* ps/setup-centralize-odb-creation:
setup: construct object database in `apply_repository_format()`
repository: stop reading loose object map twice on repo init
setup: stop initializing object database without repository
setup: stop creating the object database in `setup_git_env()`
repository: stop initializing the object database in `repo_set_gitdir()`
setup: deduplicate logic to apply repository format
setup: drop `setup_git_env()`
t0001: plug test gaps for git-init(1) with GIT_OBJECT_DIRECTORY
The documentation for `push.default = simple` has been clarified to
better explain its behavior, making it clear that it pushes the
current branch to a same-named branch on the remote, and detailing
the upstream requirements for centralized workflows.
* ib/doc-push-default-simple:
doc: clarify push.default=simple behavior
The 'git-jump' command (in contrib/) has been taught to automatically
pick a mode (merge, diff, or ws) when invoked without arguments.
* gh/jump-auto-mode:
git-jump: pick a mode automatically when invoked without arguments
Formatting object name in full hexadecimal form has been optimized
by using a new strbuf_add_oid_hex() helper function.
* rs/strbuf-add-oid-hex:
hex: add and use strbuf_add_oid_hex()
Adding a decimal integer with strbuf_addf("%u") appears commonly;
they have been optimized by using a custom formatter.
* rs/strbuf-add-uint:
ls-tree: use strbuf_add_uint()
ls-files: use strbuf_add_uint()
cat-file: use strbuf_add_uint()
strbuf: add strbuf_add_uint()
"git push" learned to take a "remote group" name to push to, which
causes pushes to multiple places, just like "git fetch" would do.
* ua/push-remote-group:
push: support pushing to a remote group
remote: move remote group resolution to remote.c
remote: fix sign-compare warnings in push_cas_option
The "promisor.quiet" configuration variable was not used from
relevant submodules when commands like "grep --recurse-submodules"
triggered a lazy fetch, which has been corrected.
* th/promisor-quiet-per-repo:
promisor-remote: fix promisor.quiet to use the correct repository
Reachability bitmap generation has been significantly optimized. By
reordering tree traversal, caching object positions, and refining how
pseudo-merge bitmaps are constructed, the performance of "git repack
--write-midx-bitmaps" is improved, especially for large repositories
and when using pseudo-merges.
* tb/bitmap-build-performance:
pack-bitmap: build pseudo-merge bitmaps after regular bitmaps
pack-bitmap: remember pseudo-merge parents
pack-bitmap: sort bitmaps before XORing
pack-bitmap: cache object positions during fill
pack-bitmap: consolidate `find_object_pos()` success path
pack-bitmap: reuse stored selected bitmaps
pack-bitmap: check subtree bits before recursing
pack-bitmap: pass object position to `fill_bitmap_tree()`
A batch of documentation pages has been updated to use the modern
synopsis style.
* ja/doc-synopsis-style-again:
doc: convert git-imap-send synopsis and options to new style
doc: convert git-apply synopsis and options to new style
doc: convert git-am synopsis and options to new style
doc: convert git-grep synopsis and options to new style
doc: git bisect: clarify the usage of the synopsis vs actual command
doc: convert git-bisect to synopsis style
The check for non-stale commits in the priority queue used by
`paint_down_to_common` and `ahead_behind` has been optimized by
replacing an O(N) scan with an O(1) counter, yielding performance
improvements in repositories with wide histories.
* kk/commit-reach-optim:
commit-reach: replace queue_has_nonstale() scan with O(1) tracking
commit-reach: deduplicate queue entries in paint_down_to_common
object.h: fix stale entries in object flag allocation table
"git stash -p" has been optimized by reusing cached index
entries in its temporary index, avoiding unnecessary lstat()
calls on unchanged files.
* aj/stash-patch-optimize-temporary-index:
stash: reuse cached index entries in --patch temporary index
'git restore --staged' has been optimized to avoid unnecessarily expanding
the sparse index when operating on paths within the sparse checkout
definition, by handling sparse directory entries at the tree level.
* ds/restore-sparse-index:
restore: avoid sparse index expansion
t1092: test 'git restore' with sparse index
The GIT_WORK_TREE variable prepared to invoke the push-to-checkout
hook was leaking into the environment even when there was no hook
used and broke the default push-to-deploy (i.e., let "git checkout"
update the working tree only when the working tree is clean).
* ar/receive-pack-worktree-env:
receive-pack: fix updateInstead with core.worktree
With the preceding changes we now always construct the repository's
object database before applying the repository format. Remove this
duplication by constructing it in `apply_repository_format()` instead.
Note that we create the object database _after_ having set up the
repository's hash algorithm, but _before_ setting the compat hash
algorithm. This is intentional:
- Constructing the object database may require knowledge of its
intended object format.
- Setting up the compatibility hash requires the object database to be
initialized already, because we immediately read the loose object
map.
The first point is sensible, the second maybe a little less so. Ideally,
it should be the responsibility of the object database itself to
initialize any data structures required for the compatibility hash. But
this would require further changes, so this is kept as-is for now.
Further note that this requires us to move handling of the environment
variables GIT_OBJECT_DIRECTORY and GIT_ALTERNATE_OBJECT_DIRECTORIES into
the repository format, as well. This allows the caller more flexibility
around whether or not those environment variables are being honored, as
we want to respect them in "setup.c", but not in "repository.c".
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When initializing a repository via `repo_init()` we end up reading the
loose object map twice:
- `apply_repository_format()` calls `repo_set_compat_hash_algo()`,
which in turn calls `repo_read_loose_object_map()` if we have a
compatibility hash configured.
- `repo_init()` calls `repo_read_loose_object_map()` directly a second
time.
Drop the second read of the loose object map in `repo_init()`.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The function `setup_git_directory_gently()` is responsible for
discovering and setting up a Git repository based on various environment
variables and the current working directory. The result is thus a fully
usable Git repository.
One oddity of this function is that we may set up the object database
even in the case where we don't have a repository, namely in the case
where the `GIT_DIR_EXPLICIT` environment variable is set but points to a
non-existent repository. If so, we call `setup_git_env_internal()` with
the value of the environment variable so that the repository's Git
directory is configured, even if it points to a non-existent directory.
Historically though, this function didn't only configure the repository,
but also initialized the object database. We retained this behaviour
from a preceding commit, even though it really doesn't make much sense
in the first place -- there is no repository, so we don't have an object
database either. There seemingly isn't much of a reason to construct the
object database, as we typically won't try to read objects when we don't
have an object database.
There's one exception though: git-index-pack(1) may run outside of a
repository, which can be used to perform consistency checks for a
packfile. The code path is _almost_ working: we already know to call
`parse_object_buffer()`, which can read objects without an object
database being available. And that works for all object types except for
commits, because `parse_commit_buffer()` calls `parse_commit_graph()`,
and that function doesn't handle the case where we don't have an object
database.
Fix this instance to check for the object database instead of checking
for the Git directory having been initialized. With this fixed, we can
now stop constructing an object database completely.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In the preceding commit we have stopped creating the object database in
`repo_set_gitdir()`. But the logic is still somewhat confusing as we
still end up creating it conditionally in `setup_git_dir()`, which is
called multiple times.
Drop the conditional logic and instead create the object database in all
places where we have discovered and configured a repository.
This leads to even more duplication than we already had in the preceding
commit, but an alert reader may notice that we now (almost) always call
`odb_new()` directly before having called `apply_repository_format()`.
The only exception to this is `setup_git_directory_gently()`, where we
also call the function when _not_ applying the repository format. This
will be fixed in the next commit, and once that's done we can then unify
creation of the object database into `apply_repository_format()`.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The function `repo_set_gitdir()` obviously sets the Git directory for a
given repository. Less obviously though, the function also configures a
couple of auxiliary settings.
One such thing is that we create the object database in this function.
This logic only happens conditionally though, as `set_git_dir()` may be
called multiple times during repository setup, and we don't want to
create the object database multiple times. This is somewhat tangled and
hard to follow.
Remove the logic from `repo_set_gitdir()` and instead initialize the
object database outside of it. This leads to some duplication right now,
but that duplication will be removed in a subsequent step where we will
start initializing the object database as part of applying the repo's
format.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
After having discovered the repository format we then apply it to the
repository so that it knows to use the proper repository extensions. The
logic to apply the format is duplicated across three callsites, which
makes it rather painfull to add new extensions.
Introduce a new function `apply_repository_format()` that takes a repo
and applies a given format to it and adapt all callsites to use it.
This function is also the new caller of `verify_repository_format()` so
that we can ensure that we never apply an invalid repository format.
The verification we have in `read_and_verify_repository_format()` is
thus redundant now and dropped.
Rename `read_and_verify_repository_format()` accordingly. While at it,
also rename `check_repository_format()` to clarify that it doesn't only
_check_ the format, but that it also applies it.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The `setup_git_env()` function is a trivial wrapper around
`setup_git_env_internal()` and has a single call site only. Drop the
function.
While at it, drop stale documentation in "environment.h" that points to
this function, even though it hasn't been exposed to callers outside of
"setup.c" since 43ad1047a9 (setup: stop using `the_repository` in
`setup_git_env()`, 2026-03-27) anymore.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In subsequent commits we'll rework how we set up the repository. This is
a somewhat intricate and thus fragile sequence; there's many things that
can go subtly wrong, and there are lots of interesting interactions that
one can discover.
One such discovered edge case was the interaction between git-init(1)
and the "GIT_OBJECT_DIRECTORY" environment variable. When set, the
behaviour is that the object directory should be created at the path
that the variable points to. This behaviour is documented as such in
its man page:
If the object storage directory is specified via the
GIT_OBJECT_DIRECTORY environment variable then the sha1 directories
are created underneath; otherwise, the default $GIT_DIR/objects
directory is used.
Curiously enough though we don't seem to have any tests that exercise
this directly, and thus a subsequent commit inadvertently would have
broken this expectation.
Plug this test gap.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The "git pack-objects --path-walk" traversal has been integrated
with several object filters, including blobless and sparse filters.
* ds/path-walk-filters:
path-walk: support `combine` filter
path-walk: support `object:type` filter
path-walk: support `tree:0` filter
t6601: tag otherwise-unreachable trees
pack-objects: support sparse:oid filter with path-walk
path-walk: add pl_sparse_trees to control tree pruning
path-walk: support blob size limit filter
backfill: die on incompatible filter options
path-walk: support blobless filter
path-walk: always emit directly-requested objects
t/perf: add pack-objects filter and path-walk benchmark
pack-objects: pass --objects with --path-walk
t5620: make test work with path-walk var
"Friday noon" asked in the morning on Sunday was parsed to be one
day before the specified time, which has been corrected.
* ta/approxidate-noon-fix:
approxidate: use deferred mday adjustments for "specials"
approxidate: make "specials" respect fixed day-of-month
t0006: add support for approxidate test date adjustment
approxidate: make "today" wrap to midnight
The "name" argument in git_connect() and related functions has been
converted to a "service" enum to improve type safety and clarify its
purpose.
* jk/connect-service-enum:
transport-helper: fix typo in BUG() message
connect: use "service" enum for "name" argument
"git cat-file --batch" learns an in-line command "mailmap"
that lets the user toggle use of mailmap.
* sa/cat-file-batch-mailmap-switch:
cat-file: add mailmap subcommand to --batch-command
The logic to lazy-load trees from the commit-graph has been made
more robust by falling back to reading the commit object when
the commit-graph is no longer available.
* jk/commit-graph-lazy-load-fallback:
commit: fall back to full read when maybe_tree is NULL
The fsmonitor daemon has been implemented for Linux.
* pt/fsmonitor-linux:
fsmonitor: convert shown khash to strset in do_handle_client
fsmonitor: add tests for Linux
fsmonitor: add timeout to daemon stop command
fsmonitor: close inherited file descriptors and detach in daemon
run-command: add close_fd_above_stderr option
fsmonitor: implement filesystem change listener for Linux
fsmonitor: rename fsm-settings-darwin.c to fsm-settings-unix.c
fsmonitor: rename fsm-ipc-darwin.c to fsm-ipc-unix.c
fsmonitor: use pthread_cond_timedwait for cookie wait
compat/win32: add pthread_cond_timedwait
fsmonitor: fix hashmap memory leak in fsmonitor_run_daemon
fsmonitor: fix khash memory leak in do_handle_client
t9210, t9211: disable GIT_TEST_SPLIT_INDEX for scalar clone tests
The graph output from commands like "git log --graph" can now be
limited to a specified number of lanes, preventing overly wide output
in repositories with many branches.
* ps/graph-lane-limit:
graph: add truncation mark to capped lanes
graph: add --graph-lane-limit option
graph: limit the graph width to a hard-coded max
"git bisect" now uses the selected terms (e.g., old/new) more
consistently in its output.
* jr/bisect-custom-terms-in-output:
rev-parse: use selected alternate terms to look up refs
bisect: print bisect terms in single quotes
bisect: use selected alternate terms in status output
Revision traversal optimization.
* kk/tips-reachable-from-bases-optim:
t6600: add tests for duplicate tips in tips_reachable_from_bases()
commit-reach: use object flags for tips_reachable_from_bases()
These functions were deprecated in a series of commits merged in
52882024 (Merge branch 'ps/commit-list-functions-renamed', 2026-02-13).
The compatibility was for in-flight topics at the time.
Acked-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Replace `free_commit_list` with `commit_list_free`. The former was
deprecated in 9f18d089 (commit: rename `free_commit_list()` to conform
to coding guidelines, 2026-01-15).
This allows us to remove all the deprecated functions in the
next commit:
• `copy_commit_list`
• `reverse_commit_list`
• `free_commit_list`
Acked-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When generating bitmaps, `bitmap_builder_init()` starts with an initial
selection of commits to receive bitmap coverage, and then determines a
set of "maximal" commits based on its input.
Commit 089f751360 (pack-bitmap-write: build fewer intermediate bitmaps,
2020-12-08) has extensive details, but the gist is as follows:
Each selected commit starts with one commit_mask bit in its "commit
mask" bitmap. Then, we walk the first-parent history in topological
order and OR each commit's mask into its (first) parent. Whenever that
OR results in the parent having more bits set, the child is deemed to be
non-maximal, and the frontier is pushed further back along the first
parent history.
That approach works extremely well for ordinary selected commits, whose
first-parent histories often describe real sharing between the bitmaps
we are going to write.
It struggles, however, to efficiently generate pseudo-merge bitmaps.
Unlike ordinary commits for which the above algorithm is designed,
pseudo-merges don't represent any "real" commit in history, just a
grouping of non-bitmapped reference tips. In that sense, their first
parent is just a part of a larger set, and treating them like ordinary
selected commits imposes a significant slow-down when generating bitmaps
with pseudo-merges enabled.
Consider partitioning all non-bitmapped reference tips into eight
individual pseudo-merges via the following configuration:
[bitmapPseudoMerge "all"]
pattern=refs/
threshold=now
stableSize=10000000
maxMerges=8
, the cost of generating a bitmap from scratch rises significantly:
+------------------+-----------------+---------------+---------------------+
| | no pseudo-merge | pseudo-merges | Delta |
| | | (HEAD^) | |
+------------------+-----------------+---------------+---------------------+
| elapsed | 294.1 s | 575.0 s | +280.9 s (+95.5%) |
| cycles | 1,365.5 B | 2,686.9 B | +1,321.4 B (+96.8%) |
| instructions | 1,389.8 B | 2,546.6 B | +1,156.8 B (+83.2%) |
| CPI | 0.983 | 1.055 | +0.073 (+7.4%) |
+------------------+-----------------+---------------+---------------------+
This is a particularly poor trade-off, because the time saved by these
pseudo-merges during, e.g.,
$ git rev-list --count --all --objects --use-bitmap-index
is only:
$ hyperfine -L v true,false -n 'pseudo-merges: {v}' '
GIT_TEST_USE_PSEUDO_MERGES={v} git.compile rev-list --count \
--objects --all --use-bitmap-index
'
Benchmark 1: pseudo-merges: true
Time (mean ± σ): 2.613 s ± 0.012 s [User: 2.308 s, System: 0.305 s]
Range (min … max): 2.594 s … 2.633 s 10 runs
Benchmark 2: pseudo-merges: false
Time (mean ± σ): 52.205 s ± 0.170 s [User: 51.500 s, System: 0.697 s]
Range (min … max): 51.956 s … 52.458 s 10 runs
Summary
pseudo-merges: true ran
19.98 ± 0.11 times faster than pseudo-merges: false
In other words, we pay a nearly ~5 minute penalty to generate
pseudo-merge bitmaps, but only save ~50 seconds during traversal.
The problem stems from injecting pseudo-merges into the bitmap builder
as if they were normal commits. The maximal commit selection algorithm
was simply not designed for that case, and performs predictably poorly.
The only reason we reused the maximal commit selection routine for
pseudo-merges alongside regular non-pseudo-merge commits is because we
represent them both as commit objects (where the pseudo-merge commits
just represent a made-up commit as opposed to one that actually exists
in a repository's object store).
Instead, build the regular selected commit bitmaps first, considering
only non-pseudo-merge commits in `bitmap_builder_init()`. Once those
bitmaps have been stored, build each pseudo-merge bitmap separately and
attach its parent and object bitmaps to the corresponding pseudo-merge
entry before writing the extension.
This keeps the regular bitmap build shaped like the no-pseudo-merge
case. The later pseudo-merge fill can still stop at stored selected
ancestor bitmaps, so it does not have to rewalk each pseudo-merge
closure from scratch.
When an existing bitmap has the same pseudo-merge parent set, reuse and
remap that whole pseudo-merge bitmap before falling back to
fill_bitmap_commit(). This preserves the benefit of stable pseudo-merges
while keeping the on-disk format and reader behavior unchanged.
As a result, the overhead cost for generating pseudo-merges in the above
configuration is much smaller:
+------------------+-----------------+---------------+-------------------+
| | no pseudo-merge | pseudo-merges | Delta |
| | | (HEAD) | |
+------------------+-----------------+---------------+-------------------+
| elapsed | 294.1 s | 328.4 s | +34.3 s (+11.7%) |
| cycles | 1,365.5 B | 1,529.3 B | +163.7 B (+12.0%) |
| instructions | 1,389.8 B | 1,552.8 B | +163.0 B (+11.7%) |
| CPI | 0.983 | 0.985 | +0.002 (+0.2%) |
+------------------+-----------------+---------------+-------------------+
Recall that at the start of this series, generating reachability bitmaps
took 612.5 seconds *without* pseudo-merges. With this commit, it is
still ~46.38% *faster* to generate reachability bitmaps *with*
pseudo-merges than it was to generate bitmaps wihtout them at the
beginning of this series.
The changes to implement this are mostly straightforward. We exclude
pseudo-merge commits from the existing bitmap generation, and walk over
them in a separate pass, by either reusing an existing on-disk
pseudo-merge, or passing the pseudo-merge commit itself back to the
existing routine in `fill_bitmap_commit()`.
(Note that the routine to build pseudo-merge bitmaps is the same both
before and after this change, the difference is only that we do not let
psuedo-merges participate in determining the set of maximal commits.)
The only wrinkle is that `fill_bitmap_commit()` must be taught to not
expect that all tree objects have been parsed, which is the case for any
portion of history reachable by one or more pseudo-merge(s), but not by
any non-pseudo-merge commit selected for bitmapping.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
write_pseudo_merges() currently builds an array of temporary bitmaps for
the parent set of each pseudo-merge, then serializes those bitmaps later
while writing the extension.
Move those parent bitmaps onto the corresponding bitmapped_commit
entries instead. This keeps the on-disk output unchanged, but gives the
parent bitmap the same lifetime and access pattern that later changes
will use when pseudo-merge object bitmaps are built before the write
step.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Reachability bitmaps may be stored as XORs against nearby bitmaps, up to
10 away. However, when callers provide selected commits in an arbitrary
order, the writer may miss good ancestor/descendant pairs and produce
much larger bitmap files without changing query coverage.
Sort the selected bitmaps in date order (from oldest to newest) before
computing XOR offsets, leaving pseudo-merge bitmaps alone (which we will
deal with separately in following commits).
On our same testing repository from previous commits, this change shrunk
our selection of 1,261 bitmaps from ~635.46 MiB to 176.4 MiB for a
~72.24% reduction in the on-disk size of our *.bitmap file. The time to
generate the smaller bitmap file decreased by ~3.69 seconds, though this
is likely mostly noise.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The previous commits removed some redundant work from bitmap generation
by avoiding unnecessary tree recursion and by reusing selected bitmaps
that have already been computed.
Even with those changes in place, there is still an extremely hot path
from `fill_bitmap_commit()` and `fill_bitmap_tree()` to translate object
IDs into their corresponding bit positions in order to generate their
bitmaps.
In a small repository, this overhead is not significant. However, in a
very large repository (e.g., the one that we have been using as a
benchmark over the past several commits with ~57M total objects), the
overhead of locating object bit positions (often repeatedly) adds up
significantly.
Combat this by adding a small, direct-mapped cache to the bitmap writer
which maps object IDs to their corresponding bit positions. Size the
cache according to the number of objects being written, with fixed lower
and upper bounds so small repositories do not pay for a large table and
large repositories can avoid most repeated packlist and MIDX lookups.
On my machine with (a somewhat outdated) GCC 15.2.0, each entry in the
cache is 40 bytes wide:
$ pahole -C bitmap_pos_cache_entry pack-bitmap-write.o
struct bitmap_pos_cache_entry {
struct object_id oid; /* 0 36 */
uint32_t pos; /* 36 4 */
/* size: 40, cachelines: 1, members: 2 */
/* last cacheline: 40 bytes */
};
, and we will allocate up to 2^21 entries for a maximum total of 80 MiB
of cache overhead.
In our example repository from above and in earlier commits, this
results in a ~9.4% reduction in runtime relative to the previous commit:
+------------------+-------------+-------------+---------------------+
| | HEAD^ | HEAD | Delta |
+------------------+-------------+-------------+---------------------+
| elapsed | 324.8 s | 294.1 s | -30.7 s (-9.4%) |
| cycles | 1,508.6 B | 1,365.5 B | -143.0 B (-9.5%) |
| instructions | 1,436.6 B | 1,389.8 B | -46.9 B (-3.3%) |
| CPI | 1.050 | 0.983 | -0.068 (-6.4%) |
+------------------+-------------+-------------+---------------------+
When generating bitmaps on this repository (to produce the above
timings), the cache grew to its maximum size of 80 MiB, and resulted in
1.024B cache hits and 59.957M cache misses.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Both sides of `find_object_pos()` report success in the same way by
setting the optional `found` out-parameter and return the resolved
bitmap position.
Prepare for adding more bookkeeping around object-position lookups by
storing the result in a local `pos` variable and sharing the success
return path between the packlist and MIDX cases.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When `fill_bitmap_commit()` reaches an ancestor that was selected for
its own bitmap and processed earlier, its object closure is already
stored in `writer->bitmaps` as an EWAH bitmap. As a result, walking
through that commit's tree and parents again is redundant.
Teach `fill_bitmap_commit()` to notice that case. For non-root commits in
the walk, look for a stored selected bitmap and OR it into the bitmap
being built. If one exists, skip the commit, its tree, and its parents.
Building bitmaps from scratch on the same test repository from the
previous commits yields a significant speed-up:
+------------------+-------------+-------------+---------------------+
| | HEAD^ | HEAD | Delta |
+------------------+-------------+-------------+---------------------+
| elapsed | 562.8 s | 324.8 s | -237.9 s (-42.3%) |
| cycles | 2,621.3 B | 1,508.6 B | -1,112.7 B (-42.4%) |
| instructions | 2,348.9 B | 1,436.6 B | -912.3 B (-38.8%) |
| CPI | 1.116 | 1.050 | -0.066 (-5.9%) |
+------------------+-------------+-------------+---------------------+
In our testing repository, there are 1,261 commits selected for bitmap
coverage, and 1,382 maximal commits induced as a result of that. Of the
1,382 calls made to `fill_bitmap_commit()` (one per maximal commit), 131
of them can be short-circuited at some point during their traversal as a
consequence of this change.
In large repositories where the cost of filling the bitmap for any
individual commit is large, being able to short-circuit even ~9.5% of
the calls to `fill_bitmap_commit()` results in a significant savings.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
