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 --- Documentation/rev-list-options.txt | 8 +++++++- connected.c | 1 + revision.c | 9 +++++++++ t/t6000-rev-list-misc.sh | 31 ++++++++++++++++++++++++++++++ 4 files changed, 48 insertions(+), 1 deletion(-) 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`. diff --git a/connected.c b/connected.c index b18299fdf0..b5f9523a5f 100644 --- a/connected.c +++ b/connected.c @@ -106,6 +106,7 @@ int check_connected(oid_iterate_fn fn, void *cb_data, if (opt->progress) strvec_pushf(&rev_list.args, "--progress=%s", _("Checking connectivity")); + strvec_push(&rev_list.args, "--unsorted-input"); rev_list.git_cmd = 1; rev_list.env = opt->env; diff --git a/revision.c b/revision.c index 86bbcd10d2..47541407d2 100644 --- a/revision.c +++ b/revision.c @@ -2256,6 +2256,10 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg } else if (!strcmp(arg, "--author-date-order")) { revs->sort_order = REV_SORT_BY_AUTHOR_DATE; revs->topo_order = 1; + } else if (!strcmp(arg, "--unsorted-input")) { + if (revs->no_walk) + die(_("--unsorted-input is incompatible with --no-walk")); + revs->unsorted_input = 1; } else if (!strcmp(arg, "--early-output")) { revs->early_output = 100; revs->topo_order = 1; @@ -2651,8 +2655,13 @@ static int handle_revision_pseudo_opt(const char *submodule, } else if (!strcmp(arg, "--not")) { *flags ^= UNINTERESTING | BOTTOM; } else if (!strcmp(arg, "--no-walk")) { + if (!revs->no_walk && revs->unsorted_input) + die(_("--no-walk is incompatible with --unsorted-input")); revs->no_walk = 1; } else if (skip_prefix(arg, "--no-walk=", &optarg)) { + if (!revs->no_walk && revs->unsorted_input) + die(_("--no-walk is incompatible with --unsorted-input")); + /* * Detached form ("--no-walk X" as opposed to "--no-walk=X") * not allowed, since the argument is optional. diff --git a/t/t6000-rev-list-misc.sh b/t/t6000-rev-list-misc.sh index 12def7bcbf..ef849e5bc8 100755 --- a/t/t6000-rev-list-misc.sh +++ b/t/t6000-rev-list-misc.sh @@ -169,4 +169,35 @@ test_expect_success 'rev-list --count --objects' ' test_line_count = $count actual ' +test_expect_success 'rev-list --unsorted-input results in different sorting' ' + git rev-list --unsorted-input HEAD HEAD~ >first && + git rev-list --unsorted-input HEAD~ HEAD >second && + ! test_cmp first second && + sort first >first.sorted && + sort second >second.sorted && + test_cmp first.sorted second.sorted +' + +test_expect_success 'rev-list --unsorted-input incompatible with --no-walk' ' + cat >expect <<-EOF && + fatal: --no-walk is incompatible with --unsorted-input + EOF + test_must_fail git rev-list --unsorted-input --no-walk HEAD 2>error && + test_cmp expect error && + test_must_fail git rev-list --unsorted-input --no-walk=sorted HEAD 2>error && + test_cmp expect error && + test_must_fail git rev-list --unsorted-input --no-walk=unsorted HEAD 2>error && + test_cmp expect error && + + cat >expect <<-EOF && + fatal: --unsorted-input is incompatible with --no-walk + EOF + test_must_fail git rev-list --no-walk --unsorted-input HEAD 2>error && + test_cmp expect error && + test_must_fail git rev-list --no-walk=sorted --unsorted-input HEAD 2>error && + test_cmp expect error && + test_must_fail git rev-list --no-walk=unsorted --unsorted-input HEAD 2>error && + test_cmp expect error +' + test_done -- 2.32.0