copies-rust: add smarter approach for merging small mapping with large mapping The current approach (finding the smaller updated set) works great when the mapping have similar size, but do a lot of unnecessary work when one side is tinier than the other one. So we do better in theses cases. See inline documentation for details. It give a sizeable boost to many of out slower cases: Repo Case Source-Rev Dest-Rev # of revisions old time new time Difference Factor time per rev --------------------------------------------------------------------------------------------------------------------------------------------------------------- mozilla-try x00000_revs_x_added_0_copies 6a320851d377 1ebb79acd503 : 363753 revs, 18.123103 s, 5.693818 s, -12.429285 s, ? 0.3142, 15 ?s/rev mozilla-try x00000_revs_x_added_x_copies 5173c4b6f97c 95d83ee7242d : 362229 revs, 17.907312 s, 5.677655 s, -12.229657 s, ? 0.3171, 15 ?s/rev mozilla-try x00000_revs_x000_added_x_copies 9126823d0e9c ca82787bb23c : 359344 revs, 17.684797 s, 5.563370 s, -12.121427 s, ? 0.3146, 15 ?s/rev mozilla-try x00000_revs_x0000_added_x0000_copies 8d3fafa80d4b eb884023b810 : 192665 revs, 2.881471 s, 2.864099 s, -0.017372 s, ? 0.9940, 14 ?s/rev mozilla-try x00000_revs_x00000_added_x000_copies 9b2a99adc05e 8e29777b48e6 : 382065 revs, 63.148971 s, 59.498652 s, -3.650319 s, ? 0.9422, 155 ?s/rev mozilla-try x00000_revs_x00000_added_x000_copies 9b2a99adc05e 8e29777b48e6 : 382065 revs, 63.148971 s, 59.498652 s, -3.650319 s, ? 0.9422, 155 ?s/rev ideally, the im-rs object would have a `merge` method, but it does not (yet) Full timing comparison below (they are one pathological case than become even worse, for unclear reason). Repo Case Source-Rev Dest-Rev # of revisions old time new time Difference Factor time per rev --------------------------------------------------------------------------------------------------------------------------------------------------------------- mercurial x_revs_x_added_0_copies ad6b123de1c7 39cfcef4f463 : 1 revs, 0.000043 s, 0.000042 s, -0.000001 s, ? 0.9767, 42 ?s/rev mercurial x_revs_x_added_x_copies 2b1c78674230 0c1d10351869 : 6 revs, 0.000105 s, 0.000104 s, -0.000001 s, ? 0.9905, 17 ?s/rev mercurial x000_revs_x000_added_x_copies 81f8ff2a9bf2 dd3267698d84 : 1032 revs, 0.004895 s, 0.004913 s, +0.000018 s, ? 1.0037, 4 ?s/rev pypy x_revs_x_added_0_copies aed021ee8ae8 099ed31b181b : 9 revs, 0.000194 s, 0.000191 s, -0.000003 s, ? 0.9845, 21 ?s/rev pypy x_revs_x000_added_0_copies 4aa4e1f8e19a 359343b9ac0e : 1 revs, 0.000050 s, 0.000050 s, +0.000000 s, ? 1.0000, 50 ?s/rev pypy x_revs_x_added_x_copies ac52eb7bbbb0 72e022663155 : 7 revs, 0.000115 s, 0.000112 s, -0.000003 s, ? 0.9739, 16 ?s/rev pypy x_revs_x00_added_x_copies c3b14617fbd7 ace7255d9a26 : 1 revs, 0.000289 s, 0.000288 s, -0.000001 s, ? 0.9965, 288 ?s/rev pypy x_revs_x000_added_x000_copies df6f7a526b60 a83dc6a2d56f : 6 revs, 0.010513 s, 0.010411 s, -0.000102 s, ? 0.9903, 1735 ?s/rev pypy x000_revs_xx00_added_0_copies 89a76aede314 2f22446ff07e : 4785 revs, 0.051474 s, 0.052852 s, +0.001378 s, ? 1.0268, 11 ?s/rev pypy x000_revs_x000_added_x_copies 8a3b5bfd266e 2c68e87c3efe : 6780 revs, 0.088086 s, 0.092828 s, +0.004742 s, ? 1.0538, 13 ?s/rev pypy x000_revs_x000_added_x000_copies 89a76aede314 7b3dda341c84 : 5441 revs, 0.062176 s, 0.063269 s, +0.001093 s, ? 1.0176, 11 ?s/rev pypy x0000_revs_x_added_0_copies d1defd0dc478 c9cb1334cc78 : 43645 revs, 0.720950 s, 0.711975 s, -0.008975 s, ? 0.9876, 16 ?s/rev pypy x0000_revs_xx000_added_0_copies bf2c629d0071 4ffed77c095c : 2 revs, 0.012897 s, 0.012771 s, -0.000126 s, ? 0.9902, 6385 ?s/rev pypy x0000_revs_xx000_added_x000_copies 08ea3258278e d9fa043f30c0 : 11316 revs, 0.121524 s, 0.124505 s, +0.002981 s, ? 1.0245, 11 ?s/rev netbeans x_revs_x_added_0_copies fb0955ffcbcd a01e9239f9e7 : 2 revs, 0.000082 s, 0.000082 s, +0.000000 s, ? 1.0000, 41 ?s/rev netbeans x_revs_x000_added_0_copies 6f360122949f 20eb231cc7d0 : 2 revs, 0.000109 s, 0.000111 s, +0.000002 s, ? 1.0183, 55 ?s/rev netbeans x_revs_x_added_x_copies 1ada3faf6fb6 5a39d12eecf4 : 3 revs, 0.000175 s, 0.000171 s, -0.000004 s, ? 0.9771, 57 ?s/rev netbeans x_revs_x00_added_x_copies 35be93ba1e2c 9eec5e90c05f : 9 revs, 0.000719 s, 0.000708 s, -0.000011 s, ? 0.9847, 78 ?s/rev netbeans x000_revs_xx00_added_0_copies eac3045b4fdd 51d4ae7f1290 : 1421 revs, 0.010426 s, 0.010608 s, +0.000182 s, ? 1.0175, 7 ?s/rev netbeans x000_revs_x000_added_x_copies e2063d266acd 6081d72689dc : 1533 revs, 0.015712 s, 0.015635 s, -0.000077 s, ? 0.9951, 10 ?s/rev netbeans x000_revs_x000_added_x000_copies ff453e9fee32 411350406ec2 : 5750 revs, 0.077353 s, 0.072072 s, -0.005281 s, ? 0.9317, 12 ?s/rev netbeans x0000_revs_xx000_added_x000_copies 588c2d1ced70 1aad62e59ddd : 66949 revs, 0.673930 s, 0.682732 s, +0.008802 s, ? 1.0131, 10 ?s/rev mozilla-central x_revs_x_added_0_copies 3697f962bb7b 7015fcdd43a2 : 2 revs, 0.000089 s, 0.000090 s, +0.000001 s, ? 1.0112, 45 ?s/rev mozilla-central x_revs_x000_added_0_copies dd390860c6c9 40d0c5bed75d : 8 revs, 0.000212 s, 0.000210 s, -0.000002 s, ? 0.9906, 26 ?s/rev mozilla-central x_revs_x_added_x_copies 8d198483ae3b 14207ffc2b2f : 9 revs, 0.000183 s, 0.000182 s, -0.000001 s, ? 0.9945, 20 ?s/rev mozilla-central x_revs_x00_added_x_copies 98cbc58cc6bc 446a150332c3 : 7 revs, 0.000595 s, 0.000594 s, -0.000001 s, ? 0.9983, 84 ?s/rev mozilla-central x_revs_x000_added_x000_copies 3c684b4b8f68 0a5e72d1b479 : 3 revs, 0.003117 s, 0.003102 s, -0.000015 s, ? 0.9952, 1034 ?s/rev mozilla-central x_revs_x0000_added_x0000_copies effb563bb7e5 c07a39dc4e80 : 6 revs, 0.060197 s, 0.060234 s, +0.000037 s, ? 1.0006, 10039 ?s/rev mozilla-central x000_revs_xx00_added_0_copies 6100d773079a 04a55431795e : 1593 revs, 0.006379 s, 0.006300 s, -0.000079 s, ? 0.9876, 3 ?s/rev mozilla-central x000_revs_x000_added_x_copies 9f17a6fc04f9 2d37b966abed : 41 revs, 0.005008 s, 0.004817 s, -0.000191 s, ? 0.9619, 117 ?s/rev mozilla-central x000_revs_x000_added_x000_copies 7c97034feb78 4407bd0c6330 : 7839 revs, 0.065123 s, 0.065451 s, +0.000328 s, ? 1.0050, 8 ?s/rev mozilla-central x0000_revs_xx000_added_0_copies 9eec5917337d 67118cc6dcad : 615 revs, 0.026404 s, 0.026282 s, -0.000122 s, ? 0.9954, 42 ?s/rev mozilla-central x0000_revs_xx000_added_x000_copies f78c615a656c 96a38b690156 : 30263 revs, 0.203456 s, 0.206873 s, +0.003417 s, ? 1.0168, 6 ?s/rev mozilla-central x00000_revs_x0000_added_x0000_copies 6832ae71433c 4c222a1d9a00 : 153721 revs, 1.929809 s, 1.935918 s, +0.006109 s, ? 1.0032, 12 ?s/rev mozilla-central x00000_revs_x00000_added_x000_copies 76caed42cf7c 1daa622bbe42 : 204976 revs, 2.825064 s, 2.827320 s, +0.002256 s, ? 1.0008, 13 ?s/rev mozilla-try x_revs_x_added_0_copies aaf6dde0deb8 9790f499805a : 2 revs, 0.000857 s, 0.000842 s, -0.000015 s, ? 0.9825, 421 ?s/rev mozilla-try x_revs_x000_added_0_copies d8d0222927b4 5bb8ce8c7450 : 2 revs, 0.000870 s, 0.000870 s, +0.000000 s, ? 1.0000, 435 ?s/rev mozilla-try x_revs_x_added_x_copies 092fcca11bdb 936255a0384a : 4 revs, 0.000161 s, 0.000165 s, +0.000004 s, ? 1.0248, 41 ?s/rev mozilla-try x_revs_x00_added_x_copies b53d2fadbdb5 017afae788ec : 2 revs, 0.001147 s, 0.001145 s, -0.000002 s, ? 0.9983, 572 ?s/rev mozilla-try x_revs_x000_added_x000_copies 20408ad61ce5 6f0ee96e21ad : 1 revs, 0.026640 s, 0.026500 s, -0.000140 s, ? 0.9947, 26500 ?s/rev mozilla-try x_revs_x0000_added_x0000_copies effb563bb7e5 c07a39dc4e80 : 6 revs, 0.059849 s, 0.059407 s, -0.000442 s, ? 0.9926, 9901 ?s/rev mozilla-try x000_revs_xx00_added_0_copies 6100d773079a 04a55431795e : 1593 revs, 0.006326 s, 0.006325 s, -0.000001 s, ? 0.9998, 3 ?s/rev mozilla-try x000_revs_x000_added_x_copies 9f17a6fc04f9 2d37b966abed : 41 revs, 0.005188 s, 0.005171 s, -0.000017 s, ? 0.9967, 126 ?s/rev mozilla-try x000_revs_x000_added_x000_copies 1346fd0130e4 4c65cbdabc1f : 6657 revs, 0.067633 s, 0.066837 s, -0.000796 s, ? 0.9882, 10 ?s/rev mozilla-try x0000_revs_x_added_0_copies 63519bfd42ee a36a2a865d92 : 40314 revs, 0.306969 s, 0.314252 s, +0.007283 s, ? 1.0237, 7 ?s/rev mozilla-try x0000_revs_x_added_x_copies 9fe69ff0762d bcabf2a78927 : 38690 revs, 0.293370 s, 0.304160 s, +0.010790 s, ? 1.0368, 7 ?s/rev mozilla-try x0000_revs_xx000_added_x_copies 156f6e2674f2 4d0f2c178e66 : 8598 revs, 0.087159 s, 0.089223 s, +0.002064 s, ? 1.0237, 10 ?s/rev mozilla-try x0000_revs_xx000_added_0_copies 9eec5917337d 67118cc6dcad : 615 revs, 0.027251 s, 0.026711 s, -0.000540 s, ? 0.9802, 43 ?s/rev mozilla-try x0000_revs_xx000_added_x000_copies 89294cd501d9 7ccb2fc7ccb5 : 97052 revs, 3.010011 s, 3.243010 s, +0.232999 s, ? 1.0774, 33 ?s/rev mozilla-try x0000_revs_x0000_added_x0000_copies e928c65095ed e951f4ad123a : 52031 revs, 0.753434 s, 0.756500 s, +0.003066 s, ? 1.0041, 14 ?s/rev mozilla-try x00000_revs_x_added_0_copies 6a320851d377 1ebb79acd503 : 363753 revs, 18.123103 s, 5.693818 s, -12.429285 s, ? 0.3142, 15 ?s/rev mozilla-try x00000_revs_x00000_added_0_copies dc8a3ca7010e d16fde900c9c : 34414 revs, 0.583206 s, 0.590904 s, +0.007698 s, ? 1.0132, 17 ?s/rev mozilla-try x00000_revs_x_added_x_copies 5173c4b6f97c 95d83ee7242d : 362229 revs, 17.907312 s, 5.677655 s, -12.229657 s, ? 0.3171, 15 ?s/rev mozilla-try x00000_revs_x000_added_x_copies 9126823d0e9c ca82787bb23c : 359344 revs, 17.684797 s, 5.563370 s, -12.121427 s, ? 0.3146, 15 ?s/rev mozilla-try x00000_revs_x0000_added_x0000_copies 8d3fafa80d4b eb884023b810 : 192665 revs, 2.881471 s, 2.864099 s, -0.017372 s, ? 0.9940, 14 ?s/rev mozilla-try x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 228985 revs, 101.062002 s, 113.297287 s, +12.235285 s, ? 1.1211, 494 ?s/rev mozilla-try x00000_revs_x00000_added_x000_copies 9b2a99adc05e 8e29777b48e6 : 382065 revs, 63.148971 s, 59.498652 s, -3.650319 s, ? 0.9422, 155 ?s/rev Differential Revision: https://phab.mercurial-scm.org/D9491