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comparison tests/test-sparse-revlog.t @ 39523:b66ea3fc3a86

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sparse-revlog: set max delta chain length to on thousand The new snapshot system used in the sparse-revlog case gave us some small size benefit so far. However its most important property is to gracefully handle harder limit on delta chainlength. Long delta chain has a very detrimental impact on read (and write) performance in revlog. Being able to shorter them provide a great boost. However, shorting delta used to result significantly lower compression ratio. The intermediate snapshots effectively suppress most of this effect (even all in some case). # Effect on the test repository The repository we use for test is not "realistic" but can still show this in action using an unreasonably low chain limit. Limiting the chain length show a sizeable increase but stay under control: +6% for limit=15; +15% for limit=10. Without the snapshot system the increase is significantly bigger: +45% for limit=15; +80% for limit=10. Even slightly larger than without delta chain limit, the resulting size is still smaller than before we started doing snapshots. Here is a table for comparison. *Since the repository is not branchy, the initial sparse-revlog version does not bring much benefit compare to the non-sparse one): chain length limit | none | limit=15 | limit=10 | without sparse-revlog | 62 818 987 | 112 664 615 | 131 222 574 | without snapshot | 74 365 490 | 108 211 410 | 133 857 764 | with snapshot | 59 230 936 | 63 002 924 | 68 415 329 | # Effect On Real Life Repositories The series provides significant benefits on all kind of repositories. Using `hg debugupgraderepo -o redeltaparent --run`, we recomputed delta chain for various repositories with different settings: - delta chain length: unlimited or 1000 limit - sparse-revlog: enabled or disabled - this series: applied or not applied We can observe multiple types of effect: - On very branchy repositories: * The delta chain limit as low impact on the repo size. * Intermediate snapshot greatly reduces manifest size: - pypy: -80% - netbeans: -95% * The delta chain limit is effective, without a size impact: - netbeans average: 613 -> 282 - private #1 average: 1 068 -> 307 - On more linear repository: * Intermediate snapshot limit the impact of delta chain limit: - mozilla: without the series: +360% with the series: +25% * The delta chain limit provides large improvement: - mozilla's average chain length: unlimited: 15 338 limited: 469 * Despite the chain length limit, the manifest size is reduced: - mercurial: -25% - mozilla: -30% It is clear that the use of chains of intermediate snapshots provide large benefits both in storage size and delta chains quality. We should now switch our effort toward making sure the write performance are acceptable. Then, `sparse-revlog` will be a suitable format for all new repository. # Raw Statistic * no-sparse: general delta repository not using sparse-revlog * no-snapshot: sparse-revlog repository not using this series * snapshot: sparse-revlog repository using this series mercurial Manifest Size: limit | none | 1000 ------------|-------------|------------ no-sparse | 8 021 373 | 8 199 366 no-snapshot | 8 103 561 | 8 259 719 snapshot | 6 137 116 | 6 126 433 Manifest Chain length data limit || none || 1000 || value || average | max || average | max || ------------||---------|---------||---------|---------|| no-sparse || 307 | 1456 || 279 | 1000 || no-snapshot || 312 | 1456 || 283 | 1000 || snapshot || 248 | 1208 || 241 | 1000 || Full Store Size limit | none | 1000 ------------|-------------|------------ no-sparse | 51 013 198 | 51 201 574 no-snapshot | 50 930 795 | 51 141 006 snapshot | 48 072 037 | 48 093 572 pypy Manifest Size: limit | none | 1000 ------------|-------------|------------ no-sparse | 193 987 784 | 193 987 784 no-snapshot | 163 171 745 | 163 312 229 snapshot | 34 605 900 | 34 600 750 Manifest Chain length data limit || none || 1000 || value || average | max || average | max || ------------||---------|---------||---------|---------|| no-sparse || 101 | 692 || 101 | 692 || no-snapshot || 151 | 1307 || 148 | 1000 || snapshot || 128 | 1309 || 125 | 1000 || Full Store Size limit | none | 1000 ------------|-------------|------------ no-sparse | 495 931 473 | 495 931 473 no-snapshot | 465 441 017 | 465 581 501 snapshot | 355 467 301 | 355 472 451 Mozilla Manifest Size: limit | none | 1000 ------------|----------------|--------------- no-sparse | 416 757 148 | 1 869 009 668 no-snapshot | 401 592 370 | 1 843 493 795 snapshot | 224 359 521 | 284 615 500 Manifest Chain length data limit || none || 1000 || value || average | max || average | max || ------------||---------|---------||---------|---------|| no-sparse || 15 333 | 58 980 || 468 | 1 000 || no-snapshot || 15 336 | 58 980 || 469 | 1 000 || snapshot || 15 338 | 58 983 || 469 | 1 000 || Full Store Size limit | none | 1000 ------------|----------------|--------------- no-sparse | 2 712 477 887 | 4 164 995 451 no-snapshot | 2 698 887 835 | 4 141 054 304 snapshot | 2 518 130 385 | 2 578 587 596 Netbeans Manifest Size: limit | none | 1000 ------------|----------------|--------------- no-sparse | 4 766 794 101 | 4 870 642 687 no-snapshot | 4 334 806 082 | 4 428 681 309 snapshot | 232 659 666 | 240 330 665 Manifest Chain length data limit || none || 1000 || value || average | max || average | max || ------------||---------|---------||---------|---------|| no-sparse || 597 | 6802 || 254 | 1 000 || no-snapshot || 648 | 6 802 || 305 | 1 000 || snapshot || 613 | 6 804 || 282 | 1 000 || Full Store Size limit | none | 1000 ------------|----------------|--------------- no-sparse | 5 807 347 998 | 5 911 196 584 no-snapshot | 5 375 398 602 | 5 469 273 829 snapshot | 1 282 519 928 | 1 290 190 927 Private repo #1 Manifest Size: limit | none | 1000 ------------|-----------------|--------------- no-sparse | 41 389 010 840 | 41 398 162 091 no-snapshot | 9 737 319 435 | 10 223 773 150 snapshot | 744 215 807 | 747 961 822 Manifest Chain length data limit || none || 1000 || value || average | max || average | max || ------------||---------|---------||---------|---------|| no-sparse || 245 | 8 885 || 81 | 1 000 || no-snapshot || 1 225 | 8 885 || 336 | 1 000 || snapshot || 1 068 | 7 909 || 307 | 1 000 || Full Store Size limit | none | 1000 ------------|----------------|--------------- no-sparse | 49 646 065 126 | 49 655 216 377 no-snapshot | 17 924 862 856 | 18 411 316 571 snapshot | 9 009 024 710 | 9 012 770 725 Private repo #2 We currently have less data available for that repository. * Before is a sparse-revlog repository without this series * After is a sparse-revlog repository with this series + 1000 chain limit Manifest Size: Before: 1 531 485 040 bytes After: 1 091 422 451 bytes Manifest Chain: Before: 2 218 avg; 6 575 Max After: 442 avg; 1 000 Max Full Store Size Before: 15 203 955 615 after: 8 207 180 693
author Boris Feld <boris.feld@octobus.net>
date Fri, 07 Sep 2018 11:18:45 -0400
parents c6b8eab5db19
children 2e92624c3613
comparison
equal deleted inserted replaced
39522:c6b8eab5db19 39523:b66ea3fc3a86
23 > fi 23 > fi
24 24
25 $ cat >> $HGRCPATH << EOF 25 $ cat >> $HGRCPATH << EOF
26 > [format] 26 > [format]
27 > sparse-revlog = yes 27 > sparse-revlog = yes
28 > maxchainlen = 15
28 > [storage] 29 > [storage]
29 > revlog.optimize-delta-parent-choice = yes 30 > revlog.optimize-delta-parent-choice = yes
30 > EOF 31 > EOF
31 $ hg init sparse-repo 32 $ hg init sparse-repo
32 $ cd sparse-repo 33 $ cd sparse-repo
75 SPARSE-REVLOG-TEST-FILE | 1068 +++++++++++++++++++++++----------------------- 76 SPARSE-REVLOG-TEST-FILE | 1068 +++++++++++++++++++++++-----------------------
76 1 files changed, 534 insertions(+), 534 deletions(-) 77 1 files changed, 534 insertions(+), 534 deletions(-)
77 78
78 79
79 $ f -s .hg/store/data/*.d 80 $ f -s .hg/store/data/*.d
80 .hg/store/data/_s_p_a_r_s_e-_r_e_v_l_o_g-_t_e_s_t-_f_i_l_e.d: size=59230936 81 .hg/store/data/_s_p_a_r_s_e-_r_e_v_l_o_g-_t_e_s_t-_f_i_l_e.d: size=63002924
81 $ hg debugrevlog * 82 $ hg debugrevlog *
82 format : 1 83 format : 1
83 flags : generaldelta 84 flags : generaldelta
84 85
85 revisions : 5001 86 revisions : 5001
87 normal : 4376 (87.50%) 88 normal : 4376 (87.50%)
88 revisions : 5001 89 revisions : 5001
89 empty : 0 ( 0.00%) 90 empty : 0 ( 0.00%)
90 text : 0 (100.00%) 91 text : 0 (100.00%)
91 delta : 0 (100.00%) 92 delta : 0 (100.00%)
92 snapshot : 176 ( 3.52%) 93 snapshot : 374 ( 7.48%)
93 lvl-0 : 3 ( 0.06%) 94 lvl-0 : 4 ( 0.08%)
94 lvl-1 : 17 ( 0.34%) 95 lvl-1 : 23 ( 0.46%)
95 lvl-2 : 45 ( 0.90%) 96 lvl-2 : 63 ( 1.26%)
96 lvl-3 : 56 ( 1.12%) 97 lvl-3 : 118 ( 2.36%)
97 lvl-4 : 55 ( 1.10%) 98 lvl-4 : 166 ( 3.32%)
98 deltas : 4825 (96.48%) 99 deltas : 4627 (92.52%)
99 revision size : 59230936 100 revision size : 63002924
100 snapshot : 5770371 ( 9.74%) 101 snapshot : 9888099 (15.69%)
101 lvl-0 : 602962 ( 1.02%) 102 lvl-0 : 804262 ( 1.28%)
102 lvl-1 : 1534153 ( 2.59%) 103 lvl-1 : 1561380 ( 2.48%)
103 lvl-2 : 1604445 ( 2.71%) 104 lvl-2 : 2096696 ( 3.33%)
104 lvl-3 : 1218174 ( 2.06%) 105 lvl-3 : 2749539 ( 4.36%)
105 lvl-4 : 810637 ( 1.37%) 106 lvl-4 : 2676222 ( 4.25%)
106 deltas : 53460565 (90.26%) 107 deltas : 53114825 (84.31%)
107 108
108 chunks : 5001 109 chunks : 5001
109 0x78 (x) : 5001 (100.00%) 110 0x78 (x) : 5001 (100.00%)
110 chunks size : 59230936 111 chunks size : 63002924
111 0x78 (x) : 59230936 (100.00%) 112 0x78 (x) : 63002924 (100.00%)
112 113
113 avg chain length : 17 114 avg chain length : 9
114 max chain length : 45 115 max chain length : 15
115 max chain reach : 25326012 116 max chain reach : 28907121
116 compression ratio : 29 117 compression ratio : 27
117 118
118 uncompressed data size (min/max/avg) : 346468 / 346472 / 346471 119 uncompressed data size (min/max/avg) : 346468 / 346472 / 346471
119 full revision size (min/max/avg) : 200897 / 201050 / 200987 120 full revision size (min/max/avg) : 201008 / 201141 / 201065
120 inter-snapshot size (min/max/avg) : 11598 / 171990 / 29869 121 inter-snapshot size (min/max/avg) : 11601 / 157413 / 24550
121 level-1 (min/max/avg) : 14037 / 171990 / 90244 122 level-1 (min/max/avg) : 13061 / 157413 / 67886
122 level-2 (min/max/avg) : 11632 / 84456 / 35654 123 level-2 (min/max/avg) : 11674 / 85631 / 33280
123 level-3 (min/max/avg) : 11598 / 41486 / 21753 124 level-3 (min/max/avg) : 11602 / 42957 / 23301
124 level-4 (min/max/avg) : 11618 / 19913 / 14738 125 level-4 (min/max/avg) : 11601 / 21475 / 16121
125 delta size (min/max/avg) : 10649 / 105209 / 11079 126 delta size (min/max/avg) : 10649 / 105465 / 11479
126 127
127 deltas against prev : 4156 (86.13%) 128 deltas against prev : 3966 (85.71%)
128 where prev = p1 : 4120 (99.13%) 129 where prev = p1 : 3922 (98.89%)
129 where prev = p2 : 0 ( 0.00%) 130 where prev = p2 : 0 ( 0.00%)
130 other : 36 ( 0.87%) 131 other : 44 ( 1.11%)
131 deltas against p1 : 646 (13.39%) 132 deltas against p1 : 611 (13.21%)
132 deltas against p2 : 23 ( 0.48%) 133 deltas against p2 : 50 ( 1.08%)
133 deltas against other : 0 ( 0.00%) 134 deltas against other : 0 ( 0.00%)