Re: drivers/char/random.c: More futzing about

From: George Spelvin
Date: Wed Jun 11 2014 - 23:44:11 EST

Just to add to my total confusion about the totally disparate performance
numbers we're seeing, I did some benchmarks on other machines.

The speedup isn't as good one-pass as it is iterated, and as I mentioned
it's slower on a P4, but it's not 7 times slower by any stretch.

There are all 1-iteration numbers, run immediately after scp-ing the
binary to the machine so there's no possibility if anything being cached.

(The "64" and "32" versions are compiled -m32 and -m64,
of course.)

2.5 GHz Phenom 9850:

$ /tmp/random64
pool 1 = 85670974 e96b1f8f 51244abf 5863283f
pool 2 = 03564c6c eba81d03 55c77fa1 760374a7
0: 199 142 (-57)
1: 104 95 (-9)
2: 104 110 (+6)
3: 103 109 (+6)
4: 105 89 (-16)
5: 103 88 (-15)
6: 104 89 (-15)
7: 104 95 (-9)
8: 105 85 (-20)
9: 105 85 (-20)
$ /tmp/random32
pool 1 = 85670974 e96b1f8f 51244abf 5863283f
pool 2 = 03564c6c eba81d03 55c77fa1 760374a7
0: 324 147 (-177)
1: 100 86 (-14)
2: 100 99 (-1)
3: 100 88 (-12)
4: 100 86 (-14)
5: 100 86 (-14)
6: 100 89 (-11)
7: 100 111 (+11)
8: 100 111 (+11)
9: 100 88 (-12)
$ /tmp/random64 10000
pool 1 = 54b3ba06 4769d67a eb04bbf3 5e42df6e
pool 2 = 9d3c469e 6fecdb60 423af4ca 465173d1
0: 554788 220327 (-334461)
1: 554825 220176 (-334649)
2: 553505 220148 (-333357)
3: 554661 220064 (-334597)
4: 569559 220064 (-349495)
5: 612798 220065 (-392733)
6: 570287 220064 (-350223)
7: 554790 220064 (-334726)
8: 554715 220065 (-334650)
9: 569840 220064 (-349776)
$ /tmp/random32 10000
pool 1 = 54b3ba06 4769d67a eb04bbf3 5e42df6e
pool 2 = 9d3c469e 6fecdb60 423af4ca 465173d1
0: 520117 280225 (-239892)
1: 520125 280154 (-239971)
2: 520104 280094 (-240010)
3: 520079 280060 (-240019)
4: 520069 280060 (-240009)
5: 520060 280060 (-240000)
6: 558971 280060 (-278911)
7: 520102 280060 (-240042)
8: 520082 280060 (-240022)
9: 520058 280060 (-239998)


3 GHz i5-3330:
$ /tmp/random64
pool 1 = 85670974 e96b1f8f 51244abf 5863283f
pool 2 = 03564c6c eba81d03 55c77fa1 760374a7
0: 78 75 (-3)
1: 36 33 (-3)
2: 33 39 (+6)
3: 36 30 (-6)
4: 36 33 (-3)
5: 30 33 (+3)
6: 30 54 (+24)
7: 24 48 (+24)
8: 27 33 (+6)
9: 30 33 (+3)
$ /tmp/random32
pool 1 = 85670974 e96b1f8f 51244abf 5863283f
pool 2 = 03564c6c eba81d03 55c77fa1 760374a7
0: 66 78 (+12)
1: 39 39 (+0)
2: 36 39 (+3)
3: 45 33 (-12)
4: 42 33 (-9)
5: 33 42 (+9)
6: 45 33 (-12)
7: 39 36 (-3)
8: 105 48 (-57)
9: 42 39 (-3)
$ /tmp/random64 10000
pool 1 = 54b3ba06 4769d67a eb04bbf3 5e42df6e
pool 2 = 9d3c469e 6fecdb60 423af4ca 465173d1
0: 406188 218104 (-188084)
1: 402620 246968 (-155652)
2: 402652 239840 (-162812)
3: 402720 200312 (-202408)
4: 402584 200080 (-202504)
5: 447488 200228 (-247260)
6: 402788 200312 (-202476)
7: 402688 200080 (-202608)
8: 427140 224320 (-202820)
9: 402576 200080 (-202496)
$ /tmp/random32 10000
pool 1 = 54b3ba06 4769d67a eb04bbf3 5e42df6e
pool 2 = 9d3c469e 6fecdb60 423af4ca 465173d1
0: 406485 266670 (-139815)
1: 392694 266463 (-126231)
2: 392496 266763 (-125733)
3: 426003 266145 (-159858)
4: 392688 266667 (-126021)
5: 432231 266589 (-165642)
6: 392754 298734 (-94020)
7: 392883 284994 (-107889)
8: 392637 266694 (-125943)
9: 392985 267024 (-125961)


3.5 GHz i7-2700:
# /tmp/perftest /tmp/random64
pool 1 = 85670974 e96b1f8f 51244abf 5863283f
pool 2 = 03564c6c eba81d03 55c77fa1 760374a7
0: 82 90 (+8)
1: 38 41 (+3)
2: 46 38 (-8)
3: 35 41 (+6)
4: 46 41 (-5)
5: 38 38 (+0)
6: 41 55 (+14)
7: 41 35 (-6)
8: 46 24 (-22)
9: 35 38 (+3)
# /tmp/perftest /tmp/random32
pool 1 = 85670974 e96b1f8f 51244abf 5863283f
pool 2 = 03564c6c eba81d03 55c77fa1 760374a7
0: 82 76 (-6)
1: 32 53 (+21)
2: 49 44 (-5)
3: 35 41 (+6)
4: 46 35 (-11)
5: 35 44 (+9)
6: 49 50 (+1)
7: 41 41 (+0)
8: 32 44 (+12)
9: 49 44 (-5)
# /tmp/perftest /tmp/random64 10000
pool 1 = 54b3ba06 4769d67a eb04bbf3 5e42df6e
pool 2 = 9d3c469e 6fecdb60 423af4ca 465173d1
0: 445486 227993 (-217493)
1: 445089 227602 (-217487)
2: 445381 227736 (-217645)
3: 445220 227661 (-217559)
4: 445159 227798 (-217361)
5: 445285 227608 (-217677)
6: 445005 227806 (-217199)
7: 445439 227608 (-217831)
8: 445328 227798 (-217530)
9: 445533 227625 (-217908)
# /tmp/perftest /tmp/random32 10000
pool 1 = 54b3ba06 4769d67a eb04bbf3 5e42df6e
pool 2 = 9d3c469e 6fecdb60 423af4ca 465173d1
0: 437001 335959 (-101042)
1: 437004 336120 (-100884)
2: 436683 335936 (-100747)
3: 436806 336452 (-100354)
4: 436996 335988 (-101008)
5: 436916 336210 (-100706)
6: 437042 354722 (-82320)
7: 436896 336146 (-100750)
8: 436981 336741 (-100240)
9: 437016 331920 (-105096)


And on a 1.6 GHz P4:
$ /tmp/random32
pool 1 = 85670974 e96b1f8f 51244abf 5863283f
pool 2 = 03564c6c eba81d03 55c77fa1 760374a7
0: 312 176 (-136)
1: 112 112 (+0)
2: 112 112 (+0)
3: 112 112 (+0)
4: 112 112 (+0)
5: 112 112 (+0)
6: 112 112 (+0)
7: 112 112 (+0)
8: 112 112 (+0)
9: 112 112 (+0)
$ /tmp/random32 10000
pool 1 = 54b3ba06 4769d67a eb04bbf3 5e42df6e
pool 2 = 9d3c469e 6fecdb60 423af4ca 465173d1
0: 480344 550192 (+69848)
1: 480088 550084 (+69996)
2: 480140 550128 (+69988)
3: 480088 550084 (+69996)
4: 480088 550084 (+69996)
5: 480088 550084 (+69996)
6: 480088 550084 (+69996)
7: 480088 550084 (+69996)
8: 480088 550084 (+69996)
9: 480088 550084 (+69996)


And just for lulz, a 1.533 GHz Athlon XP:
$ /tmp/random32
pool 1 = 85670974 e96b1f8f 51244abf 5863283f
pool 2 = 03564c6c eba81d03 55c77fa1 760374a7
0: 91 83 (-8)
1: 58 57 (-1)
2: 58 57 (-1)
3: 58 57 (-1)
4: 58 45 (-13)
5: 58 45 (-13)
6: 58 45 (-13)
7: 58 45 (-13)
8: 58 45 (-13)
9: 58 45 (-13)
$ /tmp/random32 10000
pool 1 = 54b3ba06 4769d67a eb04bbf3 5e42df6e
pool 2 = 9d3c469e 6fecdb60 423af4ca 465173d1
0: 570094 380159 (-189935)
1: 550045 380088 (-169957)
2: 550028 380043 (-169985)
3: 568533 380087 (-188446)
4: 550028 380021 (-170007)
5: 550028 380021 (-170007)
6: 550028 380021 (-170007)
7: 550028 380021 (-170007)
8: 550028 382985 (-167043)
9: 550088 380021 (-170067)
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