We already store an object_id internally, and now our sole caller also
has one. Let's stop passing around the internal hash array, which adds a
bit of type safety.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When we're considering reusing an on-disk delta, we get the oid of the
base as a pointer to unsigned char bytes of the hash, either into the
packfile itself (for REF_DELTA) or into the pack idx (using the revindex
to convert the offset into an index entry).
Instead, we'd prefer to use a more type-safe object_id as much as
possible. We can get the pack idx using nth_packed_object_id() instead.
For the packfile bytes, we can copy them out using oidread().
This doesn't even incur an extra copy overall, since the next thing we'd
always do with that pointer is pass it to can_reuse_delta(), which needs
an object_id anyway (and called oidread() itself). So this patch also
converts that function to take the object_id directly.
Note that we did previously use NULL as a sentinel value when the object
isn't a delta. We could probably get away with using the null oid for
this, but instead we'll use an explicit boolean flag, which should make
things more obvious for people reading the code later.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Our nth_packed_object_sha1() function returns NULL for error. So when we
wrapped it with nth_packed_object_oid(), we kept the same semantics. But
it's a bit funny, because the caller actually passes in an out
parameter, and the pointer we return is just that same struct they
passed to us (or NULL).
It's not too terrible, but it does make the interface a little
non-idiomatic. Let's switch to our usual "0 for success, negative for
error" return value. Most callers either don't check it, or are
trivially converted. The one that requires the biggest change is
actually improved, as we can ditch an extra aliased pointer variable.
Since we are changing the interface in a subtle way that the compiler
wouldn't catch, let's also change the name to catch any topics in
flight. We can drop the 'o' and make it nth_packed_object_id(). That's
slightly shorter, but also less redundant since the 'o' stands for
"object" already.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Some codepaths were given a repository instance as a parameter to
work in the repository, but passed the_repository instance to its
callees, which has been cleaned up (somewhat).
* mt/use-passed-repo-more-in-funcs:
sha1-file: allow check_object_signature() to handle any repo
sha1-file: pass git_hash_algo to hash_object_file()
sha1-file: pass git_hash_algo to write_object_file_prepare()
streaming: allow open_istream() to handle any repo
pack-check: use given repo's hash_algo at verify_packfile()
cache-tree: use given repo's hash_algo at verify_one()
diff: make diff_populate_filespec() honor its repo argument
Some callers of open_istream() at archive-tar.c and archive-zip.c are
capable of working on arbitrary repositories but the repo struct is not
passed down to open_istream(), which uses the_repository internally. For
now, that's not a problem since the said callers are only being called
with the_repository. But to be consistent and avoid future problems,
let's allow open_istream() to receive a struct repository and use that
instead of the_repository. This parameter addition will also be used in
a future patch to make sha1-file.c:check_object_signature() be able to
work on arbitrary repos.
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Additional checks are added in have_duplicate_entry() and
obj_is_packed() to avoid duplicate objects in the reuse
bitmap. It was probably buggy to not have such a check
before.
Git as a client would never both asks for a tag by sha1 and
specify "include-tag", but libgit2 will, so a libgit2 client
cloning from a Git server would trigger the bug.
If a client both asks for a tag by sha1 and specifies
"include-tag", we may end up including the tag in the reuse
bitmap (due to the first thing), and then later adding it to
the packlist (due to the second). This results in duplicate
objects in the pack, which git chokes on. We should notice
that we are already including it when doing the include-tag
portion, and avoid adding it to the packlist.
The simplest place to fix this is right in add_ref_tag(),
where we could avoid peeling the tag at all if we know that
we are already including it. However, this pushes the check
instead into have_duplicate_entry(). This fixes not only
this case, but also means that we cannot have any similar
problems lurking in other code.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The old code to reuse deltas from an existing packfile
just tried to dump a whole segment of the pack verbatim.
That's faster than the traditional way of actually adding
objects to the packing list, but it didn't kick in very
often. This new code is really going for a middle ground:
do _some_ per-object work, but way less than we'd
traditionally do.
The general strategy of the new code is to make a bitmap
of objects from the packfile we'll include, and then
iterate over it, writing out each object exactly as it is
in our on-disk pack, but _not_ adding it to our packlist
(which costs memory, and increases the search space for
deltas).
One complication is that if we're omitting some objects,
we can't set a delta against a base that we're not
sending. So we have to check each object in
try_partial_reuse() to make sure we have its delta.
About performance, in the worst case we might have
interleaved objects that we are sending or not sending,
and we'd have as many chunks as objects. But in practice
we send big chunks.
For instance, packing torvalds/linux on GitHub servers
now reused 6.5M objects, but only needed ~50k chunks.
Helped-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Let's refactor the way we check if an object is packed by
introducing obj_is_packed(). This function is now a simple
wrapper around packlist_find(), but it will evolve in a
following commit.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Let's make it possible to configure if we want pack reuse or not.
The main reason it might not be wanted is probably debugging and
performance testing, though pack reuse _might_ cause larger packs,
because we wouldn't consider the reused objects as bases for
finding new deltas.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Various fixes to codepaths gcc 9 had trouble following dataflow.
* jk/misc-uninitialized-fixes:
pack-objects: drop packlist index_pos optimization
test-read-cache: drop namelen variable
diff-delta: set size out-parameter to 0 for NULL delta
bulk-checkin: zero-initialize hashfile_checkpoint
pack-objects: use object_id in packlist_alloc()
git-am: handle missing "author" when parsing commit
xmalloc() used to have a mechanism to ditch memory and address
space resources as the last resort upon seeing an allocation
failure from the underlying malloc(), which made the code complex
and thread-unsafe with dubious benefit, as major memory resource
users already do limit their uses with various other mechanisms.
It has been simplified away.
* jk/drop-release-pack-memory:
packfile: drop release_pack_memory()
To see when packfile reuse kicks in or not, it is useful to
show reused packfile objects statistics in the output of
upload-pack.
Helped-by: James Ramsay <james@jramsay.com.au>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A mechanism to affect the default setting for a (related) group of
configuration variables is introduced.
* ds/feature-macros:
repo-settings: create feature.experimental setting
repo-settings: create feature.manyFiles setting
repo-settings: parse core.untrackedCache
commit-graph: turn on commit-graph by default
t6501: use 'git gc' in quiet mode
repo-settings: consolidate some config settings
Once upon a time, the code to add an object to our packing list in
pack-objects all lived in a single function. It computed the position
within the hash table once, then used it to check if the object was
already present, and if not, to add it.
Later, in 2834bc27c1 (pack-objects: refactor the packing list,
2013-10-24), this was split into two functions: packlist_find() and
packlist_alloc(). We ended up with an "index_pos" variable that gets
passed through several functions to make it from one to the other.
The resulting code is rather confusing to follow. The "index_pos"
variable is sometimes undefined, if we don't yet have a hash table. This
works out in practice because in that case packlist_alloc() won't use it
at all, since it will have to create/grow the hash table. But it's hard
to verify that, and it does cause gcc 9.2.1's -Wmaybe-uninitialized to
complain when compiled with "-flto -O3" (rightfully, since we do pass
the uninitialized value as a function parameter, even if nobody ends up
using it).
All of this is to save computing the hash index again when we're
inserting into the hash table, which I found doesn't make a measurable
difference in the program runtime (which is not surprising, since we're
doing all kinds of other heavyweight things for each object).
Let's just drop this index_pos variable entirely, simplifying the code
(and pleasing the compiler).
We might be better still refactoring this custom hash table to use one
of our existing implementations (an oidmap, or a kh_oid_map). I stopped
short of that here, but this would be the likely first step towards that
anyway.
Reported-by: Stephan Beyer <s-beyer@gmx.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The only caller of packlist_alloc() already has a "struct object_id",
and we immediately copy the hash they pass us into our own object_id.
Let's avoid the unnecessary round-trip to a raw sha1 pointer.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There are a few important config settings that are not loaded
during git_default_config. These are instead loaded on-demand.
Centralize these config options to a single scan, and store
all of the values in a repo_settings struct. The values for
each setting are initialized as negative to indicate "unset".
This centralization will be particularly important in a later
change to introduce "meta" config settings that change the
defaults for these config settings.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Long ago, in 97bfeb34df (Release pack windows before reporting out of
memory., 2006-12-24), we taught xmalloc() and friends to try unmapping
pack windows when malloc() failed. It's unlikely that his helps a lot in
practice, and it has some downsides. First, the downsides:
1. It makes xmalloc() not thread-safe. We've worked around this in
pack-objects.c, which installs its own locking version of the
try_to_free_routine(). But other threaded code doesn't.
2. It makes the system as a whole harder to reason about. Functions
which allocate heap memory under the hood may have farther-reaching
effects than expected.
That might be worth the tradeoff if there's a benefit. But in practice,
it seems unlikely. We're generally dealing with mmap'd files, so the OS
is going to do a much better job at responding to memory pressure by
dropping individual pages (the exception is systems with NO_MMAP, but
even there the OS can probably respond just as well with swapping).
So the only thing we're really freeing is address space. On 64-bit
systems, we have plenty of that to go around. On 32-bit systems, it
could possibly help. But around the same time we made two other changes:
77ccc5bbd1 (Introduce new config option for mmap limit., 2006-12-23) and
60bb8b1453 (Fully activate the sliding window pack access., 2006-12-23).
Together that means that a 32-bit system should have no more than 256MB
total of packed-git mmaps at one time, split between a few 32MB windows.
It's unlikely we have any address space problems since then, but we
don't have any data since the features were all added at the same time.
Likewise, xmmap() will try to free memory. At first glance, it seems
like we'd need this (when we try to mmap a new window, we might need to
close an old one to save address space on a 32-bit system). But we're
saved again by core.packedGitLimit: if we're going to exceed our 256MB
limit, we'll close an existing window before we even call mmap().
So it seems unlikely that this feature is actually doing anything
useful. And while we don't have reports of it harming anything (probably
because it rarely if ever kicks in), it would be nice to simplify the
system overall. This patch drops the whole try_to_free system from
xmalloc(), as well as the manual pack memory release in xmmap().
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Depending on various config options, a full repack may not be able to
build a reachability bitmap index (e.g., if pack.packSizeLimit forces us
to write multiple packs). In these cases pack-objects may write a
warning to stderr.
Since 36eba0323d (repack: enable bitmaps by default on bare repos,
2019-03-14), we may generate these warnings even when the user did not
explicitly ask for bitmaps. This has two downsides:
- it can be confusing, if they don't know what bitmaps are
- a daemonized auto-gc will write this to its log file, and the
presence of the warning may suppress further auto-gc (until
gc.logExpiry has elapsed)
Let's have repack communicate to pack-objects that the choice to turn on
bitmaps was not made explicitly by the user, which in turn allows
pack-objects to suppress these warnings.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The tree-walk API learned to pass an in-core repository
instance throughout more codepaths.
* nd/tree-walk-with-repo:
t7814: do not generate same commits in different repos
Use the right 'struct repository' instead of the_repository
match-trees.c: remove the_repo from shift_tree*()
tree-walk.c: remove the_repo from get_tree_entry_follow_symlinks()
tree-walk.c: remove the_repo from get_tree_entry()
tree-walk.c: remove the_repo from fill_tree_descriptor()
sha1-file.c: remove the_repo from read_object_with_reference()
Code clean-up to remove hardcoded SHA-1 hash from many places.
* jk/oidhash:
hashmap: convert sha1hash() to oidhash()
hash.h: move object_id definition from cache.h
khash: rename oid helper functions
khash: drop sha1-specific map types
pack-bitmap: convert khash_sha1 maps into kh_oid_map
delta-islands: convert island_marks khash to use oids
khash: rename kh_oid_t to kh_oid_set
khash: drop broken oid_map typedef
object: convert create_object() to use object_id
object: convert internal hash_obj() to object_id
object: convert lookup_object() to use object_id
object: convert lookup_unknown_object() to use object_id
pack-objects: convert locate_object_entry_hash() to object_id
pack-objects: convert packlist_find() to use object_id
pack-bitmap-write: convert some helpers to use object_id
upload-pack: rename a "sha1" variable to "oid"
describe: fix accidental oid/hash type-punning
The codepath to compute delta islands used to spew progress output
without giving the callers any way to squelch it, which has been
fixed.
* jk/delta-islands-progress-fix:
delta-islands: respect progress flag
The delta island code always prints "Marked %d islands", even if
progress has been suppressed with --no-progress or by sending stderr to
a non-tty.
Let's pass a progress boolean to load_delta_islands(). We already do
the same thing for the progress meter in resolve_tree_islands().
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There are no callers left of lookup_unknown_object() that aren't just
passing us the "hash" member of a "struct object_id". Let's take the
whole struct, which gets us closer to removing all raw sha1 variables.
It also matches the existing conversions of lookup_blob(), etc.
The conversions of callers were done by hand, but they're all mechanical
one-liners.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We take a raw hash pointer, but most of our callers have a "struct
object_id" already. Let's switch to taking the full struct, which will
let us continue removing uses of raw sha1 buffers.
There are two callers that do need special attention:
- in rebuild_existing_bitmaps(), we need to switch to
nth_packed_object_oid(). This incurs an extra hash copy over
pointing straight to the mmap'd sha1, but it shouldn't be measurable
compared to the rest of the operation.
- in can_reuse_delta() we already spent the effort to copy the sha1
into a "struct object_id", but now we just have to do so a little
earlier in the function (we can't easily convert that function's
callers because they may be pointing at mmap'd REF_DELTA blocks).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* jk/unused-params-final-batch:
verify-commit: simplify parameters to run_gpg_verify()
show-branch: drop unused parameter from show_independent()
rev-list: drop unused void pointer from finish_commit()
remove_all_fetch_refspecs(): drop unused "remote" parameter
receive-pack: drop unused "commands" from prepare_shallow_update()
pack-objects: drop unused rev_info parameters
name-rev: drop unused parameters from is_better_name()
mktree: drop unused length parameter
wt-status: drop unused status parameter
read-cache: drop unused parameter from threaded load
clone: drop dest parameter from copy_alternates()
submodule: drop unused prefix parameter from some functions
builtin: consistently pass cmd_* prefix to parse_options
cmd_{read,write}_tree: rename "unused" variable that is used
The code to generate the multi-pack idx file was not prepared to
see too many packfiles and ran out of open file descriptor, which
has been corrected.
* ds/midx-too-many-packs:
midx: add packs to packed_git linked list
midx: pass a repository pointer
The connectivity bitmaps are created by default in bare
repositories now; also the pathname hash-cache is created by
default to avoid making crappy deltas when repacking.
* ew/repack-with-bitmaps-by-default:
pack-objects: default to writing bitmap hash-cache
t5310: correctly remove bitmaps for jgit test
repack: enable bitmaps by default on bare repos
When collecting the list of objects to pack in get_object_list(), we
pass our rev_info struct around to some functions that don't need it.
This is due to 03a9683d22 (Simplify is_kept_pack(), 2009-02-28), where
the kept-pack handling was moved out of the revision machinery.
Let's drop these unused parameters.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The "git pack-objects" command learned to report the number of
objects it packed via the trace2 mechanism.
* jk/pack-objects-reports-num-objects-to-trace2:
pack-objects: write objects packed to trace2
Much of the multi-pack-index code focuses on the multi_pack_index
struct, and so we only pass a pointer to the current one. However,
we will insert a dependency on the packed_git linked list in a
future change, so we will need a repository reference. Inserting
these parameters is a significant enough change to split out.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This is useful when investigating performance of pushes, and other times
when no progress information is written (because the pack is written to
stdout).
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Instead of storing unsigned char pointers in the hash tables, switch to
storing instances of struct object_id. Update several internal functions
and one external function to take pointers to struct object_id.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Enabling pack.writebitmaphashcache should always be a performance win.
It costs only 4 bytes per object on disk, and the timings in ae4f07fbcc
(pack-bitmap: implement optional name_hash cache, 2013-12-21) show it
improving fetch and partial-bitmap clone times by 40-50%.
The only reason we didn't enable it by default at the time is that early
versions of JGit's bitmap reader complained about the presence of
optional header bits it didn't understand. But that was changed in
JGit's d2fa3987a (Use bitcheck to check for presence of OPT_FULL option,
2013-10-30), which made it into JGit v3.5.0 in late 2014.
So let's turn this option on by default. It's backwards-compatible with
all versions of Git, and if you are also using JGit on the same
repository, you'd only run into problems using a version that's almost 5
years old.
We'll drop the manual setting from all of our test scripts, including
perf tests. This isn't strictly necessary, but it has two advantages:
1. If the hash-cache ever stops being enabled by default, our perf
regression tests will notice.
2. We can use the modified perf tests to show off the behavior of an
otherwise unconfigured repo, as shown below.
These are the results of a few of a perf tests against linux.git that
showed interesting results. You can see the expected speedup in 5310.4,
which was noted in ae4f07fbcc. Curiously, 5310.8 did not improve (and
actually got slower), despite seeing the opposite in ae4f07fbcc.
I don't have an explanation for that.
The tests from p5311 did not exist back then, but do show improvements
(a smaller pack due to better deltas, which we found in less time).
Test HEAD^ HEAD
-------------------------------------------------------------------------------------
5310.4: simulated fetch 7.39(22.70+0.25) 5.64(11.43+0.22) -23.7%
5310.8: clone (partial bitmap) 18.45(24.83+1.19) 19.94(28.40+1.36) +8.1%
5311.31: server (128 days) 0.41(1.13+0.05) 0.34(0.72+0.02) -17.1%
5311.32: size (128 days) 7.4M 7.0M -4.8%
5311.33: client (128 days) 1.33(1.49+0.06) 1.29(1.37+0.12) -3.0%
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When studying the performance of 'git push' we would like to know
how much time is spent at various parts of the command. One area
that could cause performance trouble is 'git pack-objects'.
Add trace2 regions around the three main actions taken in this
command:
1. Enumerate objects.
2. Prepare pack.
3. Write pack-file.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"git pack-objects" learned another algorithm to compute the set of
objects to send, that trades the resulting packfile off to save
traversal cost to favor small pushes.
* ds/push-sparse-tree-walk:
pack-objects: create GIT_TEST_PACK_SPARSE
pack-objects: create pack.useSparse setting
revision: implement sparse algorithm
list-objects: consume sparse tree walk
revision: add mark_tree_uninteresting_sparse
The assumption to work on the single "in-core index" instance has
been reduced from the library-ish part of the codebase.
* nd/the-index-final:
cache.h: flip NO_THE_INDEX_COMPATIBILITY_MACROS switch
read-cache.c: remove the_* from index_has_changes()
merge-recursive.c: remove implicit dependency on the_repository
merge-recursive.c: remove implicit dependency on the_index
sha1-name.c: remove implicit dependency on the_index
read-cache.c: replace update_index_if_able with repo_&
read-cache.c: kill read_index()
checkout: avoid the_index when possible
repository.c: replace hold_locked_index() with repo_hold_locked_index()
notes-utils.c: remove the_repository references
grep: use grep_opt->repo instead of explict repo argument
"git pack-objects" incorrectly used uninitialized mutex, which has
been corrected.
* ph/pack-objects-mutex-fix:
pack-objects: merge read_lock and lock in packing_data struct
pack-objects: move read mutex to packing_data struct
The code to walk tree objects has been taught that we may be
working with object names that are not computed with SHA-1.
* bc/tree-walk-oid:
cache: make oidcpy always copy GIT_MAX_RAWSZ bytes
tree-walk: store object_id in a separate member
match-trees: use hashcpy to splice trees
match-trees: compute buffer offset correctly when splicing
tree-walk: copy object ID before use
Rename the packing_data lock to obd_lock and upgrade it to a recursive
mutex to make it suitable for current read_lock usages. Additionally
remove the superfluous #ifndef NO_PTHREADS guard around mutex
initialization in prepare_packing_data as the mutex functions
themselves are already protected.
Signed-off-by: Patrick Hogg <phogg@novamoon.net>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
ac77d0c37 ("pack-objects: shrink size field in struct object_entry",
2018-04-14) added an extra usage of read_lock/read_unlock in the newly
introduced oe_get_size_slow for thread safety in parallel calls to
try_delta(). Unfortunately oe_get_size_slow is also used in serial
code, some of which is called before the first invocation of
ll_find_deltas. As such the read mutex is not guaranteed to be
initialized.
Resolve this by moving the read mutex to packing_data and initializing
it in prepare_packing_data which is initialized in cmd_pack_objects.
Signed-off-by: Patrick Hogg <phogg@novamoon.net>
Reviewed-by: Duy Nguyen <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
By default, index compat macros are off from now on, because they
could hide the_index dependency.
Only those in builtin can use it.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Create a test variable GIT_TEST_PACK_SPARSE to enable the sparse
object walk algorithm by default during the test suite. Enabling
this variable ensures coverage in many interesting cases, such as
shallow clones, partial clones, and missing objects.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The '--sparse' flag in 'git pack-objects' changes the algorithm
used to enumerate objects to one that is faster for individual
users pushing new objects that change only a small cone of the
working directory. The sparse algorithm is not recommended for a
server, which likely sends new objects that appear across the
entire working directory.
Create a 'pack.useSparse' setting that enables this new algorithm.
This allows 'git push' to use this algorithm without passing a
'--sparse' flag all the way through four levels of run_command()
calls.
If the '--no-sparse' flag is set, then this config setting is
overridden.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When creating a pack-file using 'git pack-objects --revs' we provide
a list of interesting and uninteresting commits. For example, a push
operation would make the local topic branch be interesting and the
known remote refs as uninteresting. We want to discover the set of
new objects to send to the server as a thin pack.
We walk these commits until we discover a frontier of commits such
that every commit walk starting at interesting commits ends in a root
commit or unintersting commit. We then need to discover which
non-commit objects are reachable from uninteresting commits. This
commit walk is not changing during this series.
The mark_edges_uninteresting() method in list-objects.c iterates on
the commit list and does the following:
* If the commit is UNINTERSTING, then mark its root tree and every
object it can reach as UNINTERESTING.
* If the commit is interesting, then mark the root tree of every
UNINTERSTING parent (and all objects that tree can reach) as
UNINTERSTING.
At the very end, we repeat the process on every commit directly
given to the revision walk from stdin. This helps ensure we properly
cover shallow commits that otherwise were not included in the
frontier.
The logic to recursively follow trees is in the
mark_tree_uninteresting() method in revision.c. The algorithm avoids
duplicate work by not recursing into trees that are already marked
UNINTERSTING.
Add a new 'sparse' option to the mark_edges_uninteresting() method
that performs this logic in a slightly different way. As we iterate
over the commits, we add all of the root trees to an oidset. Then,
call mark_trees_uninteresting_sparse() on that oidset. Note that we
include interesting trees in this process. The current implementation
of mark_trees_unintersting_sparse() will walk the same trees as
the old logic, but this will be replaced in a later change.
Add a '--sparse' flag in 'git pack-objects' to call this new logic.
Add a new test script t/t5322-pack-objects-sparse.sh that tests this
option. The tests currently demonstrate that the resulting object
list is the same as the old algorithm. This includes a case where
both algorithms pack an object that is not needed by a remote due to
limits on the explored set of trees. When the sparse algorithm is
changed in a later commit, we will add a test that demonstrates a
change of behavior in some cases.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
