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2014-10-29Merge branch 'jk/prune-mtime'Libravatar Junio C Hamano1-15/+71
Tighten the logic to decide that an unreachable cruft is sufficiently old by covering corner cases such as an ancient object becoming reachable and then going unreachable again, in which case its retention period should be prolonged. * jk/prune-mtime: (28 commits) drop add_object_array_with_mode revision: remove definition of unused 'add_object' function pack-objects: double-check options before discarding objects repack: pack objects mentioned by the index pack-objects: use argv_array reachable: use revision machinery's --indexed-objects code rev-list: add --indexed-objects option rev-list: document --reflog option t5516: test pushing a tag of an otherwise unreferenced blob traverse_commit_list: support pending blobs/trees with paths make add_object_array_with_context interface more sane write_sha1_file: freshen existing objects pack-objects: match prune logic for discarding objects pack-objects: refactor unpack-unreachable expiration check prune: keep objects reachable from recent objects sha1_file: add for_each iterators for loose and packed objects count-objects: use for_each_loose_file_in_objdir count-objects: do not use xsize_t when counting object size prune-packed: use for_each_loose_file_in_objdir reachable: mark index blobs as SEEN ...
2014-10-24Merge branch 'eb/no-pthreads'Libravatar Junio C Hamano1-2/+4
Allow us build with NO_PTHREADS=NoThanks compilation option. * eb/no-pthreads: Handle atexit list internaly for unthreaded builds pack-objects: set number of threads before checking and warning index-pack: fix compilation with NO_PTHREADS
2014-10-24Merge branch 'jk/pack-objects-no-bitmap-when-splitting'Libravatar Junio C Hamano1-0/+1
Splitting pack-objects output into multiple packs is incompatible with the use of reachability bitmap. * jk/pack-objects-no-bitmap-when-splitting: pack-objects: turn off bitmaps when we split packs
2014-10-19pack-objects: turn off bitmaps when we split packsLibravatar Jeff King1-0/+1
If a pack.packSizeLimit is set, we may split the pack data across multiple packfiles. This means we cannot generate .bitmap files, as they require that all of the reachable objects are in the same pack. We check that condition when we are generating the list of objects to pack (and disable bitmaps if we are not packing everything), but we forgot to update it when we notice that we needed to split (which doesn't happen until the actual write phase). The resulting bitmaps are quite bogus (they mention entries that do not exist in the pack!) and can cause a fetch or push to send insufficient objects. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-19pack-objects: double-check options before discarding objectsLibravatar Jeff King1-0/+2
When we are given an expiration time like --unpack-unreachable=2.weeks.ago, we avoid writing out old, unreachable loose objects entirely, under the assumption that running "prune" would simply delete them immediately anyway. However, this is only valid if we computed the same set of reachable objects as prune would. In practice, this is the case, because only git-repack uses the --unpack-unreachable option with an expiration, and it always feeds as many objects into the pack as possible. But we can double-check at runtime just to be sure. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-19repack: pack objects mentioned by the indexLibravatar Jeff King1-0/+8
When we pack all objects, we use only the objects reachable from references and reflogs. This misses any objects which are reachable from the index, but not yet referenced. By itself this isn't a big deal; the objects can remain loose until they are actually used in a commit. However, it does create a problem when we drop packed but unreachable objects. We try to optimize out the writing of objects that we will immediately prune, which means we must follow the same rules as prune in determining what is reachable. And prune uses the index for this purpose. This is rather uncommon in practice, as objects in the index would not usually have been packed in the first place. But it could happen in a sequence like: 1. You make a commit on a branch that references blob X. 2. You repack, moving X into the pack. 3. You delete the branch (and its reflog), so that X is unreferenced. 4. You "git add" blob X so that it is now referenced only by the index. 5. You repack again with git-gc. The pack-objects we invoke will see that X is neither referenced nor recent and not bother loosening it. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-19pack-objects: use argv_arrayLibravatar Jeff King1-10/+10
This saves us from having to bump the rp_av count when we add new traversal options. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-16pack-objects: match prune logic for discarding objectsLibravatar Jeff King1-0/+39
A recent commit taught git-prune to keep non-recent objects that are reachable from recent ones. However, pack-objects, when loosening unreachable objects, tries to optimize out the write in the case that the object will be immediately pruned. It now gets this wrong, since its rule does not reflect the new prune code (and this can be seen by running t6501 with a strategically placed repack). Let's teach pack-objects similar logic. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-16pack-objects: refactor unpack-unreachable expiration checkLibravatar Jeff King1-5/+12
When we are loosening unreachable packed objects, we do not bother to process objects that would simply be pruned immediately anyway. The "would be pruned" check is a simple comparison, but is about to get more complicated. Let's pull it out into a separate function. Note that this is slightly less efficient than the original, which avoided even opening old packs, since no object in them could pass the current check, which cares only about the pack mtime. But the new rules will depend on the exact object, so we need to perform the check even for old packs. Note also that we fix a minor buglet when the pack mtime is exactly the same as the expiration time. The prune code considers that worth pruning, whereas our check here considered it worth keeping. This wasn't a big deal. Besides being unlikely to happen, the result was simply that the object was loosened and then pruned, missing the optimization. Still, we can easily fix it while we are here. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-13pack-objects: set number of threads before checking and warningLibravatar Junio C Hamano1-2/+4
Under NO_PTHREADS build, we warn when delta_search_threads is not set to 1, because that is the only sensible value on a single threaded build. However, the auto detection that kicks in when that variable is set to 0 (e.g. there is no configuration variable or command line option, or an explicit --threads=0 is given from the command line to override the pack.threads configuration to force auto-detection) was not done before the condition to issue this warning was tested. Move the auto-detection code and place it at an appropriate spot. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-09-18use REALLOC_ARRAY for changing the allocation size of arraysLibravatar René Scharfe1-2/+1
Signed-off-by: Rene Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-08-26Merge branch 'jk/pack-shallow-always-without-bitmap'Libravatar Junio C Hamano1-0/+1
Reachability bitmaps do not work with shallow operations. Fixes regression in 2.0. * jk/pack-shallow-always-without-bitmap: pack-objects: turn off bitmaps when we see --shallow lines
2014-08-12pack-objects: turn off bitmaps when we see --shallow linesLibravatar Jeff King1-0/+1
Reachability bitmaps do not work with shallow operations, because they cache a view of the object reachability that represents the true objects. Whereas a shallow repository (or a shallow operation in a repository) is inherently cutting off the object graph with a graft. We explicitly disallow the use of bitmaps in shallow repositories by checking is_repository_shallow(), and we should continue to do that. However, we also want to disallow bitmaps when we are serving a fetch to a shallow client, since we momentarily take on their grafted view of the world. It used to be enough to call is_repository_shallow at the start of pack-objects. Upload-pack wrote the other side's shallow state to a temporary file and pointed the whole pack-objects process at this state with "git --shallow-file", and from the perspective of pack-objects, we really were in a shallow repo. But since b790e0f (upload-pack: send shallow info over stdin to pack-objects, 2014-03-11), we do it differently: we send --shallow lines to pack-objects over stdin, and it registers them itself. This means that our is_repository_shallow check is way too early (we have not been told about the shallowness yet), and that it is insufficient (calling is_repository_shallow is not enough, as the shallow grafts we register do not change its return value). Instead, we can just turn off bitmaps explicitly when we see these lines. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-25Merge branch 'jk/repack-pack-writebitmaps-config'Libravatar Junio C Hamano1-4/+0
* jk/repack-pack-writebitmaps-config: t7700: drop explicit --no-pack-kept-objects from .keep test repack: introduce repack.writeBitmaps config option repack: simplify handling of --write-bitmap-index pack-objects: stop respecting pack.writebitmaps
2014-06-10pack-objects: stop respecting pack.writebitmapsLibravatar Jeff King1-4/+0
The handling of the pack.writebitmaps config option originally happened in pack-objects, which is quite low-level. It would make more sense for drivers of pack-objects to read the config, and then manipulate pack-objects with command-line options. Recently, repack learned to do so, making the low-level read of pack.writebitmaps redundant here. Other callers, like upload-pack, would not generally want to write bitmaps anyway. This could be considered a regression for somebody who is driving pack-objects themselves outside of repack and expects the config option to be used. However, such users seem rather unlikely given how new the bitmap code is (and the fact that they would basically be reimplementing repack in the first place). Note that we do not do anything with pack.writeBitmapHashCache here. That option is not about "do we write bimaps", but rather "when we are writing bitmaps, how do we do it?". You would want that to kick in anytime you decide to write them, similar to how pack.indexVersion is used. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-08Merge branch 'jk/pack-bitmap'Libravatar Junio C Hamano1-1/+12
* jk/pack-bitmap: pack-objects: do not reuse packfiles without --delta-base-offset add `ignore_missing_links` mode to revwalk
2014-04-08Merge branch 'jl/nor-or-nand-and'Libravatar Junio C Hamano1-1/+1
Eradicate mistaken use of "nor" (that is, essentially "nor" used not in "neither A nor B" ;-)) from in-code comments, command output strings, and documentations. * jl/nor-or-nand-and: code and test: fix misuses of "nor" comments: fix misuses of "nor" contrib: fix misuses of "nor" Documentation: fix misuses of "nor"
2014-04-04pack-objects: do not reuse packfiles without --delta-base-offsetLibravatar Jeff King1-1/+12
When we are sending a packfile to a remote, we currently try to reuse a whole chunk of packfile without bothering to look at the individual objects. This can make things like initial clones much lighter on the server, as we can just dump the packfile bytes. However, it's possible that the other side cannot read our packfile verbatim. For example, we may have objects stored as OFS_DELTA, but the client is an antique version of git that only understands REF_DELTA. We negotiate this capability over the fetch protocol. A normal pack-objects run will convert OFS_DELTA into REF_DELTA on the fly, but the "reuse pack" code path never even looks at the objects. This patch disables packfile reuse if the other side is missing any capabilities that we might have used in the on-disk pack. Right now the only one is OFS_DELTA, but we may need to expand in the future (e.g., if packv4 introduces new object types). We could be more thorough and only disable reuse in this case when we actually have an OFS_DELTA to send, but: 1. We almost always will have one, since we prefer OFS_DELTA to REF_DELTA when possible. So this case would almost never come up. 2. Looking through the objects defeats the purpose of the optimization, which is to do as little work as possible to get the bytes to the remote. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-03-31comments: fix misuses of "nor"Libravatar Justin Lebar1-1/+1
Signed-off-by: Justin Lebar <jlebar@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-03-28Merge branch 'jk/pack-bitmap-progress'Libravatar Junio C Hamano1-11/+19
The progress output while repacking and transferring objects showed an apparent large silence while writing the objects out of existing packfiles, when the reachability bitmap was in use. * jk/pack-bitmap-progress: pack-objects: show reused packfile objects in "Counting objects" pack-objects: show progress for reused packfiles
2014-03-28Merge branch 'jk/pack-bitmap'Libravatar Junio C Hamano1-1/+11
Instead of dying when asked to (re)pack with the reachability bitmap when a bitmap cannot be built, just (re)pack without producing a bitmap in such a case, with a warning. * jk/pack-bitmap: pack-objects: turn off bitmaps when skipping objects
2014-03-21Merge branch 'nd/upload-pack-shallow'Libravatar Junio C Hamano1-0/+10
Serving objects from a shallow repository needs to write a temporary file to be used, but the serving upload-pack may not have write access to the repository which is meant to be read-only. Instead feed these temporary shallow bounds from the standard input of pack-objects so that we do not have to use a temporary file. * nd/upload-pack-shallow: upload-pack: send shallow info over stdin to pack-objects
2014-03-18Merge branch 'sh/finish-tmp-packfile'Libravatar Junio C Hamano1-9/+6
* sh/finish-tmp-packfile: finish_tmp_packfile():use strbuf for pathname construction
2014-03-18Merge branch 'dd/use-alloc-grow'Libravatar Junio C Hamano1-6/+3
Replace open-coded reallocation with ALLOC_GROW() macro. * dd/use-alloc-grow: sha1_file.c: use ALLOC_GROW() in pretend_sha1_file() read-cache.c: use ALLOC_GROW() in add_index_entry() builtin/mktree.c: use ALLOC_GROW() in append_to_tree() attr.c: use ALLOC_GROW() in handle_attr_line() dir.c: use ALLOC_GROW() in create_simplify() reflog-walk.c: use ALLOC_GROW() replace_object.c: use ALLOC_GROW() in register_replace_object() patch-ids.c: use ALLOC_GROW() in add_commit() diffcore-rename.c: use ALLOC_GROW() diff.c: use ALLOC_GROW() commit.c: use ALLOC_GROW() in register_commit_graft() cache-tree.c: use ALLOC_GROW() in find_subtree() bundle.c: use ALLOC_GROW() in add_to_ref_list() builtin/pack-objects.c: use ALLOC_GROW() in check_pbase_path()
2014-03-17pack-objects: turn off bitmaps when skipping objectsLibravatar Jeff King1-1/+11
The pack bitmap format requires that we have a single bit for each object in the pack, and that each object's bitmap represents its complete set of reachable objects. Therefore we have no way to represent the bitmap of an object which references objects outside the pack. We notice this problem while generating the bitmaps, as we try to find the offset of a particular object and realize that we do not have it. In this case we die, and neither the bitmap nor the pack is generated. This is correct, but perhaps a little unfriendly. If you have bitmaps turned on in the config, many repacks will fail which would otherwise succeed. E.g., incremental repacks, repacks with "-l" when you have alternates, ".keep" files. Instead, this patch notices early that we are omitting some objects from the pack and turns off bitmaps (with a warning). Note that this is not strictly correct, as it's possible that the object being omitted is not reachable from any other object in the pack. In practice, this is almost never the case, and there are two advantages to doing it this way: 1. The code is much simpler, as we do not have to cleanly abort the bitmap-generation process midway through. 2. We do not waste time partially generating bitmaps only to find out that some object deep in the history is not being packed. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-03-17pack-objects: show reused packfile objects in "Counting objects"Libravatar Jeff King1-8/+3
When we are sending a pack for push or fetch, we may reuse a chunk of packfile without even parsing it. The progress meter then looks like this: Reusing existing pack: 3440489, done. Counting objects: 3, done. The first line shows that we are reusing a large chunk of objects, and then we further count any objects not included in the reused portion with an actual traversal. These are all implementation details that the user does not need to care about. Instead, we can show the reused objects in the normal "counting..." progress meter (which will simply go much faster than normal), and then continue to add to it as we traverse. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-03-17pack-objects: show progress for reused packfilesLibravatar Jeff King1-3/+16
When the "--all-progress" option is in effect, pack-objects shows a progress report for the "writing" phase. If the repository has bitmaps and we are reusing a packfile, the user sees no progress update until the whole packfile is sent. Since this is typically the bulk of what is being written, it can look like git hangs during this phase, even though the transfer is proceeding. This generally only happens with "git push" from a repository with bitmaps. We do not use "--all-progress" for fetch (since the result is going to index-pack on the client, which takes care of progress reporting). And for regular repacks to disk, we do not reuse packfiles. We already have the progress meter setup during write_reused_pack; we just need to call display_progress whiel we are writing out the pack. The progress meter is attached to our output descriptor, so it automatically handles the throughput measurements. However, we need to update the object count as we go, since that is what feeds the percentage we show. We aren't actually parsing the packfile as we send it, so we have no idea how many objects we have sent; we only know that at the end of N bytes, we will have sent M objects. So we cheat a little and assume each object is M/N bytes (i.e., the mean of the objects we are sending). While this isn't strictly true, it actually produces a more pleasing progress meter for the user, as it moves smoothly and predictably (and nobody really cares about the object count; they care about the percentage, and the object count is a proxy for that). One alternative would be to actually show two progress meters: one for the reused pack, and one for the rest of the objects. That would more closely reflect the data we have (the first would be measured in bytes, and the second measured in objects). But it would also be more complex and annoying to the user; rather than seeing one progress meter counting up to 100%, they would finish one meter, then start another one at zero. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-03-14Merge branch 'sh/write-pack-file-warning-message-fix'Libravatar Junio C Hamano1-1/+1
A warning from "git pack-objects" were generated by referring to an incorrect variable when forming the filename that we had trouble with. * sh/write-pack-file-warning-message-fix: write_pack_file: use correct variable in diagnostic
2014-03-14Merge branch 'mh/replace-refs-variable-rename'Libravatar Junio C Hamano1-1/+1
* mh/replace-refs-variable-rename: Document some functions defined in object.c Add docstrings for lookup_replace_object() and do_lookup_replace_object() rename read_replace_refs to check_replace_refs
2014-03-14Merge branch 'nd/i18n-progress'Libravatar Junio C Hamano1-3/+3
Mark the progress indicators from various time-consuming commands for i18n/l10n. * nd/i18n-progress: i18n: mark all progress lines for translation
2014-03-11upload-pack: send shallow info over stdin to pack-objectsLibravatar Nguyễn Thái Ngọc Duy1-0/+10
Before cdab485 (upload-pack: delegate rev walking in shallow fetch to pack-objects - 2013-08-16) upload-pack does not write to the source repository. cdab485 starts to write $GIT_DIR/shallow_XXXXXX if it's a shallow fetch, so the source repo must be writable. git:// servers do not need write access to repos and usually don't have it, which means cdab485 breaks shallow clone over git:// Instead of using a temporary file as the media for shallow points, we can send them over stdin to pack-objects as well. Prepend shallow SHA-1 with --shallow so pack-objects knows what is what. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-03-03builtin/pack-objects.c: use ALLOC_GROW() in check_pbase_path()Libravatar Dmitry S. Dolzhenko1-6/+3
Signed-off-by: Dmitry S. Dolzhenko <dmitrys.dolzhenko@yandex.ru> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-03-03finish_tmp_packfile():use strbuf for pathname constructionLibravatar Sun He1-9/+6
The old version fixes a maximum length on the buffer, which could be a problem if one is not certain of the length of get_object_directory(). Using strbuf can avoid the protential bug. Helped-by: Michael Haggerty <mhagger@alum.mit.edu> Helped-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Sun He <sunheehnus@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-03-03Merge branch 'sh/write-pack-file-warning-message-fix' into ↵Libravatar Junio C Hamano1-1/+1
sh/finish-tmp-packfile * sh/write-pack-file-warning-message-fix: write_pack_file: use correct variable in diagnostic
2014-03-03write_pack_file: use correct variable in diagnosticLibravatar Sun He1-1/+1
'pack_tmp_name' is the subject of the utime() check, so report it in the warning, not the uninitialized 'tmpname' Signed-off-by: Sun He <sunheehnus@gmail.com> Reviewed-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-02-27Merge branch 'jk/pack-bitmap'Libravatar Junio C Hamano1-170/+281
Borrow the bitmap index into packfiles from JGit to speed up enumeration of objects involved in a commit range without having to fully traverse the history. * jk/pack-bitmap: (26 commits) ewah: unconditionally ntohll ewah data ewah: support platforms that require aligned reads read-cache: use get_be32 instead of hand-rolled ntoh_l block-sha1: factor out get_be and put_be wrappers do not discard revindex when re-preparing packfiles pack-bitmap: implement optional name_hash cache t/perf: add tests for pack bitmaps t: add basic bitmap functionality tests count-objects: recognize .bitmap in garbage-checking repack: consider bitmaps when performing repacks repack: handle optional files created by pack-objects repack: turn exts array into array-of-struct repack: stop using magic number for ARRAY_SIZE(exts) pack-objects: implement bitmap writing rev-list: add bitmap mode to speed up object lists pack-objects: use bitmaps when packing objects pack-objects: split add_object_entry pack-bitmap: add support for bitmap indexes documentation: add documentation for the bitmap format ewah: compressed bitmap implementation ...
2014-02-24i18n: mark all progress lines for translationLibravatar Nguyễn Thái Ngọc Duy1-3/+3
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-02-20rename read_replace_refs to check_replace_refsLibravatar Michael Haggerty1-1/+1
The semantics of this flag was changed in commit e1111cef23 inline lookup_replace_object() calls but wasn't renamed at the time to minimize code churn. Rename it now, and add a comment explaining its use. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-30pack-bitmap: implement optional name_hash cacheLibravatar Vicent Marti1-1/+9
When we use pack bitmaps rather than walking the object graph, we end up with the list of objects to include in the packfile, but we do not know the path at which any tree or blob objects would be found. In a recently packed repository, this is fine. A fetch would use the paths only as a heuristic in the delta compression phase, and a fully packed repository should not need to do much delta compression. As time passes, though, we may acquire more objects on top of our large bitmapped pack. If clients fetch frequently, then they never even look at the bitmapped history, and all works as usual. However, a client who has not fetched since the last bitmap repack will have "have" tips in the bitmapped history, but "want" newer objects. The bitmaps themselves degrade gracefully in this circumstance. We manually walk the more recent bits of history, and then use bitmaps when we hit them. But we would also like to perform delta compression between the newer objects and the bitmapped objects (both to delta against what we know the user already has, but also between "new" and "old" objects that the user is fetching). The lack of pathnames makes our delta heuristics much less effective. This patch adds an optional cache of the 32-bit name_hash values to the end of the bitmap file. If present, a reader can use it to match bitmapped and non-bitmapped names during delta compression. Here are perf results for p5310: Test origin/master HEAD^ HEAD ------------------------------------------------------------------------------------------------- 5310.2: repack to disk 36.81(37.82+1.43) 47.70(48.74+1.41) +29.6% 47.75(48.70+1.51) +29.7% 5310.3: simulated clone 30.78(29.70+2.14) 1.08(0.97+0.10) -96.5% 1.07(0.94+0.12) -96.5% 5310.4: simulated fetch 3.16(6.10+0.08) 3.54(10.65+0.06) +12.0% 1.70(3.07+0.06) -46.2% 5310.6: partial bitmap 36.76(43.19+1.81) 6.71(11.25+0.76) -81.7% 4.08(6.26+0.46) -88.9% You can see that the time spent on an incremental fetch goes down, as our delta heuristics are able to do their work. And we save time on the partial bitmap clone for the same reason. Signed-off-by: Vicent Marti <tanoku@gmail.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-30pack-objects: implement bitmap writingLibravatar Vicent Marti1-0/+53
This commit extends more the functionality of `pack-objects` by allowing it to write out a `.bitmap` index next to any written packs, together with the `.idx` index that currently gets written. If bitmap writing is enabled for a given repository (either by calling `pack-objects` with the `--write-bitmap-index` flag or by having `pack.writebitmaps` set to `true` in the config) and pack-objects is writing a packfile that would normally be indexed (i.e. not piping to stdout), we will attempt to write the corresponding bitmap index for the packfile. Bitmap index writing happens after the packfile and its index has been successfully written to disk (`finish_tmp_packfile`). The process is performed in several steps: 1. `bitmap_writer_set_checksum`: this call stores the partial checksum for the packfile being written; the checksum will be written in the resulting bitmap index to verify its integrity 2. `bitmap_writer_build_type_index`: this call uses the array of `struct object_entry` that has just been sorted when writing out the actual packfile index to disk to generate 4 type-index bitmaps (one for each object type). These bitmaps have their nth bit set if the given object is of the bitmap's type. E.g. the nth bit of the Commits bitmap will be 1 if the nth object in the packfile index is a commit. This is a very cheap operation because the bitmap writing code has access to the metadata stored in the `struct object_entry` array, and hence the real type for each object in the packfile. 3. `bitmap_writer_reuse_bitmaps`: if there exists an existing bitmap index for one of the packfiles we're trying to repack, this call will efficiently rebuild the existing bitmaps so they can be reused on the new index. All the existing bitmaps will be stored in a `reuse` hash table, and the commit selection phase will prioritize these when selecting, as they can be written directly to the new index without having to perform a revision walk to fill the bitmap. This can greatly speed up the repack of a repository that already has bitmaps. 4. `bitmap_writer_select_commits`: if bitmap writing is enabled for a given `pack-objects` run, the sequence of commits generated during the Counting Objects phase will be stored in an array. We then use that array to build up the list of selected commits. Writing a bitmap in the index for each object in the repository would be cost-prohibitive, so we use a simple heuristic to pick the commits that will be indexed with bitmaps. The current heuristics are a simplified version of JGit's original implementation. We select a higher density of commits depending on their age: the 100 most recent commits are always selected, after that we pick 1 commit of each 100, and the gap increases as the commits grow older. On top of that, we make sure that every single branch that has not been merged (all the tips that would be required from a clone) gets their own bitmap, and when selecting commits between a gap, we tend to prioritize the commit with the most parents. Do note that there is no right/wrong way to perform commit selection; different selection algorithms will result in different commits being selected, but there's no such thing as "missing a commit". The bitmap walker algorithm implemented in `prepare_bitmap_walk` is able to adapt to missing bitmaps by performing manual walks that complete the bitmap: the ideal selection algorithm, however, would select the commits that are more likely to be used as roots for a walk in the future (e.g. the tips of each branch, and so on) to ensure a bitmap for them is always available. 5. `bitmap_writer_build`: this is the computationally expensive part of bitmap generation. Based on the list of commits that were selected in the previous step, we perform several incremental walks to generate the bitmap for each commit. The walks begin from the oldest commit, and are built up incrementally for each branch. E.g. consider this dag where A, B, C, D, E, F are the selected commits, and a, b, c, e are a chunk of simplified history that will not receive bitmaps. A---a---B--b--C--c--D \ E--e--F We start by building the bitmap for A, using A as the root for a revision walk and marking all the objects that are reachable until the walk is over. Once this bitmap is stored, we reuse the bitmap walker to perform the walk for B, assuming that once we reach A again, the walk will be terminated because A has already been SEEN on the previous walk. This process is repeated for C, and D, but when we try to generate the bitmaps for E, we can reuse neither the current walk nor the bitmap we have generated so far. What we do now is resetting both the walk and clearing the bitmap, and performing the walk from scratch using E as the origin. This new walk, however, does not need to be completed. Once we hit B, we can lookup the bitmap we have already stored for that commit and OR it with the existing bitmap we've composed so far, allowing us to limit the walk early. After all the bitmaps have been generated, another iteration through the list of commits is performed to find the best XOR offsets for compression before writing them to disk. Because of the incremental nature of these bitmaps, XORing one of them with its predecesor results in a minimal "bitmap delta" most of the time. We can write this delta to the on-disk bitmap index, and then re-compose the original bitmaps by XORing them again when loaded. This is a phase very similar to pack-object's `find_delta` (using bitmaps instead of objects, of course), except the heuristics have been greatly simplified: we only check the 10 bitmaps before any given one to find best compressing one. This gives good results in practice, because there is locality in the ordering of the objects (and therefore bitmaps) in the packfile. 6. `bitmap_writer_finish`: the last step in the process is serializing to disk all the bitmap data that has been generated in the two previous steps. The bitmap is written to a tmp file and then moved atomically to its final destination, using the same process as `pack-write.c:write_idx_file`. Signed-off-by: Vicent Marti <tanoku@gmail.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-30pack-objects: use bitmaps when packing objectsLibravatar Vicent Marti1-0/+107
In this patch, we use the bitmap API to perform the `Counting Objects` phase in pack-objects, rather than a traditional walk through the object graph. For a reasonably-packed large repo, the time to fetch and clone is often dominated by the full-object revision walk during the Counting Objects phase. Using bitmaps can reduce the CPU time required on the server (and therefore start sending the actual pack data with less delay). For bitmaps to be used, the following must be true: 1. We must be packing to stdout (as a normal `pack-objects` from `upload-pack` would do). 2. There must be a .bitmap index containing at least one of the "have" objects that the client is asking for. 3. Bitmaps must be enabled (they are enabled by default, but can be disabled by setting `pack.usebitmaps` to false, or by using `--no-use-bitmap-index` on the command-line). If any of these is not true, we fall back to doing a normal walk of the object graph. Here are some sample timings from a full pack of `torvalds/linux` (i.e. something very similar to what would be generated for a clone of the repository) that show the speedup produced by various methods: [existing graph traversal] $ time git pack-objects --all --stdout --no-use-bitmap-index \ </dev/null >/dev/null Counting objects: 3237103, done. Compressing objects: 100% (508752/508752), done. Total 3237103 (delta 2699584), reused 3237103 (delta 2699584) real 0m44.111s user 0m42.396s sys 0m3.544s [bitmaps only, without partial pack reuse; note that pack reuse is automatic, so timing this required a patch to disable it] $ time git pack-objects --all --stdout </dev/null >/dev/null Counting objects: 3237103, done. Compressing objects: 100% (508752/508752), done. Total 3237103 (delta 2699584), reused 3237103 (delta 2699584) real 0m5.413s user 0m5.604s sys 0m1.804s [bitmaps with pack reuse (what you get with this patch)] $ time git pack-objects --all --stdout </dev/null >/dev/null Reusing existing pack: 3237103, done. Total 3237103 (delta 0), reused 0 (delta 0) real 0m1.636s user 0m1.460s sys 0m0.172s Signed-off-by: Vicent Marti <tanoku@gmail.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-30pack-objects: split add_object_entryLibravatar Jeff King1-20/+78
This function actually does three things: 1. Check whether we've already added the object to our packing list. 2. Check whether the object meets our criteria for adding. 3. Actually add the object to our packing list. It's a little hard to see these three phases, because they happen linearly in the rather long function. Instead, this patch breaks them up into three separate helper functions. The result is a little easier to follow, though it unfortunately suffers from some optimization interdependencies between the stages (e.g., during step 3 we use the packing list index from step 1 and the packfile information from step 2). More importantly, though, the various parts can be composed differently, as they will be in the next patch. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-26do not pretend sha1write returns errorsLibravatar Jeff King1-2/+0
The sha1write function returns an int, but it will always be "0". The failure-prone parts of the function happen in the "flush" callback, which cannot pass an error back to us. So we just end up calling die() during the flush. Let's just drop the return value altogether, as it only confuses callers into thinking that it might be useful. Only one call site actually checked the return value. We can drop that check, since it just led to a die() anyway. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-05replace {pre,suf}fixcmp() with {starts,ends}_with()Libravatar Christian Couder1-1/+1
Leaving only the function definitions and declarations so that any new topic in flight can still make use of the old functions, replace existing uses of the prefixcmp() and suffixcmp() with new API functions. The change can be recreated by mechanically applying this: $ git grep -l -e prefixcmp -e suffixcmp -- \*.c | grep -v strbuf\\.c | xargs perl -pi -e ' s|!prefixcmp\(|starts_with\(|g; s|prefixcmp\(|!starts_with\(|g; s|!suffixcmp\(|ends_with\(|g; s|suffixcmp\(|!ends_with\(|g; ' on the result of preparatory changes in this series. Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-10-24pack-objects: factor out name_hashLibravatar Vicent Marti1-22/+2
As the pack-objects system grows beyond the single pack-objects.c file, more parts (like the soon-to-exist bitmap code) will need to compute hashes for matching deltas. Factor out name_hash to make it available to other files. Signed-off-by: Vicent Marti <tanoku@gmail.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-10-24pack-objects: refactor the packing listLibravatar Vicent Marti1-135/+40
The hash table that stores the packing list for a given `pack-objects` run was tightly coupled to the pack-objects code. In this commit, we refactor the hash table and the underlying storage array into a `packing_data` struct. The functionality for accessing and adding entries to the packing list is hence accessible from other parts of Git besides the `pack-objects` builtin. This refactoring is a requirement for further patches in this series that will require accessing the commit packing list from outside of `pack-objects`. The hash table implementation has been minimally altered: we now use table sizes which are always a power of two, to ensure a uniform index distribution in the array. Signed-off-by: Vicent Marti <tanoku@gmail.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-10-23Merge branch 'jc/pack-objects'Libravatar Junio C Hamano1-11/+12
* jc/pack-objects: pack-objects: shrink struct object_entry
2013-09-20Merge branch 'nd/fetch-into-shallow'Libravatar Junio C Hamano1-1/+1
When there is no sufficient overlap between old and new history during a fetch into a shallow repository, we unnecessarily sent objects the sending side knows the receiving end has. * nd/fetch-into-shallow: Add testcase for needless objects during a shallow fetch list-objects: mark more commits as edges in mark_edges_uninteresting list-objects: reduce one argument in mark_edges_uninteresting upload-pack: delegate rev walking in shallow fetch to pack-objects shallow: add setup_temporary_shallow() shallow: only add shallow graft points to new shallow file move setup_alternate_shallow and write_shallow_commits to shallow.c
2013-08-28list-objects: reduce one argument in mark_edges_uninterestingLibravatar Nguyễn Thái Ngọc Duy1-1/+1
mark_edges_uninteresting() is always called with this form mark_edges_uninteresting(revs->commits, revs, ...); Remove the first argument and let mark_edges_uninteresting figure that out by itself. It helps answer the question "are this commit list and revs related in any way?" when looking at mark_edges_uninteresting implementation. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-08-02Don't close pack fd when free'ing pack windowsLibravatar Brandon Casey1-1/+1
Now that close_one_pack() has been introduced to handle file descriptor pressure, it is not strictly necessary to close the pack file descriptor in unuse_one_window() when we're under memory pressure. Jeff King provided a justification for leaving the pack file open: If you close packfile descriptors, you can run into racy situations where somebody else is repacking and deleting packs, and they go away while you are trying to access them. If you keep a descriptor open, you're fine; they last to the end of the process. If you don't, then they disappear from under you. For normal object access, this isn't that big a deal; we just rescan the packs and retry. But if you are packing yourself (e.g., because you are a pack-objects started by upload-pack for a clone or fetch), it's much harder to recover (and we print some warnings). Let's do so (or uh, not do so). Signed-off-by: Brandon Casey <drafnel@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>