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Add fix for extremely slow shallow clones

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Resolves: RHEL-64984
This commit is contained in:
Ondřej Pohořelský 2024-11-14 14:56:46 +01:00
parent f03a083ff0
commit 108e13eb71
3 changed files with 210 additions and 1 deletions
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115
git-2.43.0-slow-shallow-clones.patch Normal file
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@ -0,0 +1,115 @@
From 51441e6460b505c07b4a8a6deeaa7de4bf6e8e33 Mon Sep 17 00:00:00 2001
From: Junio C Hamano <gitster@pobox.com>
Date: Fri, 3 May 2024 08:34:27 -0700
Subject: [PATCH] stop using HEAD for attributes in bare repository by default
With 23865355 (attr: read attributes from HEAD when bare repo,
2023-10-13), we started to use the HEAD tree as the default
attribute source in a bare repository. One argument for such a
behaviour is that it would make things like "git archive" run in
bare and non-bare repositories for the same commit consistent.
This changes was merged to Git 2.43 but without an explicit mention
in its release notes.
It turns out that this change destroys performance of shallowly
cloning from a bare repository. As the "server" installations are
expected to be mostly bare, and "git pack-objects", which is the
core of driving the other side of "git clone" and "git fetch" wants
to see if a path is set not to delta with blobs from other paths via
the attribute system, the change forces the server side to traverse
the tree of the HEAD commit needlessly to find if each and every
paths the objects it sends out has the attribute that controls the
deltification. Given that (1) most projects do not configure such
an attribute, and (2) it is dubious for the server side to honor
such an end-user supplied attribute anyway, this was a poor choice
of the default.
To mitigate the current situation, let's revert the change that uses
the tree of HEAD in a bare repository by default as the attribute
source. This will help most people who have been happy with the
behaviour of Git 2.42 and before.
Two things to note:
* If you are stuck with versions of Git 2.43 or newer, that is
older than the release this fix appears in, you can explicitly
set the attr.tree configuration variable to point at an empty
tree object, i.e.
$ git config attr.tree 4b825dc642cb6eb9a060e54bf8d69288fbee4904
* If you like the behaviour we are reverting, you can explicitly
set the attr.tree configuration variable to HEAD, i.e.
$ git config attr.tree HEAD
The right fix for this is to optimize the code paths that allow
accesses to attributes in tree objects, but that is a much more
involved change and is left as a longer-term project, outside the
scope of this "first step" fix.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
attr.c | 7 -------
t/t0003-attributes.sh | 10 ++++++++--
t/t5001-archive-attr.sh | 3 ++-
3 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/attr.c b/attr.c
index e62876dfd3e9be..02ab8436266289 100644
--- a/attr.c
+++ b/attr.c
@@ -1213,13 +1213,6 @@ static void compute_default_attr_source(struct object_id *attr_source)
ignore_bad_attr_tree = 1;
}
- if (!default_attr_source_tree_object_name &&
- startup_info->have_repository &&
- is_bare_repository()) {
- default_attr_source_tree_object_name = "HEAD";
- ignore_bad_attr_tree = 1;
- }
-
if (!default_attr_source_tree_object_name || !is_null_oid(attr_source))
return;
diff --git a/t/t0003-attributes.sh b/t/t0003-attributes.sh
index aee2298f01331a..5de46ddf67f7ff 100755
--- a/t/t0003-attributes.sh
+++ b/t/t0003-attributes.sh
@@ -384,13 +384,19 @@ test_expect_success 'bad attr source defaults to reading .gitattributes file' '
)
'
-test_expect_success 'bare repo defaults to reading .gitattributes from HEAD' '
+test_expect_success 'bare repo no longer defaults to reading .gitattributes from HEAD' '
test_when_finished rm -rf test bare_with_gitattribute &&
git init test &&
test_commit -C test gitattributes .gitattributes "f/path test=val" &&
git clone --bare test bare_with_gitattribute &&
- echo "f/path: test: val" >expect &&
+
+ echo "f/path: test: unspecified" >expect &&
git -C bare_with_gitattribute check-attr test -- f/path >actual &&
+ test_cmp expect actual &&
+
+ echo "f/path: test: val" >expect &&
+ git -C bare_with_gitattribute -c attr.tree=HEAD \
+ check-attr test -- f/path >actual &&
test_cmp expect actual
'
diff --git a/t/t5001-archive-attr.sh b/t/t5001-archive-attr.sh
index eaf959d8f63f15..7310774af5efea 100755
--- a/t/t5001-archive-attr.sh
+++ b/t/t5001-archive-attr.sh
@@ -133,7 +133,8 @@ test_expect_success 'git archive vs. bare' '
'
test_expect_success 'git archive with worktree attributes, bare' '
- (cd bare && git archive --worktree-attributes HEAD) >bare-worktree.tar &&
+ (cd bare &&
+ git -c attr.tree=HEAD archive --worktree-attributes HEAD) >bare-worktree.tar &&
(mkdir bare-worktree && cd bare-worktree && "$TAR" xf -) <bare-worktree.tar
'

79
git-2.43.0-t6300-avoid-hard-coding-object-sizes.patch Normal file
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@ -0,0 +1,79 @@
From fbc6526ea651565889e437ce7b12c762ef858813 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ren=C3=A9=20Scharfe?= <l.s.r@web.de>
Date: Tue, 12 Dec 2023 18:04:55 +0100
Subject: [PATCH] t6300: avoid hard-coding object sizes
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
f4ee22b526 (ref-filter: add tests for objectsize:disk, 2018-12-24)
hard-coded the expected object sizes. Coincidentally the size of commit
and tag is the same with zlib at the default compression level.
1f5f8f3e85 (t6300: abstract away SHA-1-specific constants, 2020-02-22)
encoded the sizes as a single value, which coincidentally also works
with sha256.
Different compression libraries like zlib-ng may arrive at different
values. Get them from the file system instead of hard-coding them to
make switching the compression library (or changing the compression
level) easier.
Reported-by: Ondrej Pohorelsky <opohorel@redhat.com>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
t/t6300-for-each-ref.sh | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
index 00a060df0b5e81..c65c795fce2a58 100755
--- a/t/t6300-for-each-ref.sh
+++ b/t/t6300-for-each-ref.sh
@@ -20,12 +20,13 @@ setdate_and_increment () {
export GIT_COMMITTER_DATE GIT_AUTHOR_DATE
}
-test_expect_success setup '
- test_oid_cache <<-EOF &&
- disklen sha1:138
- disklen sha256:154
- EOF
+test_object_file_size () {
+ oid=$(git rev-parse "$1")
+ path=".git/objects/$(test_oid_to_path $oid)"
+ test_file_size "$path"
+}
+test_expect_success setup '
# setup .mailmap
cat >.mailmap <<-EOF &&
A Thor <athor@example.com> A U Thor <author@example.com>
@@ -94,7 +95,6 @@ test_atom () {
}
hexlen=$(test_oid hexsz)
-disklen=$(test_oid disklen)
test_atom head refname refs/heads/main
test_atom head refname: refs/heads/main
@@ -129,7 +129,7 @@ test_atom head push:strip=1 remotes/myfork/main
test_atom head push:strip=-1 main
test_atom head objecttype commit
test_atom head objectsize $((131 + hexlen))
-test_atom head objectsize:disk $disklen
+test_atom head objectsize:disk $(test_object_file_size refs/heads/main)
test_atom head deltabase $ZERO_OID
test_atom head objectname $(git rev-parse refs/heads/main)
test_atom head objectname:short $(git rev-parse --short refs/heads/main)
@@ -203,8 +203,8 @@ test_atom tag upstream ''
test_atom tag push ''
test_atom tag objecttype tag
test_atom tag objectsize $((114 + hexlen))
-test_atom tag objectsize:disk $disklen
-test_atom tag '*objectsize:disk' $disklen
+test_atom tag objectsize:disk $(test_object_file_size refs/tags/testtag)
+test_atom tag '*objectsize:disk' $(test_object_file_size refs/heads/main)
test_atom tag deltabase $ZERO_OID
test_atom tag '*deltabase' $ZERO_OID
test_atom tag objectname $(git rev-parse refs/tags/testtag)

17
git.spec
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@ -93,7 +93,7 @@
Name: git
Version: 2.43.0
Release: 1%{?rcrev}%{?dist}
Release: 2%{?rcrev}%{?dist}
Summary: Fast Version Control System
License: GPLv2
URL: https://git-scm.com/
@ -138,6 +138,16 @@ Patch4: 0002-t-lib-git-daemon-try-harder-to-find-a-port.patch
# https://github.com/tmzullinger/git/commit/aa5105dc11
Patch5: 0003-t-lib-git-svn-try-harder-to-find-a-port.patch
# attr: read attributes from HEAD when bare repo
#
# https://github.com/git/git/commit/2386535511d1181afd4e892e2a866ffe5e1d7d21
Patch6: git-2.43.0-slow-shallow-clones.patch
# t6300: avoid hard-coding object sizes
#
# https://github.com/git/git/commit/fbc6526ea651565889e437ce7b12c762ef858813
Patch7: git-2.43.0-t6300-avoid-hard-coding-object-sizes.patch
%if %{with docs}
# pod2man is needed to build Git.3pm
BuildRequires: %{_bindir}/pod2man
@ -1099,6 +1109,11 @@ rmdir --ignore-fail-on-non-empty "$testdir"
%{?with_docs:%{_pkgdocdir}/git-svn.html}
%changelog
* Thu Nov 14 2024 Ondřej Pohořelský <opohorel@redhat.com> - 2.43.0-2
- Add fix for extremely slow shallow clones
- Repair t6300 on s390x
- Resolves: RHEL-64984
* Wed Dec 06 2023 Ondřej Pohořelský <opohorel@redhat.com> - 2.43.0-1
- Update to 2.43.0
- Resolves: RHEL-17103