.62 ms, max:  2.02 ms, nesting: 0 - 20
TIMING HUGE Fill      : 67.09 ms -  3.35 ms (67.09 ms / 20 ), min:  3.17 ms, max:  3.60 ms, nesting: 0 - 20
TIMING HUGE memsetd   : 25.64 ms -  1.28 ms (25.64 ms / 20 ), min:  1.19 ms, max:  1.48 ms, nesting: 0 - 20
TIMING memset         : 818.75 ms - 818.75 ns (856.11 ms / 1000000 ), min:  0.00 ns, max: 31.00 us, nesting: 0 - 1000000
TIMING Fill3          :  1.36 s  -  1.36 us ( 1.40 s  / 1000000 ), min:  1.00 us, max: 31.00 us, nesting: 0 - 1000000
TIMING Fill2          :  1.67 s  -  1.67 us ( 1.70 s  / 1000000 ), min:  1.00 us, max: 30.00 us, nesting: 0 - 1000000
TIMING Fill0          :  1.66 s  -  1.66 us ( 1.70 s  / 1000000 ), min:  1.00 us, max: 46.00 us, nesting: 0 - 1000000
TIMING Fill           :  1.68 s  -  1.68 us ( 1.72 s  / 1000000 ), min:  1.00 us, max: 50.00 us, nesting: 0 - 1000000
TIMING memsetd        :  1.50 s  -  1.50 us ( 1.54 s  / 1000000 ), min:  1.00 us, max: 29.00 us, nesting: 0 - 1000000

Fill3 is generally the best, but I experience two issues behind the scenes of this benchmark:

1. On MSBT19 / MSBT19x64 there is a significant penalty for small counts. It results in 5 ns per call, whereas in CLANG it is about 0.8 - 1.0 ns per call.
2. On MSBT19x64 the optimal threshold size is 2M counts on my Core i7. However, interestingly the default threshold value works better with MSBT19 on the same computer.

I will continue to investigate this.

Thanks and best regards,

Tom

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