Patchwork D9302: copies-rust: leverage the immutability for efficient update

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Submitter phabricator
Date Nov. 12, 2020, 3:16 p.m.
Message ID <differential-rev-PHID-DREV-ywoeinwyqgeg3qo77gx7-req@mercurial-scm.org>
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Permalink /patch/47577/
State Superseded
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phabricator - Nov. 12, 2020, 3:16 p.m.
marmoute created this revision.
Herald added a reviewer: hg-reviewers.
Herald added a subscriber: mercurial-patches.

REVISION SUMMARY
  The immutable OrdMap has a diff function. That function yield items for each
  difference (missing in minor, missing in major or present in both, but
  different). We reorganise the manifest merging code to use this new function.
  We gather the data we would need to inject into the `minor` or `major` dict and
  eventually update one of them. The semantic of the merge itself is kept as is.
  
  Why are we doing this? Last year we contributed a patch that makes a common
  ancestors, that diff function quickly detect some of the identical subsection
  when comparing two OrdMap cloned from the ancestors (because they point to the
  very same node in memory).
  
  As a result:
  
  - That diff function is very fast in most of our cases,
  - It is important to minimise the amount of unnecessary changes we do in theses Map, to maximize the "common" part. This is why we gather update for both and update the one with the smaller update.
  
  In practice, this yield a massive speed up on all our slow cases. Some example
  below.
  
  Repo            Cases                                 Source-Rev   Dest-Rev         Old-Time      New-Time     Difference   Factor
  ----------------------------------------------------------------------------------------------------------------------------------
  
  pypy            x0000_revs_x_added_0_copies           d1defd0dc478 c9cb1334cc78 :  33.527067 s,   2.780174 s, -30.746893 s, × 0.0829
  netbeans        x0000_revs_xx000_added_x000_copies    588c2d1ced70 1aad62e59ddd : killed(>120),   1.231869 s
  mozilla-central x00000_revs_x0000_added_x0000_copies  6832ae71433c 4c222a1d9a00 : killed(>120),   3.478747 s
  mozilla-try     x0000_revs_xx000_added_x000_copies    89294cd501d9 7ccb2fc7ccb5 :  83.508590 s,   9.843481 s, -73.665109 s, × 0.1179
  mozilla-try     x0000_revs_x0000_added_x0000_copies   e928c65095ed e951f4ad123a :  55.079813 s,   1.465128 s, -53.614685 s, × 0.0266
  
  The performance compared to the Python code are now comparable (worst case are a
  score percent slower)" You an check the full table below for details.
  
  The big new is that, with this change, we are now faster filelog in most case, .
  Below is an highlight of some pretty nice win:
  
  Repo            Case                                  Source-Rev   Dest-Rev         filelog     sidedata      Difference       Factor
  -------------------------------------------------------------------------------------------------------------------------------------
  
  pypy            x0000_revs_xx000_added_x000_copies    08ea3258278e d9fa043f30c0 :  1.354211 s, 0.252125 s, -1.102086 s, × 0.186179
  netbeans        x000_revs_x000_added_x000_copies      ff453e9fee32 411350406ec2 :  0.939593 s, 0.112534 s, -0.827059 s, × 0.119769
  netbeans        x0000_revs_xx000_added_x000_copies    588c2d1ced70 1aad62e59ddd :  3.824967 s, 1.231869 s, -2.593098 s, × 0.322060
  mozilla-central x000_revs_x000_added_x000_copies      7c97034feb78 4407bd0c6330 :  1.142414 s, 0.102184 s, -1.040230 s, × 0.089446
  mozilla-central x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :  6.667504 s, 0.046220 s, -6.621284 s, × 0.006932
  mozilla-central x0000_revs_xx000_added_x000_copies    f78c615a656c 96a38b690156 :  3.267274 s, 0.315271 s, -2.952003 s, × 0.096494
  mozilla-central x00000_revs_x0000_added_x0000_copies  6832ae71433c 4c222a1d9a00 : 16.038104 s, 3.478747 s, -12.559357 s, × 0.216905
  mozilla-central x00000_revs_x00000_added_x000_copies  76caed42cf7c 1daa622bbe42 : 20.639928 s, 4.766435 s, -15.873493 s, × 0.230933
  
  They they are a handful of slower case where we perform less well. A good Share
  of them are really pathological "service" merge in mozilla-try, but not all of
  them.
  
  Repo            Case                                  Source-Rev   Dest-Rev         filelog     sidedata      Difference       Factor
  -------------------------------------------------------------------------------------------------------------------------------------
  
  pypy            x0000_revs_x_added_0_copies           d1defd0dc478 c9cb1334cc78 :  0.001055 s, 2.780174 s, +2.779119 s, × 2635.236019
  mozilla-try     x0000_revs_x_added_0_copies           63519bfd42ee a36a2a865d92 : 0.088715 s, 0.435381 s, +0.346666 s, × 4.907637
  mozilla-try     x0000_revs_x_added_x_copies           9fe69ff0762d bcabf2a78927 : 0.080765 s, 0.415461 s, +0.334696 s, × 5.144072
  mozilla-try     x0000_revs_xx000_added_x000_copies    89294cd501d9 7ccb2fc7ccb5 : 7.598509 s, 9.843481 s, +2.244972 s, × 1.295449
  mozilla-try     x00000_revs_x_added_0_copies          6a320851d377 1ebb79acd503 : 0.092232 s, killed
  mozilla-try     x00000_revs_x_added_x_copies          5173c4b6f97c 95d83ee7242d : 0.093892 s, killed
  mozilla-try     x00000_revs_x000_added_x_copies       9126823d0e9c ca82787bb23c : 0.227503 s, killed
  mozilla-try     x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 21.145391 s, killed
  mozilla-try     x00000_revs_x00000_added_x000_copies  9b2a99adc05e 8e29777b48e6 : 25.304164 s, killed
  
  Below are two different tables for full performance comparison
  
  - this changeset against the previous one (spoiler: it is much better)
  - this changeset against the python code  (spoiler: still slower, but it gets more comparable)
  - this changeset against the filelog code (spoiler: better in many case, but not all)
  
  Repo            Cases                                 Source-Rev   Dest-Rev         Old-Time      New-Time     Difference   Factor
  ----------------------------------------------------------------------------------------------------------------------------------
  
  mercurial       x_revs_x_added_0_copies               ad6b123de1c7 <https://phab.mercurial-scm.org/rHGad6b123de1c7868a4be537a0e3fa5eb6a962dd3b> 39cfcef4f463 <https://phab.mercurial-scm.org/rHG39cfcef4f46358a25ebf32670191687826ca2bdf> :   0.000049 s,   0.000049 s,  +0.000000 s, × 1.0000
  mercurial       x_revs_x_added_x_copies               2b1c78674230 <https://phab.mercurial-scm.org/rHG2b1c786742301bb757226a898fafe595a90462fb> 0c1d10351869 <https://phab.mercurial-scm.org/rHG0c1d103518698454c9a8825b66276becf2820f86> :   0.000179 s,   0.000182 s,  +0.000003 s, × 1.0168
  mercurial       x000_revs_x000_added_x_copies         81f8ff2a9bf2 <https://phab.mercurial-scm.org/rHG81f8ff2a9bf20606fc89bc787983f592183e25b5> dd3267698d84 <https://phab.mercurial-scm.org/rHGdd3267698d84458686b3c5682ce027438900ffbd> :   0.006494 s,   0.005872 s,  -0.000622 s, × 0.9042
  pypy            x_revs_x_added_0_copies               aed021ee8ae8 099ed31b181b :   0.000339 s,   0.000229 s,  -0.000110 s, × 0.6755
  pypy            x_revs_x000_added_0_copies            4aa4e1f8e19a 359343b9ac0e :   0.000057 s,   0.000058 s,  +0.000001 s, × 1.0175
  pypy            x_revs_x_added_x_copies               ac52eb7bbbb0 72e022663155 :   0.000299 s,   0.000148 s,  -0.000151 s, × 0.4950
  pypy            x_revs_x00_added_x_copies             c3b14617fbd7 ace7255d9a26 :   0.001200 s,   0.001205 s,  +0.000005 s, × 1.0042
  pypy            x_revs_x000_added_x000_copies         df6f7a526b60 a83dc6a2d56f :   0.025120 s,   0.025662 s,  +0.000542 s, × 1.0216
  pypy            x000_revs_xx00_added_0_copies         89a76aede314 2f22446ff07e :   0.506921 s,   0.080113 s,  -0.426808 s, × 0.1580
  pypy            x000_revs_x000_added_x_copies         8a3b5bfd266e 2c68e87c3efe :   1.272060 s,   0.153030 s,  -1.119030 s, × 0.1203
  pypy            x000_revs_x000_added_x000_copies      89a76aede314 7b3dda341c84 :   0.690941 s,   0.098774 s,  -0.592167 s, × 0.1430
  pypy            x0000_revs_x_added_0_copies           d1defd0dc478 c9cb1334cc78 :  33.527067 s,   2.780174 s, -30.746893 s, × 0.0829
  pypy            x0000_revs_xx000_added_0_copies       bf2c629d0071 4ffed77c095c :   0.021970 s,   0.022218 s,  +0.000248 s, × 1.0113
  pypy            x0000_revs_xx000_added_x000_copies    08ea3258278e d9fa043f30c0 :   1.772094 s,   0.252125 s,  -1.519969 s, × 0.1423
  netbeans        x_revs_x_added_0_copies               fb0955ffcbcd a01e9239f9e7 :   0.000185 s,   0.000186 s,  +0.000001 s, × 1.0054
  netbeans        x_revs_x000_added_0_copies            6f360122949f 20eb231cc7d0 :   0.000135 s,   0.000133 s,  -0.000002 s, × 0.9852
  netbeans        x_revs_x_added_x_copies               1ada3faf6fb6 5a39d12eecf4 :   0.000329 s,   0.000320 s,  -0.000009 s, × 0.9726
  netbeans        x_revs_x00_added_x_copies             35be93ba1e2c 9eec5e90c05f :   0.001343 s,   0.001336 s,  -0.000007 s, × 0.9948
  netbeans        x000_revs_xx00_added_0_copies         eac3045b4fdd 51d4ae7f1290 :   0.029396 s,   0.015573 s,  -0.013823 s, × 0.5298
  netbeans        x000_revs_x000_added_x_copies         e2063d266acd 6081d72689dc :   0.040210 s,   0.018667 s,  -0.021543 s, × 0.4642
  netbeans        x000_revs_x000_added_x000_copies      ff453e9fee32 411350406ec2 :   4.556794 s,   0.112534 s,  -4.444260 s, × 0.0247
  netbeans        x0000_revs_xx000_added_x000_copies    588c2d1ced70 1aad62e59ddd : killed      ,   1.231869 s
  mozilla-central x_revs_x_added_0_copies               3697f962bb7b 7015fcdd43a2 :   0.000199 s,   0.000197 s,  -0.000002 s, × 0.9899
  mozilla-central x_revs_x000_added_0_copies            dd390860c6c9 40d0c5bed75d :   0.000639 s,   0.000637 s,  -0.000002 s, × 0.9969
  mozilla-central x_revs_x_added_x_copies               8d198483ae3b 14207ffc2b2f :   0.000542 s,   0.000303 s,  -0.000239 s, × 0.5590
  mozilla-central x_revs_x00_added_x_copies             98cbc58cc6bc 446a150332c3 :   0.001685 s,   0.001663 s,  -0.000022 s, × 0.9869
  mozilla-central x_revs_x000_added_x000_copies         3c684b4b8f68 0a5e72d1b479 :   0.006954 s,   0.007008 s,  +0.000054 s, × 1.0078
  mozilla-central x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :   0.132938 s,   0.127385 s,  -0.005553 s, × 0.9582
  mozilla-central x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   0.008683 s,   0.008740 s,  +0.000057 s, × 1.0066
  mozilla-central x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :   0.005956 s,   0.005783 s,  -0.000173 s, × 0.9710
  mozilla-central x000_revs_x000_added_x000_copies      7c97034feb78 4407bd0c6330 :   0.963905 s,   0.102184 s,  -0.861721 s, × 0.1060
  mozilla-central x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :   0.049239 s,   0.046220 s,  -0.003019 s, × 0.9387
  mozilla-central x0000_revs_xx000_added_x000_copies    f78c615a656c 96a38b690156 :   4.217003 s,   0.315271 s,  -3.901732 s, × 0.0748
  mozilla-central x00000_revs_x0000_added_x0000_copies  6832ae71433c 4c222a1d9a00 : killed      ,   3.478747 s
  mozilla-central x00000_revs_x00000_added_x000_copies  76caed42cf7c 1daa622bbe42 : killed      ,   4.766435 s
  mozilla-try     x_revs_x_added_0_copies               aaf6dde0deb8 9790f499805a :   0.001197 s,   0.001214 s,  +0.000017 s, × 1.0142
  mozilla-try     x_revs_x000_added_0_copies            d8d0222927b4 5bb8ce8c7450 :   0.001213 s,   0.001221 s,  +0.000008 s, × 1.0066
  mozilla-try     x_revs_x_added_x_copies               092fcca11bdb 936255a0384a :   0.000762 s,   0.000613 s,  -0.000149 s, × 0.8045
  mozilla-try     x_revs_x00_added_x_copies             b53d2fadbdb5 017afae788ec :   0.001909 s,   0.001904 s,  -0.000005 s, × 0.9974
  mozilla-try     x_revs_x000_added_x000_copies         20408ad61ce5 6f0ee96e21ad :   0.093021 s,   0.093000 s,  -0.000021 s, × 0.9998
  mozilla-try     x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :   0.134536 s,   0.132194 s,  -0.002342 s, × 0.9826
  mozilla-try     x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   0.009071 s,   0.009069 s,  -0.000002 s, × 0.9998
  mozilla-try     x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :   0.006206 s,   0.006169 s,  -0.000037 s, × 0.9940
  mozilla-try     x000_revs_x000_added_x000_copies      1346fd0130e4 4c65cbdabc1f :   1.150502 s,   0.115540 s,  -1.034962 s, × 0.1004
  mozilla-try     x0000_revs_x_added_0_copies           63519bfd42ee a36a2a865d92 :   1.114864 s,   0.435381 s,  -0.679483 s, × 0.3905
  mozilla-try     x0000_revs_x_added_x_copies           9fe69ff0762d bcabf2a78927 :   1.042658 s,   0.415461 s,  -0.627197 s, × 0.3985
  mozilla-try     x0000_revs_xx000_added_x_copies       156f6e2674f2 4d0f2c178e66 :   0.447402 s,   0.155946 s,  -0.291456 s, × 0.3486
  mozilla-try     x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :   0.051132 s,   0.048521 s,  -0.002611 s, × 0.9489
  mozilla-try     x0000_revs_xx000_added_x000_copies    89294cd501d9 7ccb2fc7ccb5 :  83.508590 s,   9.843481 s, -73.665109 s, × 0.1179
  mozilla-try     x0000_revs_x0000_added_x0000_copies   e928c65095ed e951f4ad123a :  55.079813 s,   1.465128 s, -53.614685 s, × 0.0266
  mozilla-try     x00000_revs_x00000_added_0_copies     dc8a3ca7010e d16fde900c9c :   1.442793 s,   1.374283 s,  -0.068510 s, × 0.9525
  mozilla-try     x00000_revs_x0000_added_x0000_copies  8d3fafa80d4b eb884023b810 : killed      ,   5.255158 s
  
  Repo            Cases                                 Source-Rev   Dest-Rev         Py-time       Rust-time    Difference   Factor
  ----------------------------------------------------------------------------------------------------------------------------------
  
  mercurial       x_revs_x_added_0_copies               ad6b123de1c7 <https://phab.mercurial-scm.org/rHGad6b123de1c7868a4be537a0e3fa5eb6a962dd3b> 39cfcef4f463 <https://phab.mercurial-scm.org/rHG39cfcef4f46358a25ebf32670191687826ca2bdf> :   0.000044 s,   0.000049 s,  +0.000005 s, × 1.1136
  mercurial       x_revs_x_added_x_copies               2b1c78674230 <https://phab.mercurial-scm.org/rHG2b1c786742301bb757226a898fafe595a90462fb> 0c1d10351869 <https://phab.mercurial-scm.org/rHG0c1d103518698454c9a8825b66276becf2820f86> :   0.000138 s,   0.000182 s,  +0.000044 s, × 1.3188
  mercurial       x000_revs_x000_added_x_copies         81f8ff2a9bf2 <https://phab.mercurial-scm.org/rHG81f8ff2a9bf20606fc89bc787983f592183e25b5> dd3267698d84 <https://phab.mercurial-scm.org/rHGdd3267698d84458686b3c5682ce027438900ffbd> :   0.005052 s,   0.005872 s,  +0.000820 s, × 1.1623
  pypy            x_revs_x_added_0_copies               aed021ee8ae8 099ed31b181b :   0.000219 s,   0.000229 s,  +0.000010 s, × 1.0457
  pypy            x_revs_x000_added_0_copies            4aa4e1f8e19a 359343b9ac0e :   0.000055 s,   0.000058 s,  +0.000003 s, × 1.0545
  pypy            x_revs_x_added_x_copies               ac52eb7bbbb0 72e022663155 :   0.000128 s,   0.000148 s,  +0.000020 s, × 1.1562
  pypy            x_revs_x00_added_x_copies             c3b14617fbd7 ace7255d9a26 :   0.001089 s,   0.001205 s,  +0.000116 s, × 1.1065
  pypy            x_revs_x000_added_x000_copies         df6f7a526b60 a83dc6a2d56f :   0.017407 s,   0.025662 s,  +0.008255 s, × 1.4742
  pypy            x000_revs_xx00_added_0_copies         89a76aede314 2f22446ff07e :   0.094175 s,   0.080113 s,  -0.014062 s, × 0.8507
  pypy            x000_revs_x000_added_x_copies         8a3b5bfd266e 2c68e87c3efe :   0.238009 s,   0.153030 s,  -0.084979 s, × 0.6430
  pypy            x000_revs_x000_added_x000_copies      89a76aede314 7b3dda341c84 :   0.125876 s,   0.098774 s,  -0.027102 s, × 0.7847
  pypy            x0000_revs_x_added_0_copies           d1defd0dc478 c9cb1334cc78 :   3.581556 s,   2.780174 s,  -0.801382 s, × 0.7762
  pypy            x0000_revs_xx000_added_0_copies       bf2c629d0071 4ffed77c095c :   0.016721 s,   0.022218 s,  +0.005497 s, × 1.3287
  pypy            x0000_revs_xx000_added_x000_copies    08ea3258278e d9fa043f30c0 :   0.242367 s,   0.252125 s,  +0.009758 s, × 1.0403
  netbeans        x_revs_x_added_0_copies               fb0955ffcbcd a01e9239f9e7 :   0.000165 s,   0.000186 s,  +0.000021 s, × 1.1273
  netbeans        x_revs_x000_added_0_copies            6f360122949f 20eb231cc7d0 :   0.000114 s,   0.000133 s,  +0.000019 s, × 1.1667
  netbeans        x_revs_x_added_x_copies               1ada3faf6fb6 5a39d12eecf4 :   0.000296 s,   0.000320 s,  +0.000024 s, × 1.0811
  netbeans        x_revs_x00_added_x_copies             35be93ba1e2c 9eec5e90c05f :   0.001124 s,   0.001336 s,  +0.000212 s, × 1.1886
  netbeans        x000_revs_xx00_added_0_copies         eac3045b4fdd 51d4ae7f1290 :   0.013060 s,   0.015573 s,  +0.002513 s, × 1.1924
  netbeans        x000_revs_x000_added_x_copies         e2063d266acd 6081d72689dc :   0.017112 s,   0.018667 s,  +0.001555 s, × 1.0909
  netbeans        x000_revs_x000_added_x000_copies      ff453e9fee32 411350406ec2 :   0.660350 s,   0.112534 s,  -0.547816 s, × 0.1704
  netbeans        x0000_revs_xx000_added_x000_copies    588c2d1ced70 1aad62e59ddd :  10.032499 s,   1.231869 s,  -8.800630 s, × 0.1228
  mozilla-central x_revs_x_added_0_copies               3697f962bb7b 7015fcdd43a2 :   0.000189 s,   0.000197 s,  +0.000008 s, × 1.0423
  mozilla-central x_revs_x000_added_0_copies            dd390860c6c9 40d0c5bed75d :   0.000462 s,   0.000637 s,  +0.000175 s, × 1.3788
  mozilla-central x_revs_x_added_x_copies               8d198483ae3b 14207ffc2b2f :   0.000270 s,   0.000303 s,  +0.000033 s, × 1.1222
  mozilla-central x_revs_x00_added_x_copies             98cbc58cc6bc 446a150332c3 :   0.001474 s,   0.001663 s,  +0.000189 s, × 1.1282
  mozilla-central x_revs_x000_added_x000_copies         3c684b4b8f68 0a5e72d1b479 :   0.004806 s,   0.007008 s,  +0.002202 s, × 1.4582
  mozilla-central x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :   0.085150 s,   0.127385 s,  +0.042235 s, × 1.4960
  mozilla-central x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   0.007064 s,   0.008740 s,  +0.001676 s, × 1.2373
  mozilla-central x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :   0.004741 s,   0.005783 s,  +0.001042 s, × 1.2198
  mozilla-central x000_revs_x000_added_x000_copies      7c97034feb78 4407bd0c6330 :   0.190133 s,   0.102184 s,  -0.087949 s, × 0.5374
  mozilla-central x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :   0.035651 s,   0.046220 s,  +0.010569 s, × 1.2965
  mozilla-central x0000_revs_xx000_added_x000_copies    f78c615a656c 96a38b690156 :   0.440694 s,   0.315271 s,  -0.125423 s, × 0.7154
  mozilla-central x00000_revs_x0000_added_x0000_copies  6832ae71433c 4c222a1d9a00 :  18.454163 s,   3.478747 s, -14.975416 s, × 0.1885
  mozilla-central x00000_revs_x00000_added_x000_copies  76caed42cf7c 1daa622bbe42 :  31.562719 s,   4.766435 s, -26.796284 s, × 0.1510
  mozilla-try     x_revs_x_added_0_copies               aaf6dde0deb8 9790f499805a :   0.001189 s,   0.001214 s,  +0.000025 s, × 1.0210
  mozilla-try     x_revs_x000_added_0_copies            d8d0222927b4 5bb8ce8c7450 :   0.001204 s,   0.001221 s,  +0.000017 s, × 1.0141
  mozilla-try     x_revs_x_added_x_copies               092fcca11bdb 936255a0384a :   0.000586 s,   0.000613 s,  +0.000027 s, × 1.0461
  mozilla-try     x_revs_x00_added_x_copies             b53d2fadbdb5 017afae788ec :   0.001845 s,   0.001904 s,  +0.000059 s, × 1.0320
  mozilla-try     x_revs_x000_added_x000_copies         20408ad61ce5 6f0ee96e21ad :   0.063822 s,   0.093000 s,  +0.029178 s, × 1.4572
  mozilla-try     x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :   0.088038 s,   0.132194 s,  +0.044156 s, × 1.5016
  mozilla-try     x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :   0.007389 s,   0.009069 s,  +0.001680 s, × 1.2274
  mozilla-try     x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :   0.004868 s,   0.006169 s,  +0.001301 s, × 1.2673
  mozilla-try     x000_revs_x000_added_x000_copies      1346fd0130e4 4c65cbdabc1f :   0.222450 s,   0.115540 s,  -0.106910 s, × 0.5194
  mozilla-try     x0000_revs_x_added_0_copies           63519bfd42ee a36a2a865d92 :   0.370675 s,   0.435381 s,  +0.064706 s, × 1.1746
  mozilla-try     x0000_revs_x_added_x_copies           9fe69ff0762d bcabf2a78927 :   0.358020 s,   0.415461 s,  +0.057441 s, × 1.1604
  mozilla-try     x0000_revs_xx000_added_x_copies       156f6e2674f2 4d0f2c178e66 :   0.145235 s,   0.155946 s,  +0.010711 s, × 1.0737
  mozilla-try     x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :   0.037606 s,   0.048521 s,  +0.010915 s, × 1.2902
  mozilla-try     x0000_revs_xx000_added_x000_copies    89294cd501d9 7ccb2fc7ccb5 :   7.382439 s,   9.843481 s,  +2.461042 s, × 1.3334
  mozilla-try     x0000_revs_x0000_added_x0000_copies   e928c65095ed e951f4ad123a :   7.273506 s,   1.465128 s,  -5.808378 s, × 0.2014
  mozilla-try     x00000_revs_x00000_added_0_copies     dc8a3ca7010e d16fde900c9c :   1.074593 s,   1.374283 s,  +0.299690 s, × 1.2789
  mozilla-try     x00000_revs_x0000_added_x0000_copies  8d3fafa80d4b eb884023b810 :  27.746195 s,   5.255158 s, -22.491037 s, × 0.1894
  
  Repo            Case                                  Source-Rev   Dest-Rev         filelog     sidedata      Difference       Factor
  -------------------------------------------------------------------------------------------------------------------------------------
  
  mercurial       x_revs_x_added_0_copies               ad6b123de1c7 <https://phab.mercurial-scm.org/rHGad6b123de1c7868a4be537a0e3fa5eb6a962dd3b> 39cfcef4f463 <https://phab.mercurial-scm.org/rHG39cfcef4f46358a25ebf32670191687826ca2bdf> :  0.000906 s, 0.000049 s, -0.000857 s, × 0.054084
  mercurial       x_revs_x_added_x_copies               2b1c78674230 <https://phab.mercurial-scm.org/rHG2b1c786742301bb757226a898fafe595a90462fb> 0c1d10351869 <https://phab.mercurial-scm.org/rHG0c1d103518698454c9a8825b66276becf2820f86> :  0.001832 s, 0.000182 s, -0.001650 s, × 0.099345
  mercurial       x000_revs_x000_added_x_copies         81f8ff2a9bf2 <https://phab.mercurial-scm.org/rHG81f8ff2a9bf20606fc89bc787983f592183e25b5> dd3267698d84 <https://phab.mercurial-scm.org/rHGdd3267698d84458686b3c5682ce027438900ffbd> :  0.018101 s, 0.005872 s, -0.012229 s, × 0.324402
  pypy            x_revs_x_added_0_copies               aed021ee8ae8 099ed31b181b :  0.001508 s, 0.000229 s, -0.001279 s, × 0.151857
  pypy            x_revs_x000_added_0_copies            4aa4e1f8e19a 359343b9ac0e :  0.207438 s, 0.000058 s, -0.207380 s, × 0.000280
  pypy            x_revs_x_added_x_copies               ac52eb7bbbb0 72e022663155 :  0.016956 s, 0.000148 s, -0.016808 s, × 0.008728
  pypy            x_revs_x00_added_x_copies             c3b14617fbd7 ace7255d9a26 :  0.019129 s, 0.001205 s, -0.017924 s, × 0.062993
  pypy            x_revs_x000_added_x000_copies         df6f7a526b60 a83dc6a2d56f :  0.772050 s, 0.025662 s, -0.746388 s, × 0.033239
  pypy            x000_revs_xx00_added_0_copies         89a76aede314 2f22446ff07e :  1.181775 s, 0.080113 s, -1.101662 s, × 0.067790
  pypy            x000_revs_x000_added_x_copies         8a3b5bfd266e 2c68e87c3efe :  1.255717 s, 0.153030 s, -1.102687 s, × 0.121867
  pypy            x000_revs_x000_added_x000_copies      89a76aede314 7b3dda341c84 :  1.628132 s, 0.098774 s, -1.529358 s, × 0.060667
  pypy            x0000_revs_x_added_0_copies           d1defd0dc478 c9cb1334cc78 :  0.001055 s, 2.780174 s, +2.779119 s, × 2635.236019
  pypy            x0000_revs_xx000_added_0_copies       bf2c629d0071 4ffed77c095c :  1.056756 s, 0.022218 s, -1.034538 s, × 0.021025
  pypy            x0000_revs_xx000_added_x000_copies    08ea3258278e d9fa043f30c0 :  1.354211 s, 0.252125 s, -1.102086 s, × 0.186179
  netbeans        x_revs_x_added_0_copies               fb0955ffcbcd a01e9239f9e7 :  0.027759 s, 0.000186 s, -0.027573 s, × 0.006701
  netbeans        x_revs_x000_added_0_copies            6f360122949f 20eb231cc7d0 :  0.133382 s, 0.000133 s, -0.133249 s, × 0.000997
  netbeans        x_revs_x_added_x_copies               1ada3faf6fb6 5a39d12eecf4 :  0.025353 s, 0.000320 s, -0.025033 s, × 0.012622
  netbeans        x_revs_x00_added_x_copies             35be93ba1e2c 9eec5e90c05f :  0.052939 s, 0.001336 s, -0.051603 s, × 0.025237
  netbeans        x000_revs_xx00_added_0_copies         eac3045b4fdd 51d4ae7f1290 :  0.037532 s, 0.015573 s, -0.021959 s, × 0.414926
  netbeans        x000_revs_x000_added_x_copies         e2063d266acd 6081d72689dc :  0.195401 s, 0.018667 s, -0.176734 s, × 0.095532
  netbeans        x000_revs_x000_added_x000_copies      ff453e9fee32 411350406ec2 :  0.939593 s, 0.112534 s, -0.827059 s, × 0.119769
  netbeans        x0000_revs_xx000_added_x000_copies    588c2d1ced70 1aad62e59ddd :  3.824967 s, 1.231869 s, -2.593098 s, × 0.322060
  mozilla-central x_revs_x_added_0_copies               3697f962bb7b 7015fcdd43a2 :  0.024626 s, 0.000197 s, -0.024429 s, × 0.008000
  mozilla-central x_revs_x000_added_0_copies            dd390860c6c9 40d0c5bed75d :  0.141098 s, 0.000637 s, -0.140461 s, × 0.004515
  mozilla-central x_revs_x_added_x_copies               8d198483ae3b 14207ffc2b2f :  0.025973 s, 0.000303 s, -0.025670 s, × 0.011666
  mozilla-central x_revs_x00_added_x_copies             98cbc58cc6bc 446a150332c3 :  0.085098 s, 0.001663 s, -0.083435 s, × 0.019542
  mozilla-central x_revs_x000_added_x000_copies         3c684b4b8f68 0a5e72d1b479 :  0.196623 s, 0.007008 s, -0.189615 s, × 0.035642
  mozilla-central x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 :  2.182911 s, 0.127385 s, -2.055526 s, × 0.058356
  mozilla-central x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e :  0.088865 s, 0.008740 s, -0.080125 s, × 0.098351
  mozilla-central x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed :  0.731211 s, 0.005783 s, -0.725428 s, × 0.007909
  mozilla-central x000_revs_x000_added_x000_copies      7c97034feb78 4407bd0c6330 :  1.142414 s, 0.102184 s, -1.040230 s, × 0.089446
  mozilla-central x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad :  6.667504 s, 0.046220 s, -6.621284 s, × 0.006932
  mozilla-central x0000_revs_xx000_added_x000_copies    f78c615a656c 96a38b690156 :  3.267274 s, 0.315271 s, -2.952003 s, × 0.096494
  mozilla-central x00000_revs_x0000_added_x0000_copies  6832ae71433c 4c222a1d9a00 : 16.038104 s, 3.478747 s, -12.559357 s, × 0.216905
  mozilla-central x00000_revs_x00000_added_x000_copies  76caed42cf7c 1daa622bbe42 : 20.639928 s, 4.766435 s, -15.873493 s, × 0.230933
  mozilla-try     x_revs_x_added_0_copies               aaf6dde0deb8 9790f499805a : 0.080513 s, 0.001214 s, -0.079299 s, × 0.015078
  mozilla-try     x_revs_x000_added_0_copies            d8d0222927b4 5bb8ce8c7450 : 0.502965 s, 0.001221 s, -0.501744 s, × 0.002428
  mozilla-try     x_revs_x_added_x_copies               092fcca11bdb 936255a0384a : 0.021408 s, 0.000613 s, -0.020795 s, × 0.028634
  mozilla-try     x_revs_x00_added_x_copies             b53d2fadbdb5 017afae788ec : 0.228498 s, 0.001904 s, -0.226594 s, × 0.008333
  mozilla-try     x_revs_x000_added_x000_copies         20408ad61ce5 6f0ee96e21ad : 1.118490 s, 0.093000 s, -1.025490 s, × 0.083148
  mozilla-try     x_revs_x0000_added_x0000_copies       effb563bb7e5 c07a39dc4e80 : 2.188390 s, 0.132194 s, -2.056196 s, × 0.060407
  mozilla-try     x000_revs_xx00_added_0_copies         6100d773079a 04a55431795e : 0.089755 s, 0.009069 s, -0.080686 s, × 0.101042
  mozilla-try     x000_revs_x000_added_x_copies         9f17a6fc04f9 2d37b966abed : 0.750223 s, 0.006169 s, -0.744054 s, × 0.008223
  mozilla-try     x000_revs_x000_added_x000_copies      1346fd0130e4 4c65cbdabc1f : 1.189708 s, 0.115540 s, -1.074168 s, × 0.097116
  mozilla-try     x0000_revs_x_added_0_copies           63519bfd42ee a36a2a865d92 : 0.088715 s, 0.435381 s, +0.346666 s, × 4.907637
  mozilla-try     x0000_revs_x_added_x_copies           9fe69ff0762d bcabf2a78927 : 0.080765 s, 0.415461 s, +0.334696 s, × 5.144072
  mozilla-try     x0000_revs_xx000_added_x_copies       156f6e2674f2 4d0f2c178e66 : 7.487310 s, 0.155946 s, -7.331364 s, × 0.020828
  mozilla-try     x0000_revs_xx000_added_0_copies       9eec5917337d 67118cc6dcad : 6.676682 s, 0.048521 s, -6.628161 s, × 0.007267
  mozilla-try     x0000_revs_xx000_added_x000_copies    89294cd501d9 7ccb2fc7ccb5 : 7.598509 s, 9.843481 s, +2.244972 s, × 1.295449
  mozilla-try     x0000_revs_x0000_added_x0000_copies   e928c65095ed e951f4ad123a : 9.871850 s, 1.465128 s, -8.406722 s, × 0.148415
  mozilla-try     x00000_revs_x_added_0_copies          6a320851d377 1ebb79acd503 : 0.092232 s, killed
  mozilla-try     x00000_revs_x00000_added_0_copies     dc8a3ca7010e d16fde900c9c : 26.471560 s, 1.374283 s, -25.097277 s, × 0.051915
  mozilla-try     x00000_revs_x_added_x_copies          5173c4b6f97c 95d83ee7242d : 0.093892 s, killed
  mozilla-try     x00000_revs_x000_added_x_copies       9126823d0e9c ca82787bb23c : 0.227503 s, killed
  mozilla-try     x00000_revs_x0000_added_x0000_copies  8d3fafa80d4b eb884023b810 : 19.064699 s, 5.255158 s, -13.809541 s, × 0.275649
  mozilla-try     x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 21.145391 s, killed
  mozilla-try     x00000_revs_x00000_added_x000_copies  9b2a99adc05e 8e29777b48e6 : 25.304164 s, killed

REPOSITORY
  rHG Mercurial

BRANCH
  default

REVISION DETAIL
  https://phab.mercurial-scm.org/D9302

AFFECTED FILES
  rust/hg-core/src/copy_tracing.rs

CHANGE DETAILS




To: marmoute, #hg-reviewers
Cc: mercurial-patches, mercurial-devel

Patch

diff --git a/rust/hg-core/src/copy_tracing.rs b/rust/hg-core/src/copy_tracing.rs
--- a/rust/hg-core/src/copy_tracing.rs
+++ b/rust/hg-core/src/copy_tracing.rs
@@ -1,6 +1,7 @@ 
 use crate::utils::hg_path::HgPathBuf;
 use crate::Revision;
 
+use im_rc::ordmap::DiffItem;
 use im_rc::ordmap::OrdMap;
 
 use std::collections::HashMap;
@@ -8,7 +9,7 @@ 
 
 pub type PathCopies = HashMap<HgPathBuf, HgPathBuf>;
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, PartialEq)]
 struct TimeStampedPathCopy {
     /// revision at which the copy information was added
     rev: Revision,
@@ -202,70 +203,116 @@ 
     changes: &ChangedFiles,
     is_ancestor: &impl Fn(Revision, Revision) -> bool,
 ) -> TimeStampedPathCopies {
-    let mut result = minor.clone();
-    for (dest, src_major) in major.into_iter() {
-        let overwrite;
-        if let Some(src_minor) = minor.get(&dest) {
-            {
+    if minor.is_empty() {
+        return major;
+    } else if major.is_empty() {
+        return minor;
+    }
+    let mut override_minor = Vec::new();
+    let mut override_major = Vec::new();
+
+    let mut to_major = |k: &HgPathBuf, v: &TimeStampedPathCopy| {
+        override_major.push((k.clone(), v.clone()))
+    };
+    let mut to_minor = |k: &HgPathBuf, v: &TimeStampedPathCopy| {
+        override_minor.push((k.clone(), v.clone()))
+    };
+
+    // The diff function leverage detection of the identical subpart if minor
+    // and major has some common ancestors. This make it very fast is most
+    // case.
+    //
+    // In case where the two map are vastly different in size, the current
+    // approach is still slowish because the iteration will iterate over
+    // all the "exclusive" content of the larger on. This situation can be
+    // frequent when the subgraph of revision we are processing has a lot
+    // of roots. Each roots adding they own fully new map to the mix (and
+    // likely a small map, if the path from the root to the "main path" is
+    // small.
+    //
+    // We could do better by detecting such situation and processing them
+    // differently.
+    for d in minor.diff(&major) {
+        match d {
+            DiffItem::Add(k, v) => to_minor(k, v),
+            DiffItem::Remove(k, v) => to_major(k, v),
+            DiffItem::Update { old, new } => {
+                let (dest, src_major) = new;
+                let (_, src_minor) = old;
+                let mut pick_minor = || (to_major(dest, src_minor));
+                let mut pick_major = || (to_minor(dest, src_major));
                 if src_major.path == src_minor.path {
-                    // we have the same value, no need to battle;
+                    // we have the same value, but from other source;
                     if src_major.rev == src_minor.rev {
                         // If the two entry are identical, no need to do
-                        // anything
-                        overwrite = false;
+                        // anything (but diff should not have yield them)
+                        unreachable!();
                     } else if is_ancestor(src_major.rev, src_minor.rev) {
-                        overwrite = false;
+                        pick_minor();
                     } else {
-                        overwrite = true;
+                        pick_major();
                     }
                 } else if src_major.rev == src_minor.rev {
                     // We cannot get copy information for both p1 and p2 in the
                     // same rev. So this is the same value.
-                    overwrite = false;
+                    unreachable!();
                 } else if src_major.path.is_none()
-                    && changes.salvaged.contains(&dest)
+                    && changes.salvaged.contains(dest)
                 {
                     // If the file is "deleted" in the major side but was
                     // salvaged by the merge, we keep the minor side alive
-                    overwrite = false;
+                    pick_minor();
                 } else if src_minor.path.is_none()
-                    && changes.salvaged.contains(&dest)
+                    && changes.salvaged.contains(dest)
                 {
                     // If the file is "deleted" in the minor side but was
                     // salvaged by the merge, unconditionnaly preserve the
                     // major side.
-                    overwrite = true;
-                } else if changes.merged.contains(&dest) {
+                    pick_major();
+                } else if changes.merged.contains(dest) {
                     // If the file was actively merged, copy information from
                     // each side might conflict.  The major side will win such
                     // conflict.
-                    overwrite = true;
+                    pick_major();
                 } else if is_ancestor(src_major.rev, src_minor.rev) {
                     // If the minor side is strictly newer than the major side,
                     // it should be kept.
-                    overwrite = false;
+                    pick_minor();
                 } else if src_major.path.is_some() {
                     // without any special case, the "major" value win other
                     // the "minor" one.
-                    overwrite = true;
+                    pick_major();
                 } else if is_ancestor(src_minor.rev, src_major.rev) {
                     // the "major" rev is a direct ancestors of "minor", any
                     // different value should overwrite
-                    overwrite = true;
+                    pick_major();
                 } else {
                     // major version is None (so the file was deleted on that
                     // branch) and that branch is independant (neither minor
                     // nor major is an ancestors of the other one.) We preserve
                     // the new information about the new file.
-                    overwrite = false;
+                    pick_minor();
                 }
             }
+        };
+    }
+
+    let updates;
+    let mut result;
+    if override_major.is_empty() {
+        result = major
+    } else if override_minor.is_empty() {
+        result = minor
+    } else {
+        if override_minor.len() < override_major.len() {
+            updates = override_minor;
+            result = minor;
         } else {
-            // minor had no value
-            overwrite = true;
+            updates = override_major;
+            result = major;
         }
-        if overwrite {
-            result.insert(dest, src_major);
+        for (k, v) in updates {
+            result.insert(k, v);
         }
     }
     result