Add progress output to be shown when we're writing out the
commit-graph, this adds to the output already added in 7b0f229222
("commit-graph write: add progress output", 2018-09-17).
As noted in that commit most of the progress output isn't displayed on
small repositories, but before this change we'd noticeably hang for
2-3 seconds at the end on medium sized repositories such as linux.git.
Now we'll instead show output like this, and reduce the
human-observable times at which we're not producing progress output:
$ ~/g/git/git --exec-path=$HOME/g/git -C ~/g/2015-04-03-1M-git commit-graph write
Finding commits for commit graph: 13064614, done.
Expanding reachable commits in commit graph: 1000447, done.
Computing commit graph generation numbers: 100% (1000447/1000447), done.
Writing out commit graph: 100% (3001341/3001341), done.
This "Writing out" number is 3x or 4x the number of commits, depending
on the graph we're processing. A later change will make this explicit
to the user.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The optional 'Extra Edge List' chunk of the commit graph file stores
parent information for commits with more than two parents. Since the
chunk is optional, write_commit_graph() looks through all commits to
find those with more than two parents, and then writes the commit
graph file header accordingly, i.e. if there are no such commits, then
there won't be a 'Extra Edge List' chunk written, only the three
mandatory chunks.
However, when it later comes to writing actual chunk data,
write_commit_graph() unconditionally invokes
write_graph_chunk_extra_edges(), even when it was decided earlier that
that chunk won't be written. Strictly speaking there is no bug here,
because write_graph_chunk_extra_edges() won't write anything if it
doesn't find any commits with more than two parents, but then it
unnecessarily and in vain looks through all commits once again in
search for such commits.
Don't call write_graph_chunk_extra_edges() when that chunk won't be
written to spare an unnecessary iteration over all commits.
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The optional 'Large Edge List' chunk of the commit graph file stores
parent information for commits with more than two parents, and the
names of most of the macros, variables, struct fields, and functions
related to this chunk contain the term "large edges", e.g.
write_graph_chunk_large_edges(). However, it's not a really great
term, as the edges to the second and subsequent parents stored in this
chunk are not any larger than the edges to the first and second
parents stored in the "main" 'Commit Data' chunk. It's the number of
edges, IOW number of parents, that is larger compared to non-merge and
"regular" two-parent merge commits. And indeed, two functions in
'commit-graph.c' have a local variable called 'num_extra_edges' that
refer to the same thing, and this "extra edges" term is much better at
describing these edges.
So let's rename all these references to "large edges" in macro,
variable, function, etc. names to "extra edges". There is a
GRAPH_OCTOPUS_EDGES_NEEDED macro as well; for the sake of consistency
rename it to GRAPH_EXTRA_EDGES_NEEDED.
We can do so safely without causing any incompatibility issues,
because the term "large edges" doesn't come up in the file format
itself in any form (the chunk's magic is {'E', 'D', 'G', 'E'}, there
is no 'L' in there), but only in the specification text. The string
"large edges", however, does come up in the output of 'git
commit-graph read' and in tests looking at its input, but that command
is explicitly documented as debugging aid, so we can change its output
and the affected tests safely.
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Slightly optimize the "commit-graph write" step by using
FOR_EACH_OBJECT_PACK_ORDER with for_each_object_in_pack(). See commit
[1] and [2] for the facility and a similar optimization for "cat-file".
On Linux it is around 5% slower to run:
echo 1 >/proc/sys/vm/drop_caches &&
cat .git/objects/pack/* >/dev/null &&
git cat-file --batch-all-objects --batch-check --unordered
Than the same thing with the "cat" omitted. This is as expected, since
we're iterating in pack order and the "cat" is extra work.
Before this change the opposite was true of "commit-graph write". We
were 6% faster if we first ran "cat" to efficiently populate the FS
cache for our sole big pack on linux.git, than if we had populated it
via for_each_object_in_pack(). Now we're 3% faster without the "cat"
instead.
My tests were done on an unloaded Linux 3.10 system with 10 runs for
each. Derrick Stolee did his own tests on Windows[3] showing a 2%
improvement with a high degree of accuracy.
1. 736eb88fdc ("for_each_packed_object: support iterating in
pack-order", 2018-08-10)
2. 0750bb5b51 ("cat-file: support "unordered" output for
--batch-all-objects", 2018-08-10)
3. https://public-inbox.org/git/f71fa868-25e8-a9c9-46a6-611b987f1a8f@gmail.com/
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Amend the progress output added in 7b0f229222 ("commit-graph write:
add progress output", 2018-09-17) so that the total numbers it reports
aren't higher than the total number of commits anymore. See [1] for a
bug report pointing that out.
When I added this I wasn't intending to provide an accurate count, but
just have some progress output to show the user the command wasn't
hanging[2]. But since we are showing numbers, let's make them
accurate. The progress descriptions were suggested by Derrick Stolee
in [3].
As noted in [2] we are unlikely to show anything except the "Expanding
reachable..." message even on fairly large repositories such as
linux.git. On a test repository I have with north of 7 million commits
all of these are displayed. Two of them don't show up for long, but as
noted in [5] future-proofing this for if the loops become more
expensive in the future makes sense.
1. https://public-inbox.org/git/20181010203738.GE23446@szeder.dev/
2. https://public-inbox.org/git/87pnwhea8y.fsf@evledraar.gmail.com/
3. https://public-inbox.org/git/f7a0cbee-863c-61d3-4959-5cec8b43c705@gmail.com/
4. https://public-inbox.org/git/20181015160545.GG19800@szeder.dev/
5. https://public-inbox.org/git/87murle8da.fsf@evledraar.gmail.com/
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Helped-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Our handling of alternate object directories is needlessly different
from the main object directory. As a result, many places in the code
basically look like this:
do_something(r->objects->objdir);
for (odb = r->objects->alt_odb_list; odb; odb = odb->next)
do_something(odb->path);
That gets annoying when do_something() is non-trivial, and we've
resorted to gross hacks like creating fake alternates (see
find_short_object_filename()).
Instead, let's give each raw_object_store a unified list of
object_directory structs. The first will be the main store, and
everything after is an alternate. Very few callers even care about the
distinction, and can just loop over the whole list (and those who care
can just treat the first element differently).
A few observations:
- we don't need r->objects->objectdir anymore, and can just
mechanically convert that to r->objects->odb->path
- object_directory's path field needs to become a real pointer rather
than a FLEX_ARRAY, in order to fill it with expand_base_dir()
- we'll call prepare_alt_odb() earlier in many functions (i.e.,
outside of the loop). This may result in us calling it even when our
function would be satisfied looking only at the main odb.
But this doesn't matter in practice. It's not a very expensive
operation in the first place, and in the majority of cases it will
be a noop. We call it already (and cache its results) in
prepare_packed_git(), and we'll generally check packs before loose
objects. So essentially every program is going to call it
immediately once per program.
Arguably we should just prepare_alt_odb() immediately upon setting
up the repository's object directory, which would save us sprinkling
calls throughout the code base (and forgetting to do so has been a
source of subtle bugs in the past). But I've stopped short of that
here, since there are already a lot of other moving parts in this
patch.
- Most call sites just get shorter. The check_and_freshen() functions
are an exception, because they have entry points to handle local and
nonlocal directories separately.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In preparation for unifying the handling of alt odb's and the normal
repo object directory, let's use a more neutral name. This patch is
purely mechanical, swapping the type name, and converting any variables
named "alt" to "odb". There should be no functional change, but it will
reduce the noise in subsequent diffs.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The recently introduced commit-graph auxiliary data is incompatible
with mechanisms such as replace & grafts that "breaks" immutable
nature of the object reference relationship. Disable optimizations
based on its use (and updating existing commit-graph) when these
incompatible features are in use in the repository.
* ds/commit-graph-with-grafts:
commit-graph: close_commit_graph before shallow walk
commit-graph: not compatible with uninitialized repo
commit-graph: not compatible with grafts
commit-graph: not compatible with replace objects
test-repository: properly init repo
commit-graph: update design document
refs.c: upgrade for_each_replace_ref to be a each_repo_ref_fn callback
refs.c: migrate internal ref iteration to pass thru repository argument
Generation of (experimental) commit-graph files have so far been
fairly silent, even though it takes noticeable amount of time in a
meaningfully large repository. The users will now see progress
output.
* ab/commit-graph-progress:
gc: fix regression in 7b0f229222 impacting --quiet
commit-graph verify: add progress output
commit-graph write: add progress output
While writing a commit-graph file, we store the full list of
commits in a flat list. We use this list for sorting and ensuring
we are closed under reachability.
The initial allocation assumed that (at most) one in four objects
is a commit. This is a dramatic over-count for many repos,
especially large ones. Since we grow the repo dynamically, reduce
this count by a factor of eight. We still set it to a minimum of
1024 before allocating.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The write_commit_graph() method in commit-graph.c leaks some lits
and strings during execution. In addition, a list of strings is
leaked in write_commit_graph_reachable(). Clean these up so our
memory checking is cleaner.
Further, if we use a list of pack-files to find the commits, we
can leak the packed_git structs after scanning them for commits.
Running the following commands demonstrates the leak before and
the fix after:
* valgrind --leak-check=full ./git commit-graph write --reachable
* valgrind --leak-check=full ./git commit-graph write --stdin-packs
Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
spatch transformation to replace boolean uses of !hashcmp() to
newly introduced oideq() is added, and applied, to regain
performance lost due to support of multiple hash algorithms.
* jk/cocci:
show_dirstat: simplify same-content check
read-cache: use oideq() in ce_compare functions
convert hashmap comparison functions to oideq()
convert "hashcmp() != 0" to "!hasheq()"
convert "oidcmp() != 0" to "!oideq()"
convert "hashcmp() == 0" to hasheq()
convert "oidcmp() == 0" to oideq()
introduce hasheq() and oideq()
coccinelle: use <...> for function exclusion
The code for computing history reachability has been shuffled,
obtained a bunch of new tests to cover them, and then being
improved.
* ds/reachable:
commit-reach: correct accidental #include of C file
commit-reach: use can_all_from_reach
commit-reach: make can_all_from_reach... linear
commit-reach: replace ref_newer logic
test-reach: test commit_contains
test-reach: test can_all_from_reach_with_flags
test-reach: test reduce_heads
test-reach: test get_merge_bases_many
test-reach: test is_descendant_of
test-reach: test in_merge_bases
test-reach: create new test tool for ref_newer
commit-reach: move can_all_from_reach_with_flags
upload-pack: generalize commit date cutoff
upload-pack: refactor ok_to_give_up()
upload-pack: make reachable() more generic
commit-reach: move commit_contains from ref-filter
commit-reach: move ref_newer from remote.c
commit.h: remove method declarations
commit-reach: move walk methods from commit.c
For the reasons explained in the "commit-graph write: add progress
output" commit leading up to this one, emit progress on "commit-graph
verify". Since e0fd51e1d7 ("fsck: verify commit-graph", 2018-06-27)
"git fsck" has called this command if core.commitGraph=true, but
there's been no progress output to indicate that anything was
different. Now there is (on my tiny dotfiles.git repository):
$ git -c core.commitGraph=true -C ~/ fsck
Checking object directories: 100% (256/256), done.
Checking objects: 100% (2821/2821), done.
dangling blob 5b8bbdb9b788ed90459f505b0934619c17cc605b
Verifying commits in commit graph: 100% (867/867), done.
And on a larger repository, such as the 2015-04-03-1M-git.git test
repository:
$ time git -c core.commitGraph=true -C ~/g/2015-04-03-1M-git/ commit-graph verify
Verifying commits in commit graph: 100% (1000447/1000447), done.
real 0m7.813s
[...]
Since the "commit-graph verify" subcommand is never called from "git
gc", we don't have to worry about passing some some "report_progress"
progress variable around for this codepath.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Before this change the "commit-graph write" command didn't report any
progress. On my machine this command takes more than 10 seconds to
write the graph for linux.git, and around 1m30s on the
2015-04-03-1M-git.git[1] test repository (a test case for a large
monorepository).
Furthermore, since the gc.writeCommitGraph setting was added in
d5d5d7b641 ("gc: automatically write commit-graph files", 2018-06-27),
there was no indication at all from a "git gc" run that anything was
different. This why one of the progress bars being added here uses
start_progress() instead of start_delayed_progress(), so that it's
guaranteed to be seen. E.g. on my tiny 867 commit dotfiles.git
repository:
$ git -c gc.writeCommitGraph=true gc
Enumerating objects: 2821, done.
[...]
Computing commit graph generation numbers: 100% (867/867), done.
On larger repositories, such as linux.git the delayed progress bar(s)
will kick in, and we'll show what's going on instead of, as was
previously happening, printing nothing while we write the graph:
$ git -c gc.writeCommitGraph=true gc
[...]
Annotating commits in commit graph: 1565573, done.
Computing commit graph generation numbers: 100% (782484/782484), done.
Note that here we don't show "Finding commits for commit graph", this
is because under "git gc" we seed the search with the commit
references in the repository, and that set is too small to show any
progress, but would e.g. on a smaller repo such as git.git with
--stdin-commits:
$ git rev-list --all | git -c gc.writeCommitGraph=true write --stdin-commits
Finding commits for commit graph: 100% (162576/162576), done.
Computing commit graph generation numbers: 100% (162576/162576), done.
With --stdin-packs we don't show any estimation of how much is left to
do. This is because we might be processing more than one pack. We
could be less lazy here and show progress, either by detecting that
we're only processing one pack, or by first looping over the packs to
discover how many commits they have. I don't see the point in doing
that work. So instead we get (on 2015-04-03-1M-git.git):
$ echo pack-<HASH>.idx | git -c gc.writeCommitGraph=true --exec-path=$PWD commit-graph write --stdin-packs
Finding commits for commit graph: 13064614, done.
Annotating commits in commit graph: 3001341, done.
Computing commit graph generation numbers: 100% (1000447/1000447), done.
No GC mode uses --stdin-packs. It's what they use at Microsoft to
manually compute the generation numbers for their collection of large
packs which are never coalesced.
The reason we need a "report_progress" variable passed down from "git
gc" is so that we don't report this output when we're running in the
process "git gc --auto" detaches from the terminal.
Since we write the commit graph from the "git gc" process itself (as
opposed to what we do with say the "git repack" phase), we'd end up
writing the output to .git/gc.log and reporting it to the user next
time as part of the "The last gc run reported the following[...]"
error, see 329e6e8794 ("gc: save log from daemonized gc --auto and
print it next time", 2015-09-19).
So we must keep track of whether or not we're running in that
demonized mode, and if so print no progress.
See [2] and subsequent replies for a discussion of an approach not
taken in compute_generation_numbers(). I.e. we're saying "Computing
commit graph generation numbers", even though on an established
history we're mostly skipping over all the work we did in the
past. This is similar to the white lie we tell in the "Writing
objects" phase (not all are objects being written).
Always showing progress is considered more important than
accuracy. I.e. on a repository like 2015-04-03-1M-git.git we'd hang
for 6 seconds with no output on the second "git gc" if no changes were
made to any objects in the interim if we'd take the approach in [2].
1. https://github.com/avar/2015-04-03-1M-git
2. <c6960252-c095-fb2b-e0bc-b1e6bb261614@gmail.com>
(https://public-inbox.org/git/c6960252-c095-fb2b-e0bc-b1e6bb261614@gmail.com/)
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This rounds out the previous three patches, covering the
inequality logic for the "hash" variant of the functions.
As with the previous three, the accompanying code changes
are the mechanical result of applying the coccinelle patch;
see those patches for more discussion.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This is the flip side of the previous two patches: checking
for a non-zero oidcmp() can be more strictly expressed as
inequality. Like those patches, we write "!= 0" in the
coccinelle transformation, which covers by isomorphism the
more common:
if (oidcmp(E1, E2))
As with the previous two patches, this patch can be achieved
almost entirely by running "make coccicheck"; the only
differences are manual line-wrap fixes to match the original
code.
There is one thing to note for anybody replicating this,
though: coccinelle 1.0.4 seems to miss the case in
builtin/tag.c, even though it's basically the same as all
the others. Running with 1.0.7 does catch this, so
presumably it's just a coccinelle bug that was fixed in the
interim.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Using the more restrictive oideq() should, in the long run,
give the compiler more opportunities to optimize these
callsites. For now, this conversion should be a complete
noop with respect to the generated code.
The result is also perhaps a little more readable, as it
avoids the "zero is equal" idiom. Since it's so prevalent in
C, I think seasoned programmers tend not to even notice it
anymore, but it can sometimes make for awkward double
negations (e.g., we can drop a few !!oidcmp() instances
here).
This patch was generated almost entirely by the included
coccinelle patch. This mechanical conversion should be
completely safe, because we check explicitly for cases where
oidcmp() is compared to 0, which is what oideq() is doing
under the hood. Note that we don't have to catch "!oidcmp()"
separately; coccinelle's standard isomorphisms make sure the
two are treated equivalently.
I say "almost" because I did hand-edit the coccinelle output
to fix up a few style violations (it mostly keeps the
original formatting, but sometimes unwraps long lines).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The commit-graph feature is tested in isolation by
t5318-commit-graph.sh and t6600-test-reach.sh, but there are many
more interesting scenarios involving commit walks. Many of these
scenarios are covered by the existing test suite, but we need to
maintain coverage when the optional commit-graph structure is not
present.
To allow running the full test suite with the commit-graph present,
add a new test environment variable, GIT_TEST_COMMIT_GRAPH. Similar
to GIT_TEST_SPLIT_INDEX, this variable makes every Git command try
to load the commit-graph when parsing commits, and writes the
commit-graph file after every 'git commit' command.
There are a few tests that rely on commits not existing in
pack-files to trigger important events, so manually set
GIT_TEST_COMMIT_GRAPH to false for the necessary commands.
There is one test in t6024-recursive-merge.sh that relies on the
merge-base algorithm picking one of two ambiguous merge-bases, and
the commit-graph feature changes which merge-base is picked.
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Call close_commit_graph() when about to start a rev-list walk that
includes shallow commits. This is necessary in code paths that "fake"
shallow commits for the sake of fetch. Specifically, test 351 in
t5500-fetch-pack.sh runs
git fetch --shallow-exclude one origin
with a file-based transfer. When the "remote" has a commit-graph, we do
not prevent the commit-graph from being loaded, but then the commits are
intended to be dynamically transferred into shallow commits during
get_shallow_commits_by_rev_list(). By closing the commit-graph before
this call, we prevent this interaction.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Augment commit_graph_compatible(r) to return false when the given
repository r has commit grafts or is a shallow clone. Test that in these
situations we ignore existing commit-graph files and we do not write new
commit-graph files.
Helped-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Create new method commit_graph_compatible(r) to check if a given
repository r is compatible with the commit-graph feature. Fill the
method with a check to see if replace-objects exist. Test this
interaction succeeds, including ignoring an existing commit-graph and
failing to write a new commit-graph. However, we do ensure that
we write a new commit-graph by setting read_replace_refs to 0, thereby
ignoring the replace refs.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The API to iterate over all objects learned to optionally list
objects in the order they appear in packfiles, which helps locality
of access if the caller accesses these objects while as objects are
enumerated.
* jk/for-each-object-iteration:
for_each_*_object: move declarations to object-store.h
cat-file: use a single strbuf for all output
cat-file: split batch "buf" into two variables
cat-file: use oidset check-and-insert
cat-file: support "unordered" output for --batch-all-objects
cat-file: rename batch_{loose,packed}_object callbacks
t1006: test cat-file --batch-all-objects with duplicates
for_each_packed_object: support iterating in pack-order
for_each_*_object: give more comprehensive docstrings
for_each_*_object: take flag arguments as enum
for_each_*_object: store flag definitions in a single location
Many more strings are prepared for l10n.
* nd/i18n: (23 commits)
transport-helper.c: mark more strings for translation
transport.c: mark more strings for translation
sha1-file.c: mark more strings for translation
sequencer.c: mark more strings for translation
replace-object.c: mark more strings for translation
refspec.c: mark more strings for translation
refs.c: mark more strings for translation
pkt-line.c: mark more strings for translation
object.c: mark more strings for translation
exec-cmd.c: mark more strings for translation
environment.c: mark more strings for translation
dir.c: mark more strings for translation
convert.c: mark more strings for translation
connect.c: mark more strings for translation
config.c: mark more strings for translation
commit-graph.c: mark more strings for translation
builtin/replace.c: mark more strings for translation
builtin/pack-objects.c: mark more strings for translation
builtin/grep.c: mark strings for translation
builtin/config.c: mark more strings for translation
...
We currently iterate over objects within a pack in .idx
order, which uses the object hashes. That means that it
is effectively random with respect to the location of the
object within the pack. If you're going to access the actual
object data, there are two reasons to move linearly through
the pack itself:
1. It improves the locality of access in the packfile. In
the cold-cache case, this may mean fewer disk seeks, or
better usage of disk cache.
2. We store related deltas together in the packfile. Which
means that the delta base cache can operate much more
efficiently if we visit all of those related deltas in
sequence, as the earlier items are likely to still be
in the cache. Whereas if we visit the objects in
random order, our cache entries are much more likely to
have been evicted by unrelated deltas in the meantime.
So in general, if you're going to access the object contents
pack order is generally going to end up more efficient.
But if you're simply generating a list of object names, or
if you're going to end up sorting the result anyway, you're
better off just using the .idx order, as finding the pack
order means generating the in-memory pack-revindex.
According to the numbers in 8b8dfd5132 (pack-revindex:
radix-sort the revindex, 2013-07-11), that takes about 200ms
for linux.git, and 20ms for git.git (those numbers are a few
years old but are still a good ballpark).
That makes it a good optimization for some cases (we can
save tens of seconds in git.git by having good locality of
delta access, for a 20ms cost), but a bad one for others
(e.g., right now "cat-file --batch-all-objects
--batch-check="%(objectname)" is 170ms in git.git, so adding
20ms to that is noticeable).
Hence this patch makes it an optional flag. You can't
actually do any interesting timings yet, as it's not plumbed
through to any user-facing tools like cat-file. That will
come in a later patch.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The is_descendant_of method previously used in_merge_bases() to check if
the commit can reach any of the commits in the provided list. This had
two performance problems:
1. The performance is quadratic in worst-case.
2. A single in_merge_bases() call requires walking beyond the target
commit in order to find the full set of boundary commits that may be
merge-bases.
The can_all_from_reach method avoids this quadratic behavior and can
limit the search beyond the target commits using generation numbers. It
requires a small prototype adjustment to stop using commit-date as a
cutoff, as that optimization is no longer appropriate here.
Since in_merge_bases() uses paint_down_to_common(), is_descendant_of()
naturally found cutoffs to avoid walking the entire commit graph. Since
we want to always return the correct result, we cannot use the
min_commit_date cutoff in can_all_from_reach. We then rely on generation
numbers to provide the cutoff.
Since not all repos will have a commit-graph file, nor will we always
have generation numbers computed for a commit-graph file, create a new
method, generation_numbers_enabled(), that checks for a commit-graph
file and sees if the first commit in the file has a non-zero generation
number. In the case that we do not have generation numbers, use the old
logic for is_descendant_of().
Performance was meausured on a copy of the Linux repository using the
'test-tool reach is_descendant_of' command using this input:
A:v4.9
X:v4.10
X:v4.11
X:v4.12
X:v4.13
X:v4.14
X:v4.15
X:v4.16
X:v4.17
X.v3.0
Note that this input is tailored to demonstrate the quadratic nature of
the previous method, as it will compute merge-bases for v4.9 versus all
of the later versions before checking against v4.1.
Before: 0.26 s
After: 0.21 s
Since we previously used the is_descendant_of method in the ref_newer
method, we also measured performance there using
'test-tool reach ref_newer' with this input:
A:v4.9
B:v3.19
Before: 0.10 s
After: 0.08 s
By adding a new commit with parent v3.19, we test the non-reachable case
of ref_newer:
Before: 0.09 s
After: 0.08 s
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a struct repository argument to the functions in commit-graph.h that
read the commit graph. (This commit does not affect functions that write
commit graphs.)
Because the commit graph functions can now read the commit graph of any
repository, the global variable core_commit_graph has been removed.
Instead, the config option core.commitGraph is now read on the first
time in a repository that a commit is attempted to be parsed using its
commit graph.
This commit includes a test that exercises the functionality on an
arbitrary repository that is not the_repository.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Instead of storing commit graphs in static variables, store them in
struct object_store. There are no changes to the signatures of existing
functions - they all still only support the_repository, and support for
other instances of struct repository will be added in a subsequent
commit.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Two functions in the code (1) check if the repository is configured for
commit graphs, (2) call prepare_commit_graph(), and (3) check if the
graph exists. Move (1) and (3) into prepare_commit_graph(), reducing
duplication of code.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a repository argument to allow callers of lookup_commit to be more
specific about which repository to handle. This is a small mechanical
change; it doesn't change the implementation to handle repositories
other than the_repository yet.
As with the previous commits, use a macro to catch callers passing a
repository other than the_repository at compile time.
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a repository argument to allow callers of
lookup_commit_reference_gently to be more specific about which
repository to handle. This is a small mechanical change; it doesn't
change the implementation to handle repositories other than
the_repository yet.
As with the previous commits, use a macro to catch callers passing a
repository other than the_repository at compile time.
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a repository argument to allow the callers of lookup_tree
to be more specific about which repository to act on. This is a small
mechanical change; it doesn't change the implementation to handle
repositories other than the_repository yet.
As with the previous commits, use a macro to catch callers passing a
repository other than the_repository at compile time.
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When writing commit-graph files, it can be convenient to ask for all
reachable commits (starting at the ref set) in the resulting file. This
is particularly helpful when writing to stdin is complicated, such as a
future integration with 'git gc'.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The commit-graph file ends with a SHA1 hash of the previous contents. If
a commit-graph file has errors but the checksum hash is correct, then we
know that the problem is a bug in Git and not simply file corruption
after-the-fact.
Compute the checksum right away so it is the first error that appears,
and make the message translatable since this error can be "corrected" by
a user by simply deleting the file and recomputing. The rest of the
errors are useful only to developers.
Be sure to continue checking the rest of the file data if the checksum
is wrong. This is important for our tests, as we break the checksum as
we modify bytes of the commit-graph file.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
While iterating through the commit parents, perform the generation
number calculation and compare against the value stored in the
commit-graph.
The tests demonstrate that having a different set of parents affects
the generation number calculation, and this value propagates to
descendants. Hence, we drop the single-line condition on the output.
Since Git will ship with the commit-graph feature without generation
numbers, we need to accept commit-graphs with all generation numbers
equal to zero. In this case, ignore the generation number calculation.
However, verify that we should never have a mix of zero and non-zero
generation numbers. Create a test that sets one commit to generation
zero and all following commits report a failure as they have non-zero
generation in a file that contains generation number zero.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The commit-graph file stores parents in a two-column portion of the
commit data chunk. If there is only one parent, then the second column
stores 0xFFFFFFFF to indicate no second parent.
The 'verify' subcommand checks the parent list for the commit loaded
from the commit-graph and the one parsed from the object database. Test
these checks for corrupt parents, too many parents, and wrong parents.
Add a boundary check to insert_parent_or_die() for when the parent
position value is out of range.
The octopus merge will be tested in a later commit.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The 'verify' subcommand must compare the commit content parsed from the
commit-graph against the content in the object database. Use
lookup_commit() and parse_commit_in_graph_one() to parse the commits
from the graph and compare against a commit that is loaded separately
and parsed directly from the object database.
Add checks for the root tree OID.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In the 'verify' subcommand, load commits directly from the object
database to ensure they exist. Parse by skipping the commit-graph.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In the commit-graph file, the OID fanout chunk provides an index into
the OID lookup. The 'verify' subcommand should find incorrect values
in the fanout.
Similarly, the 'verify' subcommand should find out-of-order values in
the OID lookup.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The commit-graph file requires the following three chunks:
* OID Fanout
* OID Lookup
* Commit Data
If any of these are missing, then the 'verify' subcommand should
report a failure. This includes the chunk IDs malformed or the
chunk count is truncated.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If the commit-graph file becomes corrupt, we need a way to verify
that its contents match the object database. In the manner of
'git fsck' we will implement a 'git commit-graph verify' subcommand
to report all issues with the file.
Add the 'verify' subcommand to the 'commit-graph' builtin and its
documentation. The subcommand is currently a no-op except for
loading the commit-graph into memory, which may trigger run-time
errors that would be caught by normal use. Add a simple test that
ensures the command returns a zero error code.
If no commit-graph file exists, this is an acceptable state. Do
not report any errors.
Helped-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
