wireprotov2: unify file revision collection and linknode derivation The old mechanism for choosing which file revisions to send in the haveparents=True case was buggy in multiple ways - the most severe of which being that file revisions were excluded when they shouldn't have been. This commit unifies the logic for deriving the filenodes that will be sent by the "filesdata" command. We now consistently read files data from manifests. The "haveparents" argument now controls whether we iterate ctx.files() or use the full manifest to derive relevant files. The logic here is still woefully lacking to fully support shallow clones. It will require an API break to fully address. This commit should at least make the server APIs emit proper data, which is strictly better than before. Differential Revision: https://phab.mercurial-scm.org/D5406

wireprotov2: send linknodes to emitfilerevisions() Previously, linknodes were calculated within emitfilerevisions() by using filectx.introrev(), which would always use the linkrev/linknode as recorded by storage. This is wrong for cases where the receiver doesn't have the changeset the linknode refers to. This commit changes the logic for linknode emission so the mapping of filenode to linknode is computed by the caller and passed into emitfilerevisions(). As part of the change, linknodes for "filesdata" in the haveparents=False case are now correct: the existing code performed a manifest walk and it was trivial to plug in the correct linknode. However, behavior for the haveparents=True case is still wrong because it relies on filtering linkrevs against the outgoing set in order to determine what to send. This will be fixed in a subsequent commit. The change test test-wireproto-exchangev2-shallow.t is a bit wonky. The test repo has 6 revisions. The changed test is performing a shallow clone with depth=1. So, only file data for revision 5 is present locally. So, the new behavior of associating the linknode with revision 5 for every file revision seems correct. Of course, when backfilling old revisions, we'll want to update the linknode. But this problem requires wire protocol support and we'll cross that bridge later. Differential Revision: https://phab.mercurial-scm.org/D5405

tests: add tests for server-side linknode adjustment with wireprotov2 The current implementation of linknode serving in wireprotov2 simply serves up the linkrev/linknode as stored: it doesn't attempt to adjust the linknode to what the receiver is aware of. This can result in the client seeing a linknode referencing a changeset that is unknown to it. This commit adds test coverage of that scenario. The tests in test-wireproto-command-filesdata.t demonstrate two failures. First, the linknode refers to a changeset not in the available set. Second, the server doesn't send a file revision that it should have (because of linkrev filtering). The test in test-wireproto-exchange.t demonstrates that the lack of a file revision results in a corrupted repository on the client. Differential Revision: https://phab.mercurial-scm.org/D5404

tests: fix empty commit in test This was almost certainly a bug. Differential Revision: https://phab.mercurial-scm.org/D5403

tests: add sparserevlog requirement to test-sqlitestore.t Looks like this test was missed when enabling sparse revlogs by default. Differential Revision: https://phab.mercurial-scm.org/D5402

tests: remove all transitional configuration Now that sparse-revlog is enabled by default, we no longer needs it. Differential Revision: https://phab.mercurial-scm.org/D5346

sparse-revlog: enabled by default The feature provides large benefits. It now seems mature enough to be enabled by default. * It solves catastrophic issues regarding delta storage in revlog, * It allows for shorter delta chain in all repositories, improving performances. Running benchmark of a wide range of operation did not reveal problematic impact. Performance gains are observed where expected. The format is supported by Mercurial version 4.7. So it seems safe to enable it by default now. Here is a reminder of key numbers regarding this delta strategy effect on repository size and performance. Effect on Size: =============== For repositories with a lot of branches, sparse-revlog significantly improve size, fixing limitation associated with the span of a delta chain. In addition, sparse-revlog, deal well with limitations of the delta chain length. For large repositories, this allows for a stiff reduction of the delta chain without a problematic impact on the repository size. This delta chain length improvement helps all repositories, not just the ones with many branches. As a reminder, here are the default chain limits for each "format": * no-sparse: none * sparse: 1000 Mercurial --------- Manifest Size: limit | none | 1000 ------------|-------------|------------ no-sparse | 6 143 044 | 6 269 496 sparse | 5 798 796 | 5 827 025 Manifest Chain length data limit || none || 1000 value || average | max || average | max ------------||---------|---------||---------|--------- no-sparse || 429 | 1 397 || 397 | 1 000 sparse || 326 | 1 290 || 313 | 1 000 Full Store Size limit | none | 1000 ------------|-------------|------------ no-sparse | 46 944 775 | 47 166 129 sparse | 46 622 445 | 46 723 774 pypy ---- Manifest Size: limit | none | 1000 ------------|-------------|------------ no-sparse | 52 941 760 | 56 200 970 sparse | 26 348 229 | 27 384 133 Manifest Chain length data limit || none || 1000 value || average | max || average | max ------------||---------|---------||---------|--------- no-sparse || 769 | 3 889 || 390 | 1 000 sparse || 1 223 | 3 846 || 495 | 1 000 Full Store Size limit | none | 1000 ------------|-------------|------------ no-sparse | 336 050 203 | 339 309 413 sparse | 338 673 985 | 339 709 889 Mozilla ------- Manifest Size: limit | none | 1000 ------------|----------------|--------------- no-sparse | 215 096 339 | 1 708 853 525 sparse | 188 947 271 | 278 894 170 Manifest Chain length data limit || none || 1000 value || average | max || average | max ------------||---------|---------||---------|-------- no-sparse || 20 454 | 59 562 || 491 | 1 000 sparse || 23 509 | 69 891 || 489 | 1 000 Full Store Size limit | none | 1000 ------------|----------------|--------------- no-sparse | 2 377 578 715 | 3 876 258 798 sparse | 2 441 677 137 | 2 535 997 381 Netbeans -------- Manifest Size: limit | none | 1000 ------------|----------------|--------------- no-sparse | 130 088 982 | 741 590 565 sparse | 118 836 887 | 159 161 207 Manifest Chain length data limit || none || 1000 value || average | max || average | max ------------||---------|---------||---------|--------- no-sparse || 19 321 | 61 397 || 510 | 1 000 sparse || 21 240 | 61 583 || 503 | 1 000 Full Store Size limit | none | 1000 ------------|----------------|--------------- no-sparse | 1 160 013 008 | 1 771 514 591 sparse | 1 164 959 988 | 1 205 284 308 Private repo #1 --------------- Manifest Size: limit | none | 1000 ------------|-----------------|--------------- no-sparse | 33 725 285 081 | 33 724 834 190 sparse | 350 542 420 | 423 470 579 Manifest Chain length data limit || none || 1000 value || average | max || average | max ------------||---------|---------||---------|--------- no-sparse || 282 | 8 885 || 113 | 1 000 snapshot || 3 655 | 8 951 || 530 | 1 000 Full Store Size limit | none | 1000 ------------|----------------|--------------- no-sparse | 41 544 149 652 | 41 543 698 761 sparse | 8 448 037 300 | 8 520 965 459 Effect on speed: ================ Performances are strongly impacted by the delta chain length. Longer chain results in slower revision restoration. For this reason, the 1000 chain limit introduced by sparse-revlog helps repository with previously large chains a lot. In our corpus, this means `netbeans` and `mozilla-central` who suffered from unreasonable manifest delta chain length. Another way sparse revlog helps, is by producing better delta's. For repositories with many branches, the pathological patterns that resulted in many sub-optimal deltas are gone. Smaller delta help with operations where deltas are directly relevant, like bundle. However, the sparse-revlog logic introduces some extra processing and a more throughout testing of possible delta candidates. Adding an extra cost in some cases. This cost is usually counterbalanced by the other performance gain. However, for smaller repositories not affected by delta chain length issues or branching related issues, this might make things a bit slower. However, these are also repository where revlog performance is dwarfed by other costs. Below are the summary of some timing from the performance test suite running at `http://perf.octobus.net/` for a handful of key commands and operation. It is important to keep in mind that most of this command works on the tip part of the repository. The non-sparse and sparse version produce different delta chains and the tip revision can end up at an arbitrary point of these chains. This will impact some performance number listed in this summary. For the record: here is the delta chain length for the tip revision of manifest log in the benchmarked repository: | no-sparse | sparse | mercurial | 94 | 904 | pypy | 23 | 673 | netbeans | 4158 | 258 | mozilla | 63263 | 781 | As you can see, the chain length for mercurial and pypy turn out to be significantly longer. The netbeans and mozilla one get shorter because these repositories benefit from the maximum chain length. Timing for `hg commit`: ----------------------- The time taken by `hg commit` does not varies significantly, no drawback for using sparse here. | no-sparse | sparse | mercurial | 68.1ms | 66.7ms | pypy | 95.0ms | 94.1ms | netbeans | 614.0ms | 611.0ms | mozilla | 1340.0ms | 1.320.0ms | Check the final section for statistics on a wider array of write. Timing for bundling 10 000 changesets ------------------------------------- The repository that benefits from better delta see a good performance boost. The other ones are not significantly affected. | no-sparse | sparse | mercurial | 3.1s | 3.0s | pypy | 25.1s | 7.5s | netbeans | 24.2s | 17.0s | mozilla | 23.7s | 25.0s | Timing for unbundling 1 000 changesets -------------------------------------- Mercurial and mozilla are unaffected. The pypy repository benefit well from the better delta. However, the netbeans repository takes a visible hit. Digging that difference reveals that it comes from the sparse-revlog bundle having to deal with a snapshot that was re-encoded in the bundle. The slow path for adding new a revision had to be triggered for it, slowing things down. The Sparse versions do not have such snapshot to handle similar cases in the tested configuration. | no-sparse | sparse | mercurial | 519ms | 502ms | pypy | 1.270ms | 886ms | netbeans | 1.370ms | 2.250ms | mozilla | 3.230ms | 3.210ms | Netbeans benefits from the better deltas in other dimensions too. For example, the produced bundle is significantly smaller: * netbeans-no-sparse.hg: 2.3MB * netbeans-sparse.hg: 1.9MB Timing to restore the tip most manifest entry: ---------------------------------------------- Nothing surprising here. The timing for mercurial and pypy are within a small range where they won't affect performance much. In our tested case, they are slower as they use a longer chain. Timing for netbeans and mozilla improves a lot. Removing a significant amount of time. | no-sparse | sparse | mercurial | 1.09ms | 3.15ms | pypy | 4.11ms | 10.70ms | netbeans | 239.00ms | 112.00ms | mozilla | 688.00ms | 198.00ms | Reading 100 revision in descending order: ----------------------------------------- We see the same kind of effect when reading the last 100 revisions. Large boost for netbeans and mozilla, as they use much smaller delta chain. Mercurial and pypy longer chain means slower reads, but nothing gets out of control. | no-sparse | sparse | mercurial | 0.089s | 0.268s | pypy | 0.259s | 0.698s | netbeans | 125.000s | 20.600s | mozilla | 23.000s | 11.400s | Writing from full text: statistic for the last 30K revisions ------------------------------------------------------------ This benchmark adds revisions to revlog from their full text. This is similar to the work done during a commit, but for a large amount of revisions so that we get a more relevant view. We see better overall performances with sparse-revlog. The very worst case is usually slower with sparse-revlog, but does not gets out of control. For the vast majorities of the other writes, sparse-revlog is significantly faster for larger repositories. This is reflected in the accumulated rewrite time for netbeans and mozilla. The notable exception is the pypy repository where things get slower. The extra processing is not balanced by shorter delta chain. However, this is to be seen as a blocking issue. First, the overall time spend dealing with revlog for the repository pypy size is small compared to the other costs, so we get slower on operations that matter less than for other larger repository. Second, we still get nice size benefit from using sparse-revlog, smaller repo size brings other usability and speed benefit (eg: bundle size). max time | no-sparse | sparse | mercurial | 0.010143s | 0.045280s | pypy | 0.034924s | 0.243288s | netbeans | 0.605371s | 2.130876s | mozilla | 1.478342s | 3.424541s | 99% time | no-sparse | sparse | mercurial | 0.003774s | 0.003758s | pypy | 0.017387s | 0.025310s | netbeans | 0.576913s | 0.271195s | mozilla | 1.478342s | 0.449661s | 95% time | no-sparse | sparse | mercurial | 0.002069s | 0.002120s | pypy | 0.010141s | 0.014797s | netbeans | 0.540202s | 0.258644s | mozilla | 0.654830s | 0.243440s | full time | no-sparse | sparse | mercurial | 14.15s | 14.87s | pypy | 90.50s | 137.12s | netbeans | 6401.06s | 3411.14s | mozilla | 3086.89s | 1991.97s | Differential Revision: https://phab.mercurial-scm.org/D5345

test: preemptively disable sparse-revlog for some of test-upgrade-repo Some part of this test assumes sparse-revlog is off. We enforce it explicitly. Differential Revision: https://phab.mercurial-scm.org/D5344

test: enable sparse-revlog for test-wireproto-content-redirects.t We are about to enable sparse-revlog globally. To help with reviewing the tests change, we isolate them in individual changesets. Differential Revision: https://phab.mercurial-scm.org/D5343

test: enable sparse-revlog for test-wireproto-command-capabilities.t We are about to enable sparse-revlog globally. To help with reviewing the tests change, we isolate them in individual changesets. Differential Revision: https://phab.mercurial-scm.org/D5342