The test 1600.6 can fail under --stress due to mtime collisions. Most of
the tests include a removal of the index file to guarantee that the
index is updated. However, the submodule test addded in ee1f0c242e
(read-cache: add index.skipHash config option, 2023-01-06) did not
include this removal. Thus, on rare occasions, the test can fail because
the index still has a non-null trailing hash, as detected by the helper
added in da9acde14e (test-lib-functions: add helper for trailing hash,
2023-01-06).
By removing the submodule's index before the 'git -C sub add a' command,
we guarantee that the index is rewritten with the new index.skipHash
config option.
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The recent addition of the index.skipHash config option allows index
writes to speed up by skipping the hash computation for the trailing
checksum. This is particularly critical for repositories with many files
at HEAD, so add this config option to two cases where users in that
scenario may opt-in to such behavior:
1. The feature.manyFiles config option enables some options that are
helpful for repositories with many files at HEAD.
2. 'scalar register' and 'scalar reconfigure' set config options that
optimize for large repositories.
In both of these cases, set index.skipHash=true to gain this
speedup. Add tests that demonstrate the proper way that
index.skipHash=true can override feature.manyFiles=true.
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
It can be helpful to check that a file format with a trailing hash has a
specific hash in the final bytes of a written file. This is made more
apparent by recent changes that allow skipping the hash algorithm and
writing a null hash at the end of the file instead.
Add a new test_trailing_hash helper and use it in t1600 to verify that
index.skipHash=true really does skip the hash computation, since
'git fsck' does not actually verify the hash. This confirms that when
the config is disabled explicitly in a super project but enabled in a
submodule, then the use of repo_config_get_bool() loads config from the
correct repository in the case of 'git add'. There are other cases where
istate->repo is NULL and thus this config is loaded instead from
the_repository, but that's due to many different code paths initializing
index_state structs in their own way.
Keep the 'git fsck' call to ensure that any potential future change to
check the index hash does not cause an error in this case.
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The previous change allowed skipping the hashing portion of the
hashwrite API, using it instead as a buffered write API. Disabling the
hashwrite can be particularly helpful when the write operation is in a
critical path.
One such critical path is the writing of the index. This operation is so
critical that the sparse index was created specifically to reduce the
size of the index to make these writes (and reads) faster.
This trade-off between file stability at rest and write-time performance
is not easy to balance. The index is an interesting case for a couple
reasons:
1. Writes block users. Writing the index takes place in many user-
blocking foreground operations. The speed improvement directly
impacts their use. Other file formats are typically written in the
background (commit-graph, multi-pack-index) or are super-critical to
correctness (pack-files).
2. Index files are short lived. It is rare that a user leaves an index
for a long time with many staged changes. Outside of staged changes,
the index can be completely destroyed and rewritten with minimal
impact to the user.
Following a similar approach to one used in the microsoft/git fork [1],
add a new config option (index.skipHash) that allows disabling this
hashing during the index write. The cost is that we can no longer
validate the contents for corruption-at-rest using the trailing hash.
[1] 21fed2d914
We load this config from the repository config given by istate->repo,
with a fallback to the_repository if it is not set.
While older Git versions will not recognize the null hash as a special
case, the file format itself is still being met in terms of its
structure. Using this null hash will still allow Git operations to
function across older versions.
The one exception is 'git fsck' which checks the hash of the index file.
This used to be a check on every index read, but was split out to just
the index in a33fc72fe9 (read-cache: force_verify_index_checksum,
2017-04-14) and released first in Git 2.13.0. Document the versions that
relaxed these restrictions, with the optimistic expectation that this
change will be included in Git 2.40.0.
Here, we disable this check if the trailing hash is all zeroes. We add a
warning to the config option that this may cause undesirable behavior
with older Git versions.
As a quick comparison, I tested 'git update-index --force-write' with
and without index.skipHash=true on a copy of the Linux kernel
repository.
Benchmark 1: with hash
Time (mean ± σ): 46.3 ms ± 13.8 ms [User: 34.3 ms, System: 11.9 ms]
Range (min … max): 34.3 ms … 79.1 ms 82 runs
Benchmark 2: without hash
Time (mean ± σ): 26.0 ms ± 7.9 ms [User: 11.8 ms, System: 14.2 ms]
Range (min … max): 16.3 ms … 42.0 ms 69 runs
Summary
'without hash' ran
1.78 ± 0.76 times faster than 'with hash'
These performance benefits are substantial enough to allow users the
ability to opt-in to this feature, even with the potential confusion
with older 'git fsck' versions.
Test this new config option, both at a command-line level and within a
submodule. The confirmation is currently limited to confirm that 'git
fsck' does not complain about the index. Future updates will make this
test more robust.
It is critical that this test is placed before the test_index_version
tests, since those tests obliterate the .git/config file and hence lose
the setting from GIT_TEST_DEFAULT_HASH, if set.
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
As in 7ff24785cb (leak tests: mark some misc tests as passing with
SANITIZE=leak, 2021-10-12) continue marking various miscellaneous
tests as passing when git is compiled with SANITIZE=leak. They'll now
be listed as running under the "GIT_TEST_PASSING_SANITIZE_LEAK=true"
test mode (the "linux-leaks" CI target).
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Tests in 't1600-index.sh' check that various bogus index version
values are recognized and an appropriate warning message is issued.
GIT_TEST_SPLIT_INDEX=1 is supposed to trigger index splitting
randomly, and thus might interfere [1] with these tests: splitting the
index means that two index files are written (the shared base index
and the split '.git/index'), and the same warning message is then
issued twice, failing these tests.
Unset GIT_TEST_SPLIT_INDEX in this test script to avoid such
interference.
[1] There is no such interference at the moment, because, alas,
GIT_TEST_SPLIT_INDEX=1 is broken and never split the index. There
was no such interference in the past (before it broke) either,
because the first index write with GIT_TEST_SPLIT_INDEX=1 never
split the index, only the second write did. A subsequent commit
fixing GIT_TEST_SPLIT_INDEX will have all the details on this.
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Acked-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In a helper function in the 't1600-index.sh' test script the stderr
of a 'git add' command is redirected to its stdout, but its stdout is
not redirected anywhere. So apparently this redirection is
unnecessary, remove it.
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Acked-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
As a follow-up to d162b25f95 (tests: remove support for
GIT_TEST_GETTEXT_POISON, 2021-01-20) remove most uses of test_i18ncmp
via a simple s/test_i18ncmp/test_cmp/g search-replacement.
I'm leaving t6300-for-each-ref.sh out due to a conflict with in-flight
changes between "master" and "seen", as well as the prerequisite
itself due to other changes between "master" and "next/seen" which add
new test_i18ncmp uses.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Several config options were combined into a repo_settings struct in
ds/feature-macros, including a move of the "index.version" config
setting in 7211b9e (repo-settings: consolidate some config settings,
2019-08-13).
Unfortunately, that file looked like a lot of boilerplate and what is
clearly a factor of copy-paste overload, the config setting is parsed
with repo_config_ge_bool() instead of repo_config_get_int(). This means
that a setting "index.version=4" would not register correctly and would
revert to the default version of 3.
I caught this while incorporating v2.24.0-rc0 into the VFS for Git
codebase, where we really care that the index is in version 4.
This was not caught by the codebase because the version checks placed
in t1600-index.sh did not test the "basic" scenario enough. Here, we
modify the test to include these normal settings to not be overridden by
features.manyFiles or GIT_INDEX_VERSION. While the "default" version is
3, this is demoted to version 2 in do_write_index() when not necessary.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The feature.manyFiles setting is suitable for repos with many
files in the working directory. By setting index.version=4 and
core.untrackedCache=true, commands such as 'git status' should
improve.
While adding this setting, modify the index version precedence
tests to check how this setting overrides the default for
index.version is unset.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Using 'test_must_be_empty' is shorter and more idiomatic than
>empty &&
test_cmp empty out
as it saves the creation of an empty file. Furthermore, sometimes the
expected empty file doesn't have such a descriptive name like 'empty',
and its creation is far away from the place where it's finally used
for comparison (e.g. in 't7600-merge.sh', where two expected empty
files are created in the 'setup' test, but are used only about 500
lines later).
These cases were found by instrumenting 'test_cmp' to error out the
test script when it's used to compare empty files, and then converted
manually.
Note that even after this patch there still remain a lot of cases
where we use 'test_cmp' to check empty files:
- Sometimes the expected output is not hard-coded in the test, but
'test_cmp' is used to ensure that two similar git commands produce
the same output, and that output happens to be empty, e.g. the
test 'submodule update --merge - ignores --merge for new
submodules' in 't7406-submodule-update.sh'.
- Repetitive common tasks, including preparing the expected results
and running 'test_cmp', are often extracted into a helper
function, and some of this helper's callsites expect no output.
- For the same reason as above, the whole 'test_expect_success'
block is within a helper function, e.g. in 't3070-wildmatch.sh'.
- Or 'test_cmp' is invoked in a loop, e.g. the test 'cvs update
(-p)' in 't9400-git-cvsserver-server.sh'.
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a config variable that allows setting the default index version when
initializing a new index file. Similar to the GIT_INDEX_VERSION
environment variable this only affects new index files.
Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Respect a GIT_INDEX_VERSION environment variable, when a new index is
initialized. Setting the environment variable will not cause existing
index files to be converted to another format, but will only affect
newly written index files. This can be used to initialize repositories
with index-v4.
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
