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From: Patrick Steinhardt <ps@pks.im>
To: git@vger.kernel.org
Cc: "Jeff King" <peff@peff.net>,
	"Felipe Contreras" <felipe.contreras@gmail.com>,
	"SZEDER Gábor" <szeder.dev@gmail.com>,
	"Chris Torek" <chris.torek@gmail.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Junio C Hamano" <gitster@pobox.com>,
	"Taylor Blau" <me@ttaylorr.com>
Subject: [PATCH v3 0/4] Speed up connectivity checks
Date: Mon, 2 Aug 2021 11:37:57 +0200	[thread overview]
Message-ID: <cover.1627896460.git.ps@pks.im> (raw)
In-Reply-To: <cover.1624858240.git.ps@pks.im>

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Hi,

I finally found some time again to have another look at my old problem
of slow connectivity checks. After my previous two approaches of using
the quarantine directory and using bitmaps proved to not really be
viable, I've taken a step back yet again. The result is this series,
which speeds up the connectivity checks by optimizing "revison.c". More
specifically, I'm mostly tweaking how we're queueing up references,
which is the most pressing issue we've observed at GitLab when doing
connectivity checks in repos with many references.

The following optimizations are part of this series. All benchmarks were
done on [1], which is a repository with about 2.2 million references
(even though most of them are hidden to public users) with `git rev-list
--objects --quiet --unsorted-input --not --all --not $newrev`.

    1. We used to sort the input references in git-rev-list(1). This is
       moot in the context of connectivity checks, so a new flag
       suppresses this sorting. This improves the command by ~30% from
       7.6s to 4.9s.

    2. We did some busy-work, loading each reference twice via
       `get_reference()`. We now don't anymore, resulting in a ~8%
       speedup from 5.0s to 4.6s.

    3. An optimization was done to how we load objects. Previously, we
       always called `oid_object_info()`, even if we had already loaded
       the object. This was tweaked to use `lookup_unknown_object()`,
       which is a performance-memory tradeoff. This saves us another 7%,
       going from 4.7s to 4.4s, but it's a prereq for (4).

    4. We now make better use of the commit-graph in that we first try
       loading from there before we load it from the ODB. This is a 40%
       speedup, going from 4.4s to 2.8s.

The result is a speedup of about 65%. The nice thing compared to
previous versions is that this should also be visible when directly
executing git-rev-list(1) or doing a revwalk.

Patch #1 still needs some polishing if we agree that this patch series
makes sense, given that it's still missing documentation.

Patrick

[1]: https://gitlab.com/gitlab-org/gitlab.git

Patrick Steinhardt (4):
  connected: do not sort input revisions
  revision: stop retrieving reference twice
  revision: avoid loading object headers multiple times
  revision: avoid hitting packfiles when commits are in commit-graph

 commit-graph.c | 55 +++++++++++++++++++++++++++++++++++++++-----------
 commit-graph.h |  2 ++
 connected.c    |  1 +
 revision.c     | 23 ++++++++++++++++-----
 revision.h     |  1 +
 5 files changed, 65 insertions(+), 17 deletions(-)

-- 
2.32.0


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  parent reply	other threads:[~2021-08-02  9:38 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 ` Patrick Steinhardt [this message]
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
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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