From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Patrick Steinhardt <ps@pks.im>
Cc: git@vger.kernel.org, "Jeff King" <peff@peff.net>,
"Felipe Contreras" <felipe.contreras@gmail.com>,
"SZEDER Gábor" <szeder.dev@gmail.com>,
"Chris Torek" <chris.torek@gmail.com>,
"Junio C Hamano" <gitster@pobox.com>,
"Taylor Blau" <me@ttaylorr.com>
Subject: Re: [PATCH v3 1/4] connected: do not sort input revisions
Date: Mon, 02 Aug 2021 14:49:29 +0200 [thread overview]
Message-ID: <871r7covsa.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <1fd83f726a04dfb5be27c74cb116618cb76be923.1627896460.git.ps@pks.im>
On Mon, Aug 02 2021, Patrick Steinhardt wrote:
> [[PGP Signed Part:Undecided]]
> 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.
Really good results:
> 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'
Just bikeshedding for a potential re-roll, perhaps --unordered-input, so
that it matches/rhymes with the existing "git cat-file --unordered",
which serves the same conceptual purpose (except this one's input, that
one's output).
next prev parent reply other threads:[~2021-08-02 12:50 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-28 5:33 [PATCH v2 0/3] Speed up connectivity checks via bitmaps Patrick Steinhardt
2021-06-28 5:33 ` [PATCH v2 1/3] p5400: add perf tests for git-receive-pack(1) Patrick Steinhardt
2021-06-28 7:49 ` Ævar Arnfjörð Bjarmason
2021-06-29 6:18 ` Patrick Steinhardt
2021-06-29 12:09 ` Ævar Arnfjörð Bjarmason
2021-06-28 5:33 ` [PATCH v2 2/3] receive-pack: skip connectivity checks on delete-only commands Patrick Steinhardt
2021-06-28 8:00 ` Ævar Arnfjörð Bjarmason
2021-06-28 8:06 ` Ævar Arnfjörð Bjarmason
2021-06-29 6:26 ` Patrick Steinhardt
2021-06-30 1:31 ` Jeff King
2021-06-30 1:35 ` Jeff King
2021-06-30 13:52 ` Patrick Steinhardt
2021-06-28 5:33 ` [PATCH v2 3/3] connected: implement connectivity check using bitmaps Patrick Steinhardt
2021-06-28 20:23 ` Taylor Blau
2021-06-29 22:44 ` Taylor Blau
2021-06-30 2:04 ` Jeff King
2021-06-30 3:07 ` Taylor Blau
2021-06-30 5:45 ` Jeff King
2021-07-02 17:44 ` Taylor Blau
2021-07-02 21:21 ` Jeff King
2021-06-30 1:51 ` Jeff King
2021-07-20 14:26 ` Patrick Steinhardt
2021-08-02 9:37 ` [PATCH v3 0/4] Speed up connectivity checks Patrick Steinhardt
2021-08-02 9:38 ` [PATCH v3 1/4] connected: do not sort input revisions Patrick Steinhardt
2021-08-02 12:49 ` Ævar Arnfjörð Bjarmason [this message]
2021-08-03 8:50 ` Patrick Steinhardt
2021-08-04 11:01 ` Ævar Arnfjörð Bjarmason
2021-08-02 19:00 ` Junio C Hamano
2021-08-03 8:55 ` Patrick Steinhardt
2021-08-03 21:47 ` Junio C Hamano
2021-08-02 9:38 ` [PATCH v3 2/4] revision: stop retrieving reference twice Patrick Steinhardt
2021-08-02 12:53 ` Ævar Arnfjörð Bjarmason
2021-08-02 9:38 ` [PATCH v3 3/4] revision: avoid loading object headers multiple times Patrick Steinhardt
2021-08-02 12:55 ` Ævar Arnfjörð Bjarmason
2021-08-05 10:12 ` Patrick Steinhardt
2021-08-02 19:40 ` Junio C Hamano
2021-08-03 9:07 ` Patrick Steinhardt
2021-08-06 14:17 ` Patrick Steinhardt
2021-08-02 9:38 ` [PATCH v3 4/4] revision: avoid hitting packfiles when commits are in commit-graph Patrick Steinhardt
2021-08-02 20:01 ` Junio C Hamano
2021-08-03 9:16 ` Patrick Steinhardt
2021-08-03 21:56 ` Junio C Hamano
2021-08-05 11:01 ` Patrick Steinhardt
2021-08-05 16:16 ` Junio C Hamano
2021-08-04 10:51 ` Ævar Arnfjörð Bjarmason
2021-08-05 11:25 ` [PATCH v4 0/6] Speed up connectivity checks Patrick Steinhardt
2021-08-05 11:25 ` [PATCH v4 1/6] revision: separate walk and unsorted flags Patrick Steinhardt
2021-08-05 18:47 ` Junio C Hamano
2021-08-05 11:25 ` [PATCH v4 2/6] connected: do not sort input revisions Patrick Steinhardt
2021-08-05 18:44 ` Junio C Hamano
2021-08-06 6:00 ` Patrick Steinhardt
2021-08-06 16:50 ` Junio C Hamano
2021-08-05 11:25 ` [PATCH v4 3/6] revision: stop retrieving reference twice Patrick Steinhardt
2021-08-05 11:25 ` [PATCH v4 4/6] revision: avoid loading object headers multiple times Patrick Steinhardt
2021-08-05 11:25 ` [PATCH v4 5/6] commit-graph: split out function to search commit position Patrick Steinhardt
2021-08-05 11:25 ` [PATCH v4 6/6] revision: avoid hitting packfiles when commits are in commit-graph Patrick Steinhardt
2021-08-09 8:00 ` [PATCH v5 0/5] Speed up connectivity checks Patrick Steinhardt
2021-08-09 8:02 ` Patrick Steinhardt
2021-08-09 8:11 ` Patrick Steinhardt
2021-08-09 8:11 ` [PATCH v5 1/5] revision: separate walk and unsorted flags Patrick Steinhardt
2021-08-09 8:11 ` [PATCH v5 2/5] connected: do not sort input revisions Patrick Steinhardt
2021-08-09 8:11 ` [PATCH v5 3/5] revision: stop retrieving reference twice Patrick Steinhardt
2021-08-09 8:11 ` [PATCH v5 4/5] commit-graph: split out function to search commit position Patrick Steinhardt
2021-08-09 8:12 ` [PATCH v5 5/5] revision: avoid hitting packfiles when commits are in commit-graph Patrick Steinhardt
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