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author | Patrick Steinhardt <ps@pks.im> | 2021-08-09 11:11:50 +0300 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2021-08-09 19:51:12 +0300 |
commit | f45022dc2fd692fd024f2eb41a86a66f19013d43 (patch) | |
tree | 8760483c0d09204dfd8d2c72101a66769ec86824 /Documentation/rev-list-options.txt | |
parent | 29ef1f27fed21b5b7d3c996a01f1364e7e841917 (diff) |
connected: do not sort input revisions
In order to compute whether objects reachable from a set of tips are all
connected, we do a revision walk with these tips as positive references
and `--not --all`. `--not --all` will cause the revision walk to load
all preexisting references as uninteresting, which can be very expensive
in repositories with many references.
Benchmarking the git-rev-list(1) command highlights that by far the most
expensive single phase is initial sorting of the input revisions: after
all references have been loaded, we first sort commits by author date.
In a real-world repository with about 2.2 million references, it makes
up about 40% of the total runtime of git-rev-list(1).
Ultimately, the connectivity check shouldn't really bother about the
order of input revisions at all. We only care whether we can actually
walk all objects until we hit the cut-off point. So sorting the input is
a complete waste of time.
Introduce a new "--unsorted-input" flag to git-rev-list(1) which will
cause it to not sort the commits and adjust the connectivity check to
always pass the flag. This results in the following speedups, executed
in a clone of gitlab-org/gitlab [1]:
Benchmark #1: git rev-list --objects --quiet --not --all --not $(cat newrev)
Time (mean ± σ): 7.639 s ± 0.065 s [User: 7.304 s, System: 0.335 s]
Range (min … max): 7.543 s … 7.742 s 10 runs
Benchmark #2: git rev-list --unsorted-input --objects --quiet --not --all --not $newrev
Time (mean ± σ): 4.995 s ± 0.044 s [User: 4.657 s, System: 0.337 s]
Range (min … max): 4.909 s … 5.048 s 10 runs
Summary
'git rev-list --unsorted-input --objects --quiet --not --all --not $(cat newrev)' ran
1.53 ± 0.02 times faster than 'git rev-list --objects --quiet --not --all --not $newrev'
[1]: https://gitlab.com/gitlab-org/gitlab.git. Note that not all refs
are visible to clients.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'Documentation/rev-list-options.txt')
-rw-r--r-- | Documentation/rev-list-options.txt | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt index 24569b06d1..b7bd27e171 100644 --- a/Documentation/rev-list-options.txt +++ b/Documentation/rev-list-options.txt @@ -968,6 +968,11 @@ list of the missing objects. Object IDs are prefixed with a ``?'' character. objects. endif::git-rev-list[] +--unsorted-input:: + Show commits in the order they were given on the command line instead + of sorting them in reverse chronological order by commit time. Cannot + be combined with `--no-walk` or `--no-walk=sorted`. + --no-walk[=(sorted|unsorted)]:: Only show the given commits, but do not traverse their ancestors. This has no effect if a range is specified. If the argument @@ -975,7 +980,8 @@ endif::git-rev-list[] given on the command line. Otherwise (if `sorted` or no argument was given), the commits are shown in reverse chronological order by commit time. - Cannot be combined with `--graph`. + Cannot be combined with `--graph`. Cannot be combined with + `--unsorted-input` if `sorted` or no argument was given. --do-walk:: Overrides a previous `--no-walk`. |