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We add the ability to filter the object types in the path-walk API so
the callback function is called fewer times.
This adds the ability to ask for the commits in a list, as well. We
re-use the empty string for this set of objects because these are passed
directly to the callback function instead of being part of the
'path_stack'.
Future changes will add the ability to visit annotated tags.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Add some tests based on the current behavior, doing interesting checks
for different sets of branches, ranges, and the --boundary option. This
sets a baseline for the behavior and we can extend it as new options are
introduced.
Store and output a 'batch_nr' value so we can demonstrate that the paths are
grouped together in a batch and not following some other ordering. This
allows us to test the depth-first behavior of the path-walk API. However, we
purposefully do not test the order of the objects in the batch, so the
output is compared to the expected output through a sort.
It is important to mention that the behavior of the API will change soon as
we start to handle UNINTERESTING objects differently, but these tests will
demonstrate the change in behavior.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In anticipation of a few planned applications, introduce the most basic form
of a path-walk API. It currently assumes that there are no UNINTERESTING
objects, and does not include any complicated filters. It calls a function
pointer on groups of tree and blob objects as grouped by path. This only
includes objects the first time they are discovered, so an object that
appears at multiple paths will not be included in two batches.
These batches are collected in 'struct type_and_oid_list' objects, which
store an object type and an oid_array of objects.
The data structures are documented in 'struct path_walk_context', but in
summary the most important are:
* 'paths_to_lists' is a strmap that connects a path to a
type_and_oid_list for that path. To avoid conflicts in path names,
we make sure that tree paths end in "/" (except the root path with
is an empty string) and blob paths do not end in "/".
* 'path_stack' is a string list that is added to in an append-only
way. This stores the stack of our depth-first search on the heap
instead of using recursion.
* 'path_stack_pushed' is a strmap that stores path names that were
already added to 'path_stack', to avoid repeating paths in the
stack. Mostly, this saves us from quadratic lookups from doing
unsorted checks into the string_list.
The coupling of 'path_stack' and 'path_stack_pushed' is protected by the
push_to_stack() method. Call this instead of inserting into these
structures directly.
The walk_objects_by_path() method initializes these structures and
starts walking commits from the given rev_info struct. The commits are
used to find the list of root trees which populate the start of our
depth-first search.
The core of our depth-first search is in a while loop that continues
while we have not indicated an early exit and our 'path_stack' still has
entries in it. The loop body pops a path off of the stack and "visits"
the path via the walk_path() method.
The walk_path() method gets the list of OIDs from the 'path_to_lists'
strmap and executes the callback method on that list with the given path
and type. If the OIDs correspond to tree objects, then iterate over all
trees in the list and run add_children() to add the child objects to
their own lists, adding new entries to the stack if necessary.
In testing, this depth-first search approach was the one that used the
least memory while iterating over the object lists. There is still a
chance that repositories with too-wide path patterns could cause memory
pressure issues. Limiting the stack size could be done in the future by
limiting how many objects are being considered in-progress, or by
visiting blob paths earlier than trees.
There are many future adaptations that could be made, but they are left for
future updates when consumers are ready to take advantage of those features.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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We're contemplating whether to eventually replace our build systems with
a build system that is easier to use. Add a comparison of build systems
to our technical documentation as a baseline for discussion.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The `technical/repository-version.txt` document originally served as the
master list for extensions, requiring that any new extensions be defined
there. However, the `config/extensions.txt` file was introduced later
and has since become the de facto location for describing extensions,
with several extensions listed there but missing from
`repository-version.txt`.
This consolidates all extension definitions into `config/extensions.txt`,
making it the authoritative source for extensions. The references in
`repository-version.txt` are updated to point to `config/extensions.txt`,
and cross-references to related documentation such as
`gitrepository-layout[5]` and `git-config[1]` are added.
Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Caleb White <cdwhite3@pm.me>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
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These links should point to `.html` files, not to `.txt` ones.
Compare also to 4945f046c7f (api docs: link to html version of
api-trace2, 2022-09-16).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Fix a typo in documentation.
Signed-off-by: Andrew Kreimer <algonell@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Import clar unit tests framework libgit2 folks invented for our
use.
* ps/clar-unit-test:
Makefile: rename clar-related variables to avoid confusion
clar: add CMake support
t/unit-tests: convert ctype tests to use clar
t/unit-tests: convert strvec tests to use clar
t/unit-tests: implement test driver
Makefile: wire up the clar unit testing framework
Makefile: do not use sparse on third-party sources
Makefile: make hdr-check depend on generated headers
Makefile: fix sparse dependency on GENERATED_H
clar: stop including `shellapi.h` unnecessarily
clar(win32): avoid compile error due to unused `fs_copy()`
clar: avoid compile error with mingw-w64
t/clar: fix compatibility with NonStop
t: import the clar unit testing framework
t: do not pass GIT_TEST_OPTS to unit tests with prove
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Our unit testing framework is a homegrown solution. While it supports
most of our needs, it is likely that the volume of unit tests will grow
quite a bit in the future such that we can exercise low-level subsystems
directly. This surfaces several shortcomings that the current solution
has:
- There is no way to run only one specific tests. While some of our
unit tests wire this up manually, others don't. In general, it
requires quite a bit of boilerplate to get this set up correctly.
- Failures do not cause a test to stop execution directly. Instead,
the test author needs to return manually whenever an assertion
fails. This is rather verbose and is not done correctly in most of
our unit tests.
- Wiring up a new testcase requires both implementing the test
function and calling it in the respective test suite's main
function, which is creating code duplication.
We can of course fix all of these issues ourselves, but that feels
rather pointless when there are already so many unit testing frameworks
out there that have those features.
We line out some requirements for any unit testing framework in
"Documentation/technical/unit-tests.txt". The "clar" unit testing
framework, which isn't listed in that table yet, ticks many of the
boxes:
- It is licensed under ISC, which is compatible.
- It is easily vendorable because it is rather tiny at around 1200
lines of code.
- It is easily hackable due to the same reason.
- It has TAP support.
- It has skippable tests.
- It preprocesses test files in order to extract test functions, which
then get wired up automatically.
While it's not perfect, the fact that clar originates from the libgit2
project means that it should be rather easy for us to collaborate with
upstream to plug any gaps.
Import the clar unit testing framework at commit 1516124 (Merge pull
request #97 from pks-t/pks-whitespace-fixes, 2024-08-15). The framework
will be wired up in subsequent commits.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The trace2 event target does not have an implementation for
trace2_printf(). While the event target is for structured events, and
trace2_printf() is for unstructured, human-readable messages, it may
still be useful to wrap these unstructured messages in a structured JSON
object. Among other things, it may reduce confusion when manually
debugging using event trace data.
Add a simple implementation for the event target that wraps
trace2_printf() messages in a minimal JSON object. Document this in
Documentation/technical/api-trace2.txt, and bump the event format
version since we're adding a new event type.
Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Incremental updates of multi-pack index files.
* tb/incremental-midx-part-1:
midx: implement support for writing incremental MIDX chains
t/t5313-pack-bounds-checks.sh: prepare for sub-directories
t: retire 'GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP'
midx: implement verification support for incremental MIDXs
midx: support reading incremental MIDX chains
midx: teach `midx_fanout_add_midx_fanout()` about incremental MIDXs
midx: teach `midx_preferred_pack()` about incremental MIDXs
midx: teach `midx_contains_pack()` about incremental MIDXs
midx: remove unused `midx_locate_pack()`
midx: teach `fill_midx_entry()` about incremental MIDXs
midx: teach `nth_midxed_offset()` about incremental MIDXs
midx: teach `bsearch_midx()` about incremental MIDXs
midx: introduce `bsearch_one_midx()`
midx: teach `nth_bitmapped_pack()` about incremental MIDXs
midx: teach `nth_midxed_object_oid()` about incremental MIDXs
midx: teach `prepare_midx_pack()` about incremental MIDXs
midx: teach `nth_midxed_pack_int_id()` about incremental MIDXs
midx: add new fields for incremental MIDX chains
Documentation: describe incremental MIDX format
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Prepare to implement incremental multi-pack indexes (MIDXs) over the
next several commits by first describing the relevant prerequisites
(like a new chunk in the MIDX format, the directory structure for
incremental MIDXs, etc.)
The format is described in detail in the patch contents below, but the
high-level description is as follows.
Incremental MIDXs live in $GIT_DIR/objects/pack/multi-pack-index.d, and
each `*.midx` within that directory has a single "parent" MIDX, which is
the MIDX layer immediately before it in the MIDX chain. The chain order
resides in a file 'multi-pack-index-chain' in the same directory.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Supporting many platforms is only possible when we have the right tools to
ensure that support.
Teach platform maintainers how they can help us to help them, by
explaining what kind of tooling support we would like to have, and what
level of support becomes available as a result. Provide examples so that
platform maintainers can see what we're asking for in practice.
With this policy in place, we can make changes with stronger assurance
that we are not breaking anybody we promised not to. Instead, we can
feel confident that our existing testing and integration practices
protect those who care from breakage.
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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While investigating a benign Coverity warning on the new pseudo-merge
implementation, I was struggling to understand the (paraphrased) below:
ofs = index_end - 24 - (index->pseudo_merges.nr * sizeof(uint64_t));
for (i = 0; i < index->pseudo_merges.nr; i++) {
index->pseudo_merges.v[i].at = get_be64(ofs);
ofs += sizeof(uint64_t);
}
, in pack-bitmap.c::load_bitmap_header(). Looking at the documentation,
the diagram describing the on-disk format (prior to this patch)
suggested that the optional extended lookup table immediately preceded
the trailing metadata portion.
If that were the case, that would make the above code from
load_bitmap_header() incorrect, as we'd be blindly reading into the
extended offset table.
But later on in the documentation there is a description of the
pseudo-merge position table as immediately preceding the trailing
metadata portion of the extension. And indeed, we do write the position
table in pack-bitmap-write.c:
/* write positions for all pseudo merges */
for (i = 0; i < writer->pseudo_merges_nr; i++)
hashwrite_be64(f, pseudo_merge_ofs[i]);
hashwrite_be32(f, writer->pseudo_merges_nr);
hashwrite_be32(f, kh_size(writer->pseudo_merge_commits));
hashwrite_be64(f, table_start - start);
hashwrite_be64(f, hashfile_total(f) - start + sizeof(uint64_t));
So this is purely a case of the diagram being out of sync with the
textual description and actual implementation of the format
specification.
Add the missing component back to the format diagram to avoid further
confusion in this area.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Prepare to implement pseudo-merge bitmaps over the next several commits
by first describing the serialization format which will store the new
pseudo-merge bitmaps themselves.
This format is implemented as an optional extension within the bitmap v1
format, making it compatible with previous versions of Git, as well as
the original .bitmap implementation within JGit.
The format is described in detail in the patch contents below, but the
high-level description is as follows:
- An array of pseudo-merge bitmaps, each containing a pair of EWAH
bitmaps: one describing the set of pseudo-merge "parents", and
another describing the set of object(s) reachable from those
parents.
- A lookup table to determine which pseudo-merge(s) a given commit
appears in. An optional extended lookup table follows when there is
at least one commit which appears in multiple pseudo-merge groups.
- Trailing metadata, including the number of pseudo-merge(s), number
of unique parents, the offset within the .bitmap file for the
pseudo-merge commit lookup table, and the size of the optional
extension itself.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Due to scalability issues, Shawn Pearce has originally proposed a new
"reftable" format more than six years ago [1]. Initially, this new
format was implemented in JGit with promising results. Around two years
ago, we have then added the "reftable" library to the Git codebase via
a4bbd13be3 (Merge branch 'hn/reftable', 2021-12-15). With this we have
landed all the low-level code to read and write reftables. Notably
missing though was the integration of this low-level code into the Git
code base in the form of a new ref backend that ties all of this
together.
This gap is now finally closed by introducing a new "reftable" backend
into the Git codebase. This new backend promises to bring some notable
improvements to Git repositories:
- It becomes possible to do truly atomic writes where either all refs
are committed to disk or none are. This was not possible with the
"files" backend because ref updates were split across multiple loose
files.
- The disk space required to store many refs is reduced, both compared
to loose refs and packed-refs. This is enabled both by the reftable
format being a binary format, which is more compact, and by prefix
compression.
- We can ignore filesystem-specific behaviour as ref names are not
encoded via paths anymore. This means there is no need to handle
case sensitivity on Windows systems or Unicode precomposition on
macOS.
- There is no need to rewrite the complete refdb anymore every time a
ref is being deleted like it was the case for packed-refs. This
means that ref deletions are now constant time instead of scaling
linearly with the number of refs.
- We can ignore file/directory conflicts so that it becomes possible
to store both "refs/heads/foo" and "refs/heads/foo/bar".
- Due to this property we can retain reflogs for deleted refs. We have
previously been deleting reflogs together with their refs to avoid
file/directory conflicts, which is not necessary anymore.
- We can properly enumerate all refs. With the "files" backend it is
not easily possible to distinguish between refs and non-refs because
they may live side by side in the gitdir.
Not all of these improvements are realized with the current "reftable"
backend implementation. At this point, the new backend is supposed to be
a drop-in replacement for the "files" backend that is used by basically
all Git repositories nowadays. It strives for 1:1 compatibility, which
means that a user can expect the same behaviour regardless of whether
they use the "reftable" backend or the "files" backend for most of the
part.
Most notably, this means we artificially limit the capabilities of the
"reftable" backend to match the limits of the "files" backend. It is not
possible to create refs that would end up with file/directory conflicts,
we do not retain reflogs, we perform stricter-than-necessary checks.
This is done intentionally due to two main reasons:
- It makes it significantly easier to land the "reftable" backend as
tests behave the same. It would be tough to argue for each and every
single test that doesn't pass with the "reftable" backend.
- It ensures compatibility between repositories that use the "files"
backend and repositories that use the "reftable" backend. Like this,
hosters can migrate their repositories to use the "reftable" backend
without causing issues for clients that use the "files" backend in
their clones.
It is expected that these artificial limitations may eventually go away
in the long term.
Performance-wise things very much depend on the actual workload. The
following benchmarks compare the "files" and "reftable" backends in the
current version:
- Creating N refs in separate transactions shows that the "files"
backend is ~50% faster. This is not surprising given that creating a
ref only requires us to create a single loose ref. The "reftable"
backend will also perform auto compaction on updates. In real-world
workloads we would likely also want to perform pack loose refs,
which would likely change the picture.
Benchmark 1: update-ref: create refs sequentially (refformat = files, refcount = 1)
Time (mean ± σ): 2.1 ms ± 0.3 ms [User: 0.6 ms, System: 1.7 ms]
Range (min … max): 1.8 ms … 4.3 ms 133 runs
Benchmark 2: update-ref: create refs sequentially (refformat = reftable, refcount = 1)
Time (mean ± σ): 2.7 ms ± 0.1 ms [User: 0.6 ms, System: 2.2 ms]
Range (min … max): 2.4 ms … 2.9 ms 132 runs
Benchmark 3: update-ref: create refs sequentially (refformat = files, refcount = 1000)
Time (mean ± σ): 1.975 s ± 0.006 s [User: 0.437 s, System: 1.535 s]
Range (min … max): 1.969 s … 1.980 s 3 runs
Benchmark 4: update-ref: create refs sequentially (refformat = reftable, refcount = 1000)
Time (mean ± σ): 2.611 s ± 0.013 s [User: 0.782 s, System: 1.825 s]
Range (min … max): 2.597 s … 2.622 s 3 runs
Benchmark 5: update-ref: create refs sequentially (refformat = files, refcount = 100000)
Time (mean ± σ): 198.442 s ± 0.241 s [User: 43.051 s, System: 155.250 s]
Range (min … max): 198.189 s … 198.670 s 3 runs
Benchmark 6: update-ref: create refs sequentially (refformat = reftable, refcount = 100000)
Time (mean ± σ): 294.509 s ± 4.269 s [User: 104.046 s, System: 190.326 s]
Range (min … max): 290.223 s … 298.761 s 3 runs
- Creating N refs in a single transaction shows that the "files"
backend is significantly slower once we start to write many refs.
The "reftable" backend only needs to update two files, whereas the
"files" backend needs to write one file per ref.
Benchmark 1: update-ref: create many refs (refformat = files, refcount = 1)
Time (mean ± σ): 1.9 ms ± 0.1 ms [User: 0.4 ms, System: 1.4 ms]
Range (min … max): 1.8 ms … 2.6 ms 151 runs
Benchmark 2: update-ref: create many refs (refformat = reftable, refcount = 1)
Time (mean ± σ): 2.5 ms ± 0.1 ms [User: 0.7 ms, System: 1.7 ms]
Range (min … max): 2.4 ms … 3.4 ms 148 runs
Benchmark 3: update-ref: create many refs (refformat = files, refcount = 1000)
Time (mean ± σ): 152.5 ms ± 5.2 ms [User: 19.1 ms, System: 133.1 ms]
Range (min … max): 148.5 ms … 167.8 ms 15 runs
Benchmark 4: update-ref: create many refs (refformat = reftable, refcount = 1000)
Time (mean ± σ): 58.0 ms ± 2.5 ms [User: 28.4 ms, System: 29.4 ms]
Range (min … max): 56.3 ms … 72.9 ms 40 runs
Benchmark 5: update-ref: create many refs (refformat = files, refcount = 1000000)
Time (mean ± σ): 152.752 s ± 0.710 s [User: 20.315 s, System: 131.310 s]
Range (min … max): 152.165 s … 153.542 s 3 runs
Benchmark 6: update-ref: create many refs (refformat = reftable, refcount = 1000000)
Time (mean ± σ): 51.912 s ± 0.127 s [User: 26.483 s, System: 25.424 s]
Range (min … max): 51.769 s … 52.012 s 3 runs
- Deleting a ref in a fully-packed repository shows that the "files"
backend scales with the number of refs. The "reftable" backend has
constant-time deletions.
Benchmark 1: update-ref: delete ref (refformat = files, refcount = 1)
Time (mean ± σ): 1.7 ms ± 0.1 ms [User: 0.4 ms, System: 1.2 ms]
Range (min … max): 1.6 ms … 2.1 ms 316 runs
Benchmark 2: update-ref: delete ref (refformat = reftable, refcount = 1)
Time (mean ± σ): 1.8 ms ± 0.1 ms [User: 0.4 ms, System: 1.3 ms]
Range (min … max): 1.7 ms … 2.1 ms 294 runs
Benchmark 3: update-ref: delete ref (refformat = files, refcount = 1000)
Time (mean ± σ): 2.0 ms ± 0.1 ms [User: 0.5 ms, System: 1.4 ms]
Range (min … max): 1.9 ms … 2.5 ms 287 runs
Benchmark 4: update-ref: delete ref (refformat = reftable, refcount = 1000)
Time (mean ± σ): 1.9 ms ± 0.1 ms [User: 0.5 ms, System: 1.3 ms]
Range (min … max): 1.8 ms … 2.1 ms 217 runs
Benchmark 5: update-ref: delete ref (refformat = files, refcount = 1000000)
Time (mean ± σ): 229.8 ms ± 7.9 ms [User: 182.6 ms, System: 46.8 ms]
Range (min … max): 224.6 ms … 245.2 ms 6 runs
Benchmark 6: update-ref: delete ref (refformat = reftable, refcount = 1000000)
Time (mean ± σ): 2.0 ms ± 0.0 ms [User: 0.6 ms, System: 1.3 ms]
Range (min … max): 2.0 ms … 2.1 ms 3 runs
- Listing all refs shows no significant advantage for either of the
backends. The "files" backend is a bit faster, but not by a
significant margin. When repositories are not packed the "reftable"
backend outperforms the "files" backend because the "reftable"
backend performs auto-compaction.
Benchmark 1: show-ref: print all refs (refformat = files, refcount = 1, packed = true)
Time (mean ± σ): 1.6 ms ± 0.1 ms [User: 0.4 ms, System: 1.1 ms]
Range (min … max): 1.5 ms … 2.0 ms 1729 runs
Benchmark 2: show-ref: print all refs (refformat = reftable, refcount = 1, packed = true)
Time (mean ± σ): 1.6 ms ± 0.1 ms [User: 0.4 ms, System: 1.1 ms]
Range (min … max): 1.5 ms … 1.8 ms 1816 runs
Benchmark 3: show-ref: print all refs (refformat = files, refcount = 1000, packed = true)
Time (mean ± σ): 4.3 ms ± 0.1 ms [User: 0.9 ms, System: 3.3 ms]
Range (min … max): 4.1 ms … 4.6 ms 645 runs
Benchmark 4: show-ref: print all refs (refformat = reftable, refcount = 1000, packed = true)
Time (mean ± σ): 4.5 ms ± 0.2 ms [User: 1.0 ms, System: 3.3 ms]
Range (min … max): 4.2 ms … 5.9 ms 643 runs
Benchmark 5: show-ref: print all refs (refformat = files, refcount = 1000000, packed = true)
Time (mean ± σ): 2.537 s ± 0.034 s [User: 0.488 s, System: 2.048 s]
Range (min … max): 2.511 s … 2.627 s 10 runs
Benchmark 6: show-ref: print all refs (refformat = reftable, refcount = 1000000, packed = true)
Time (mean ± σ): 2.712 s ± 0.017 s [User: 0.653 s, System: 2.059 s]
Range (min … max): 2.692 s … 2.752 s 10 runs
Benchmark 7: show-ref: print all refs (refformat = files, refcount = 1, packed = false)
Time (mean ± σ): 1.6 ms ± 0.1 ms [User: 0.4 ms, System: 1.1 ms]
Range (min … max): 1.5 ms … 1.9 ms 1834 runs
Benchmark 8: show-ref: print all refs (refformat = reftable, refcount = 1, packed = false)
Time (mean ± σ): 1.6 ms ± 0.1 ms [User: 0.4 ms, System: 1.1 ms]
Range (min … max): 1.4 ms … 2.0 ms 1840 runs
Benchmark 9: show-ref: print all refs (refformat = files, refcount = 1000, packed = false)
Time (mean ± σ): 13.8 ms ± 0.2 ms [User: 2.8 ms, System: 10.8 ms]
Range (min … max): 13.3 ms … 14.5 ms 208 runs
Benchmark 10: show-ref: print all refs (refformat = reftable, refcount = 1000, packed = false)
Time (mean ± σ): 4.5 ms ± 0.2 ms [User: 1.2 ms, System: 3.3 ms]
Range (min … max): 4.3 ms … 6.2 ms 624 runs
Benchmark 11: show-ref: print all refs (refformat = files, refcount = 1000000, packed = false)
Time (mean ± σ): 12.127 s ± 0.129 s [User: 2.675 s, System: 9.451 s]
Range (min … max): 11.965 s … 12.370 s 10 runs
Benchmark 12: show-ref: print all refs (refformat = reftable, refcount = 1000000, packed = false)
Time (mean ± σ): 2.799 s ± 0.022 s [User: 0.735 s, System: 2.063 s]
Range (min … max): 2.769 s … 2.836 s 10 runs
- Printing a single ref shows no real difference between the "files"
and "reftable" backends.
Benchmark 1: show-ref: print single ref (refformat = files, refcount = 1)
Time (mean ± σ): 1.5 ms ± 0.1 ms [User: 0.4 ms, System: 1.0 ms]
Range (min … max): 1.4 ms … 1.8 ms 1779 runs
Benchmark 2: show-ref: print single ref (refformat = reftable, refcount = 1)
Time (mean ± σ): 1.6 ms ± 0.1 ms [User: 0.4 ms, System: 1.1 ms]
Range (min … max): 1.4 ms … 2.5 ms 1753 runs
Benchmark 3: show-ref: print single ref (refformat = files, refcount = 1000)
Time (mean ± σ): 1.5 ms ± 0.1 ms [User: 0.3 ms, System: 1.1 ms]
Range (min … max): 1.4 ms … 1.9 ms 1840 runs
Benchmark 4: show-ref: print single ref (refformat = reftable, refcount = 1000)
Time (mean ± σ): 1.6 ms ± 0.1 ms [User: 0.4 ms, System: 1.1 ms]
Range (min … max): 1.5 ms … 2.0 ms 1831 runs
Benchmark 5: show-ref: print single ref (refformat = files, refcount = 1000000)
Time (mean ± σ): 1.6 ms ± 0.1 ms [User: 0.4 ms, System: 1.1 ms]
Range (min … max): 1.5 ms … 2.1 ms 1848 runs
Benchmark 6: show-ref: print single ref (refformat = reftable, refcount = 1000000)
Time (mean ± σ): 1.6 ms ± 0.1 ms [User: 0.4 ms, System: 1.1 ms]
Range (min … max): 1.5 ms … 2.1 ms 1762 runs
So overall, performance depends on the usecases. Except for many
sequential writes the "reftable" backend is roughly on par or
significantly faster than the "files" backend though. Given that the
"files" backend has received 18 years of optimizations by now this can
be seen as a win. Furthermore, we can expect that the "reftable" backend
will grow faster over time when attention turns more towards
optimizations.
The complete test suite passes, except for those tests explicitly marked
to require the REFFILES prerequisite. Some tests in t0610 are marked as
failing because they depend on still-in-flight bug fixes. Tests can be
run with the new backend by setting the GIT_TEST_DEFAULT_REF_FORMAT
environment variable to "reftable".
There is a single known conceptual incompatibility with the dumb HTTP
transport. As "info/refs" SHOULD NOT contain the HEAD reference, and
because the "HEAD" file is not valid anymore, it is impossible for the
remote client to figure out the default branch without changing the
protocol. This shortcoming needs to be handled in a subsequent patch
series.
As the reftable library has already been introduced a while ago, this
commit message will not go into the details of how exactly the on-disk
format works. Please refer to our preexisting technical documentation at
Documentation/technical/reftable for this.
[1]: https://public-inbox.org/git/CAJo=hJtyof=HRy=2sLP0ng0uZ4=S-DpZ5dR1aF+VHVETKG20OQ@mail.gmail.com/
Original-idea-by: Shawn Pearce <spearce@spearce.org>
Based-on-patch-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Introduce a new "extensions.refStorage" extension that allows us to
specify the ref storage format used by a repository. For now, the only
supported format is the "files" format, but this list will likely soon
be extended to also support the upcoming "reftable" format.
There have been discussions on the Git mailing list in the past around
how exactly this extension should look like. One alternative [1] that
was discussed was whether it would make sense to model the extension in
such a way that backends are arbitrarily stackable. This would allow for
a combined value of e.g. "loose,packed-refs" or "loose,reftable", which
indicates that new refs would be written via "loose" files backend and
compressed into "packed-refs" or "reftable" backends, respectively.
It is arguable though whether this flexibility and the complexity that
it brings with it is really required for now. It is not foreseeable that
there will be a proliferation of backends in the near-term future, and
the current set of existing formats and formats which are on the horizon
can easily be configured with the much simpler proposal where we have a
single value, only.
Furthermore, if we ever see that we indeed want to gain the ability to
arbitrarily stack the ref formats, then we can adapt the current
extension rather easily. Given that Git clients will refuse any unknown
value for the "extensions.refStorage" extension they would also know to
ignore a stacked "loose,packed-refs" in the future.
So let's stick with the easy proposal for the time being and wire up the
extension.
[1]: <pull.1408.git.1667846164.gitgitgadget@gmail.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Process to add some form of low-level unit tests has started.
* js/doc-unit-tests:
ci: run unit tests in CI
unit tests: add TAP unit test framework
unit tests: add a project plan document
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In our current testing environment, we spend a significant amount of
effort crafting end-to-end tests for error conditions that could easily
be captured by unit tests (or we simply forgo some hard-to-setup and
rare error conditions). Describe what we hope to accomplish by
implementing unit tests, and explain some open questions and milestones.
Discuss desired features for test frameworks/harnesses, and provide a
comparison of several different frameworks. Finally, document our
rationale for implementing a custom framework.
Co-authored-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Diff best viewed with --color-diff.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Header files cleanup.
* en/header-split-cache-h-part-3: (28 commits)
fsmonitor-ll.h: split this header out of fsmonitor.h
hash-ll, hashmap: move oidhash() to hash-ll
object-store-ll.h: split this header out of object-store.h
khash: name the structs that khash declares
merge-ll: rename from ll-merge
git-compat-util.h: remove unneccessary include of wildmatch.h
builtin.h: remove unneccessary includes
list-objects-filter-options.h: remove unneccessary include
diff.h: remove unnecessary include of oidset.h
repository: remove unnecessary include of path.h
log-tree: replace include of revision.h with simple forward declaration
cache.h: remove this no-longer-used header
read-cache*.h: move declarations for read-cache.c functions from cache.h
repository.h: move declaration of the_index from cache.h
merge.h: move declarations for merge.c from cache.h
diff.h: move declaration for global in diff.c from cache.h
preload-index.h: move declarations for preload-index.c from elsewhere
sparse-index.h: move declarations for sparse-index.c from cache.h
name-hash.h: move declarations for name-hash.c from cache.h
run-command.h: move declarations for run-command.c from cache.h
...
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A long term (but rather minor) pet-peeve of mine was the name
ll-merge.[ch]. I thought it made it harder to realize what stuff was
related to merging when I was working on the merge machinery and trying
to improve it.
Further, back in d1cbe1e6d8a ("hash-ll.h: split out of hash.h to remove
dependency on repository.h", 2023-04-22), we have split the portions of
hash.h that do not depend upon repository.h into a "hash-ll.h" (due to
the recommendation to use "ll" for "low-level" in its name[1], but which
I used as a suffix precisely because of my distaste for "ll-merge").
When we discussed adding additional "*-ll.h" files, a request was made
that we use "ll" consistently as either a prefix or a suffix. Since it
is already in use as both a prefix and a suffix, the only way to do so
is to rename some files.
Besides my distaste for the ll-merge.[ch] name, let me also note that
the files
ll-fsmonitor.h, ll-hash.h, ll-merge.h, ll-object-store.h, ll-read-cache.h
would have essentially nothing to do with each other and make no sense
to group. But giving them the common "ll-" prefix would group them. Using
"-ll" as a suffix thus seems just much more logical to me. Rename
ll-merge.[ch] to merge-ll.[ch] to achieve this consistency, and to
ensure we get a more logical grouping of files.
[1] https://lore.kernel.org/git/kl6lsfcu1g8w.fsf@chooglen-macbookpro.roam.corp.google.com/
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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These were found with an automated CLI tool [1]. Only the
"Documentation" subfolder (and not source code files) was considered
because the docs are user-facing.
[1]: https://crates.io/crates/typos-cli
Signed-off-by: Linus Arver <linusa@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The bundle-URI subsystem adds support for creation-token heuristics
to help incremental fetches.
* ds/bundle-uri-5:
bundle-uri: test missing bundles with heuristic
bundle-uri: store fetch.bundleCreationToken
fetch: fetch from an external bundle URI
bundle-uri: drop bundle.flag from design doc
clone: set fetch.bundleURI if appropriate
bundle-uri: download in creationToken order
bundle-uri: parse bundle.<id>.creationToken values
bundle-uri: parse bundle.heuristic=creationToken
t5558: add tests for creationToken heuristic
bundle: verify using check_connected()
bundle: test unbundling with incomplete history
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The Implementation Plan section lists a 'bundle.flag' option that is not
documented anywhere else. What is documented elsewhere in the document
and implemented by previous changes is the 'bundle.heuristic' config
key. For now, a heuristic is required to indicate that a bundle list is
organized for use during 'git fetch', and it is also sufficient for all
existing designs.
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Three hyphens are rendered verbatim in documentation, so "--" has to be
used to produce a dash. Fix asciidoc output for dashes. This is
similar to previous commits f0b922473e (Documentation: render special
characters correctly, 2021-07-29) and de82095a95 (doc
hash-function-transition: fix asciidoc output, 2021-02-05).
Signed-off-by: Andrei Rybak <rybak.a.v@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Design doc.
* en/sparse-checkout-design:
sparse-checkout.txt: new document with sparse-checkout directions
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Remotes are considered "promisor" if extensions.partialClone and some
other configuration variables are set. The casing for this in
Documentation/technical/repository-version.txt is not proper and may
cause confusion. This change corrects this casing.
Signed-off-by: Kousik Sanagavarapu <five231003@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
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The glossary entries for "commit-graph file" and "reachability
bitmap" have been added.
* po/glossary-around-traversal:
glossary: add reachability bitmap description
glossary: add "commit graph" description
doc: use 'object database' not ODB or abbreviation
doc: use "commit-graph" hyphenation consistently
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Once upon a time, Matheus wrote some patches to make
git grep [--cached | <REVISION>] ...
restrict its output to the sparsity specification when working in a
sparse checkout[1]. That effort got derailed by two things:
(1) The --sparse-index work just beginning which we wanted to avoid
creating conflicts for
(2) Never deciding on flag and config names and planned high level
behavior for all commands.
More recently, Shaoxuan implemented a more limited form of Matheus'
patches that only affected --cached, using a different flag name,
but also changing the default behavior in line with what Matheus did.
This again highlighted the fact that we never decided on command line
flag names, config option names, and the big picture path forward.
The --sparse-index work has been mostly complete (or at least released
into production even if some small edges remain) for quite some time
now. We have also had several discussions on flag and config names,
though we never came to solid conclusions. Stolee once upon a time
suggested putting all these into some document in
Documentation/technical[3], which Victoria recently also requested[4].
I'm behind the times, but here's a patch attempting to finally do that.
[1] https://lore.kernel.org/git/5f3f7ac77039d41d1692ceae4b0c5df3bb45b74a.1612901326.git.matheus.bernardino@usp.br/
(See his second link in that email in particular)
[2] https://lore.kernel.org/git/20220908001854.206789-2-shaoxuan.yuan02@gmail.com/
[3] https://lore.kernel.org/git/CABPp-BHwNoVnooqDFPAsZxBT9aR5Dwk5D9sDRCvYSb8akxAJgA@mail.gmail.com/
(Scroll to the very end for the final few paragraphs)
[4] https://lore.kernel.org/git/cafcedba-96a2-cb85-d593-ef47c8c8397c@github.com/
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
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The abbreviation 'ODB' is used in the technical documentation
sections for commit-graph and parallel-checkout, along with an
'odb' option in `git-pack-redundant`, without expansion.
Use 'object database' in full, in those entries. The text has not
been reflowed to keep the changes minimal.
While in the glossary for `object` terms, add the common`oid`
abbreviation to its entry.
Signed-off-by: Philip Oakley <philipoakley@iee.email>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
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Note, historical release notes have not been updated.
Signed-off-by: Philip Oakley <philipoakley@iee.email>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
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Add global counters mechanism to Trace2.
The Trace2 counters mechanism adds the ability to create a set of
global counter variables and an API to increment them efficiently.
Counters can optionally report per-thread usage in addition to the sum
across all threads.
Counter events are emitted to the Trace2 logs when a thread exits and
at process exit.
Counters are an alternative to `data` and `data_json` events.
Counters are useful when you want to measure something across the life
of the process, when you don't want per-measurement events for
performance reasons, when the data does not fit conveniently within a
region, or when your control flow does not easily let you write the
final total. For example, you might use this to report the number of
calls to unzip() or the number of de-delta steps during a checkout.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Add stopwatch timer mechanism to Trace2.
Timers are an alternative to Trace2 Regions. Regions are useful for
measuring the time spent in various computation phases, such as the
time to read the index, time to scan for unstaged files, time to scan
for untracked files, and etc.
However, regions are not appropriate in all places. For example,
during a checkout, it would be very inefficient to use regions to
measure the total time spent inflating objects from the ODB from
across the entire lifetime of the process; a per-unzip() region would
flood the output and significantly slow the command; and some form of
post-processing would be requried to compute the time spent in unzip().
Timers can be used to measure a series of timer intervals and emit
a single summary event (at thread and/or process exit).
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Eliminate the mostly obsolete `Public API` sub-section from the
`Trace2 API` section in the documentation. Strengthen the referral
to `trace2.h`.
Most of the technical information in this sub-section was moved to
`trace2.h` in 6c51cb525d (trace2: move doc to trace2.h, 2019-11-17) to
be adjacent to the function prototypes. The remaining text wasn't
that useful by itself.
Furthermore, the text would need a bit of overhaul to add routines
that do not immediately generate a message, such as stopwatch timers.
So it seemed simpler to just get rid of it.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Reduce or eliminate use of the term "TLS" in the Trace2 code.
The term "TLS" has two popular meanings: "thread-local storage" and
"transport layer security". In the Trace2 source, the term is associated
with the former. There was concern on the mailing list about it refering
to the latter.
Update the source and documentation to eliminate the use of the "TLS" term
or replace it with the phrase "thread-local storage" to reduce ambiguity.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Two documentation issues exist in the technical docs for the bundle URI
feature.
First, there is an extraneous "the" across a linebreak, making the
nonsensical phrase "the bundle the list" which should just be "the
bundle list".
Secondly, the asciidoc update treats the string "`have`s" as starting a
"<code>" block, but the second tick is interpreted as an apostrophe
instead of a closing "</code>" tag. This causes entire sentences to be
formatted as code until the next one comes along. Simply adding a space
here does not work properly as the rendered HTML keeps that space.
Instead, restructure the sentence slightly to avoid using a plural,
allowing the HTML to render correctly.
Reported-by: Philip Oakley <philipoakley@iee.email>
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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* js/typofix:
Documentation: clean up various typos in technical docs
Documentation: clean up a few misspelled word typos
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