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2021-06-14Merge branch 'en/ort-perf-batch-11'Libravatar Junio C Hamano1-4/+18
Optimize out repeated rename detection in a sequence of mergy operations. * en/ort-perf-batch-11: merge-ort, diffcore-rename: employ cached renames when possible merge-ort: handle interactions of caching and rename/rename(1to1) cases merge-ort: add helper functions for using cached renames merge-ort: preserve cached renames for the appropriate side merge-ort: avoid accidental API mis-use merge-ort: add code to check for whether cached renames can be reused merge-ort: populate caches of rename detection results merge-ort: add data structures for in-memory caching of rename detection t6429: testcases for remembering renames fast-rebase: write conflict state to working tree, index, and HEAD fast-rebase: change assert() to BUG() Documentation/technical: describe remembering renames optimization t6423: rename file within directory that other side renamed
2021-05-20merge-ort, diffcore-rename: employ cached renames when possibleLibravatar Elijah Newren1-4/+18
When there are many renames between the old base of a series of commits and the new base, the way sequencer.c, merge-recursive.c, and diffcore-rename.c have traditionally split the work resulted in redetecting the same renames with each and every commit being transplanted. To address this, the last several commits have been creating a cache of rename detection results, determining when it was safe to use such a cache in subsequent merge operations, adding helper functions, and so on. See the previous half dozen commit messages for additional discussion of this optimization, particularly the message a few commits ago entitled "add code to check for whether cached renames can be reused". This commit finally ties all of that work together, modifying the merge algorithm to make use of these cached renames. For the testcases mentioned in commit 557ac0350d ("merge-ort: begin performance work; instrument with trace2_region_* calls", 2020-10-28), this change improves the performance as follows: Before After no-renames: 5.665 s ± 0.129 s 5.622 s ± 0.059 s mega-renames: 11.435 s ± 0.158 s 10.127 s ± 0.073 s just-one-mega: 494.2 ms ± 6.1 ms 500.3 ms ± 3.8 ms That's a fairly small improvement, but mostly because the previous optimizations were so effective for these particular testcases; this optimization only kicks in when the others don't. If we undid the basename-guided rename detection and skip-irrelevant-renames optimizations, then we'd see that this series by itself improved performance as follows: Before Basename Series After Just This Series no-renames: 13.815 s ± 0.062 s 5.697 s ± 0.080 s mega-renames: 1799.937 s ± 0.493 s 205.709 s ± 0.457 s Since this optimization kicks in to help accelerate cases where the previous optimizations do not apply, this last comparison shows that this cached-renames optimization has the potential to help signficantly in cases that don't meet the requirements for the other optimizations to be effective. The changes made in this optimization also lay some important groundwork for a future optimization around having collect_merge_info() avoid recursing into subtrees in more cases. However, for this optimization to be effective, merge_switch_to_result() should only be called when the rebase or cherry-pick operation has either completed or hit a case where the user needs to resolve a conflict or edit the result. If it is called after every commit, as sequencer.c does, then the working tree and index are needlessly updated with every commit and the cached metadata is tossed, defeating this optimization. Refactoring sequencer.c to only call merge_switch_to_result() at the end of the operation is a bigger undertaking, and the practical benefits of this optimization will not be realized until that work is performed. Since `test-tool fast-rebase` only updates at the end of the operation, it was used to obtain the timings above. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-04-16Merge branch 'en/ort-perf-batch-10'Libravatar Junio C Hamano1-26/+204
Various rename detection optimization to help "ort" merge strategy backend. * en/ort-perf-batch-10: diffcore-rename: determine which relevant_sources are no longer relevant merge-ort: record the reason that we want a rename for a file diffcore-rename: add computation of number of unknown renames diffcore-rename: check if we have enough renames for directories early on diffcore-rename: only compute dir_rename_count for relevant directories merge-ort: record the reason that we want a rename for a directory merge-ort, diffcore-rename: tweak dirs_removed and relevant_source type diffcore-rename: take advantage of "majority rules" to skip more renames
2021-04-08Merge branch 'en/ort-perf-batch-9'Libravatar Junio C Hamano1-11/+52
The ort merge backend has been optimized by skipping irrelevant renames. * en/ort-perf-batch-9: diffcore-rename: avoid doing basename comparisons for irrelevant sources merge-ort: skip rename detection entirely if possible merge-ort: use relevant_sources to filter possible rename sources merge-ort: precompute whether directory rename detection is needed merge-ort: introduce wrappers for alternate tree traversal merge-ort: add data structures for an alternate tree traversal merge-ort: precompute subset of sources for which we need rename detection diffcore-rename: enable filtering possible rename sources
2021-03-22Merge branch 'en/ort-perf-batch-8'Libravatar Junio C Hamano1-14/+435
Rename detection rework continues. * en/ort-perf-batch-8: diffcore-rename: compute dir_rename_guess from dir_rename_counts diffcore-rename: limit dir_rename_counts computation to relevant dirs diffcore-rename: compute dir_rename_counts in stages diffcore-rename: extend cleanup_dir_rename_info() diffcore-rename: move dir_rename_counts into dir_rename_info struct diffcore-rename: add function for clearing dir_rename_count Move computation of dir_rename_count from merge-ort to diffcore-rename diffcore-rename: add a mapping of destination names to their indices diffcore-rename: provide basic implementation of idx_possible_rename() diffcore-rename: use directory rename guided basename comparisons
2021-03-18diffcore-rename: determine which relevant_sources are no longer relevantLibravatar Elijah Newren1-1/+50
As noted a few commits ago ("diffcore-rename: only compute dir_rename_count for relevant directories"), when a source file rename is used as part of directory rename detection, we need to increment counts for each ancestor directory in dirs_removed with value RELEVANT_FOR_SELF. However, a few commits ago ("diffcore-rename: check if we have enough renames for directories early on"), we may have downgraded all relevant ancestor directories from RELEVANT_FOR_SELF to RELEVANT_FOR_ANCESTOR. For a given file, if no ancestor directory is found in dirs_removed with a value of RELEVANT_FOR_SELF, then we can downgrade relevant_source[PATH] from RELEVANT_LOCATION to RELEVANT_NO_MORE. This means we can skip detecting a rename for that particular path (and any other paths in the same directory). For the testcases mentioned in commit 557ac0350d ("merge-ort: begin performance work; instrument with trace2_region_* calls", 2020-10-28), this change improves the performance as follows: Before After no-renames: 5.680 s ± 0.096 s 5.665 s ± 0.129 s mega-renames: 13.812 s ± 0.162 s 11.435 s ± 0.158 s just-one-mega: 506.0 ms ± 3.9 ms 494.2 ms ± 6.1 ms While this improvement looks rather modest for these testcases (because all the previous optimizations were sufficient to nearly remove all time spent in rename detection already), consider this alternative testcase tweaked from the ones in commit 557ac0350d as follows <Same initial setup as commit 557ac0350d, then...> $ git switch -c add-empty-file v5.5 $ >drivers/gpu/drm/i915/new-empty-file $ git add drivers/gpu/drm/i915/new-empty-file $ git commit -m "new file" $ git switch 5.4-rename $ git cherry-pick --strategy=ort add-empty-file For this testcase, we see the following improvement: Before After pick-empty: 1.936 s ± 0.024 s 688.1 ms ± 4.2 ms So roughly a factor of 3 speedup. At $DAYJOB, there was a particular repository and cherry-pick that inspired this optimization; for that case I saw a speedup factor of 7 with this optimization. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-18diffcore-rename: add computation of number of unknown renamesLibravatar Elijah Newren1-4/+37
The previous commit can only be effective if we have a computation of the number of paths under a given directory which are still have pending renames, and expected this number to be recorded in the dir_rename_count map under the key UNKNOWN_DIR. Add the code necessary to compute these values. Note that this change means dir_rename_count might have a directory whose only entry (for UNKNOWN_DIR) was removed by the time merge-ort goes to check it. To account for this, merge-ort needs to check for the case where the max count is 0. With this change we are now computing the necessary value for each directory in dirs_removed, but are not using that value anywhere. The next two commits will make use of the values stored in dirs_removed in order to compute whether each relevant_source (that is needed only for directory rename detection) has become unnecessary. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-18diffcore-rename: check if we have enough renames for directories early onLibravatar Elijah Newren1-10/+63
As noted in the past few commits, if we can determine that a directory already has enough renames to determine how directory rename detection will be decided for that directory, then we can mark that directory as no longer needing any more renames detected for files underneath it. For such directories, we change the value in the dirs_removed map from RELEVANT_TO_SELF to RELEVANT_FOR_ANCESTOR. A subsequent patch will use this information while iterating over the remaining potential rename sources to mark ones that were only location_relevant as unneeded if no containing directory is still marked as RELEVANT_TO_SELF. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-18diffcore-rename: only compute dir_rename_count for relevant directoriesLibravatar Elijah Newren1-5/+22
When one side adds files to a directory that the other side renamed, directory rename detection is used to either move the new paths to the newer directory or warn the user about the fact that another path location might be better. If a parent of the given directory had new files added to it, any renames in the current directory are also part of determining where the parent directory is renamed to. Thus, naively, we need to record each rename N times for a path at depth N. However, we can use the additional information added to dirs_removed in the last commit to avoid traversing all N parent directories in many cases. Let's use an example to explain how this works. If we have a path named src/old_dir/a/b/file.c and src/old_dir doesn't exist on one side of history, but the other added a file named src/old_dir/newfile.c, then if one side renamed src/old_dir/a/b/file.c => source/new_dir/a/b/file.c then this file would affect potential directory rename detection counts for src/old_dir/a/b => source/new_dir/a/b src/old_dir/a => source/new_dir/a src/old_dir => source/new_dir src => source adding a weight of 1 to each in dir_rename_counts. However, if src/ exists on both sides of history, then we don't need to track any entries for it in dir_rename_counts. That was implemented previously. What we are adding now, is that if no new files were added to src/old_dir/a or src/old_dir/b, then we don't need to have counts in dir_rename_count for those directories either. In short, we only need to track counts in dir_rename_count for directories whose dirs_removed value is RELEVANT_FOR_SELF. And as soon as we reach a directory that isn't in dirs_removed (signalled by returning the default value of NOT_RELEVANT from strintmap_get()), we can stop looking any further up the directory hierarchy. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-18merge-ort: record the reason that we want a rename for a directoryLibravatar Elijah Newren1-1/+1
When one side of history renames a directory, and the other side of history added files to the old directory, directory rename detection is used to warn about the location of the added files so the user can move them to the old directory or keep them with the new one. This sets up three different types of directories: * directories that had new files added to them * directories underneath a directory that had new files added to them * directories where no new files were added to it or any leading path Save this information in dirs_removed; the next several commits will make use of this information. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-18merge-ort, diffcore-rename: tweak dirs_removed and relevant_source typeLibravatar Elijah Newren1-23/+24
As noted in the previous commit, we want to be able to take advantage of the "majority rules" portion of directory rename detection to avoid detecting more renames than necessary. However, for diffcore-rename to take advantage of that, it needs to know whether a rename source file was needed for just directory rename detection reasons, or if it is wanted for potential three-way content merging. Modify relevant_sources from a strset to a strintmap, so we can encode additional information. We also modify dirs_removed from a strset to a strintmap at the same time because trying to determine what files are needed for directory rename detection will require us tracking a bit more information for each directory. This commit only changes the types of the two variables from strset to strintmap; it does not actually store any special values yet and for now only checks for presence of entries in the strintmap. Thus, the code is functionally identical to how it behaved before. Future commits will start associating values with each key for these two maps. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-18diffcore-rename: take advantage of "majority rules" to skip more renamesLibravatar Elijah Newren1-0/+25
In directory rename detection (when a directory is removed on one side of history and the other side adds new files to that directory), we work to find where the greatest number of files within that directory were renamed to so that the new files can be moved with the majority of the files. Naively, we can just do this by detecting renames for *all* files within the removed/renamed directory, looking at all the destination directories where files within that directory were moved, and if there is more than one such directory then taking the one with the greatest number of files as the directory where the old directory was renamed to. However, sometimes there are enough renames from exact rename detection or basename-guided rename detection that we have enough information to determine the majority winner already. Add a function meant to compute whether particular renames are still needed based on this majority rules check. The next several commits will then add the necessary infrastructure to get the information we need to compute which additional rename sources we can skip. An important side note for future further optimization: There is a possible improvement to this optimization that I have not yet attempted and will not be included in this series of patches: we could first check whether exact renames provide enough information for us to determine directory renames, and avoid doing basename-guided rename detection on some or all of the RELEVANT_LOCATION files within those directories. In effect, this variant would mean doing the handle_early_known_dir_renames() both after exact rename detection and again after basename-guided rename detection, though it would also mean decrementing the number of "unknown" renames for each rename we found from basename-guided rename detection. Adding this additional check for skippable renames right after exact rename detection might turn out to be valuable, especially for partial clones where it might allow us to download certain source files entirely. However, this particular optimization was actually the last one I did in original implementation order, and by the time I implemented this idea, every testcase I had was sufficiently fast that further optimization was unwarranted. If future testcases arise that tax rename detection more heavily (or perhaps partial clones can benefit from avoiding loading more objects), it may be worth implementing this more involved variant. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-13use CALLOC_ARRAYLibravatar René Scharfe1-2/+1
Add and apply a semantic patch for converting code that open-codes CALLOC_ARRAY to use it instead. It shortens the code and infers the element size automatically. Signed-off-by: René Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-10diffcore-rename: avoid doing basename comparisons for irrelevant sourcesLibravatar Elijah Newren1-4/+33
The basename comparison optimization implemented in find_basename_matches() is very beneficial since it allows a source to sometimes only be compared with one other file instead of N other files. When a match is found, both a source and destination can be removed from the matrix of inexact rename comparisons. In contrast, the irrelevant source optimization only allows us to remove a source from the matrix of inexact rename comparisons...but it has the advantage of allowing a source file to not even be loaded into memory at all and be compared to 0 other files. Generally, not even comparing is a bigger performance win, so when both optimizations could apply, prefer to use the irrelevant-source optimization. For the testcases mentioned in commit 557ac0350d ("merge-ort: begin performance work; instrument with trace2_region_* calls", 2020-10-28), this change improves the performance as follows: Before After no-renames: 5.708 s ± 0.111 s 5.680 s ± 0.096 s mega-renames: 102.171 s ± 0.440 s 13.812 s ± 0.162 s just-one-mega: 3.471 s ± 0.015 s 506.0 ms ± 3.9 ms Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-10diffcore-rename: enable filtering possible rename sourcesLibravatar Elijah Newren1-7/+19
Add the ability to diffcore_rename_extended() to allow external callers to declare that they only need renames detected for a subset of source files, and use that information to skip detecting renames for them. There are two important pieces to this optimization that may not be obvious at first glance: * We do not require callers to just filter the filepairs out to remove the non-relevant sources, because exact rename detection is fast and when it finds a match it can remove both a source and a destination whereas the relevant_sources filter can only remove a source. * We need to filter out the source pairs in a preliminary pass instead of adding a strset_contains(relevant_sources, one->path) check within the nested matrix loop. The reason for that is if we have 30k renames, doing 30k * 30k = 900M strset_contains() calls becomes extraordinarily expensive and defeats the performance gains from this change; we only want to do 30k such calls instead. If callers pass NULL for relevant_sources, that is special cases to treat all sources as relevant. Since all callers currently pass NULL, this optimization does not yet have any effect. Subsequent commits will have merge-ort compute a set of relevant_sources to restrict which sources we detect renames for, and have merge-ort pass that set of relevant_sources to diffcore_rename_extended(). A note about filtering order: Some may be curious why we don't filter out irrelevant sources at the same time we filter out exact renames. While that technically could be done at this point, there are two reasons to defer it: First, was to reinforce a lesson that was too easy to forget. As I mentioned above, in the past I filtered irrelevant sources out before exact rename checking, and then discovered that exact renames' ability to remove both sources and destinations was an important consideration and thus doing the filtering after exact rename checking would speed things up. Then at some point I realized that basename matching could also remove both sources and destinations, and decided to put irrelevant source filtering after basename filtering. That slowed things down a lot. But, despite learning about this important ordering, in later restructuring I forgot and made the same mistake of putting the filtering after basename guided rename detection again. So, I have this series of patches structured to do the irrelevant filtering last to start to show how much extra it costs, and then add relevant filtering in to find_basename_matches() to show how much it speeds things up. Basically, it's a way to reinforce something that apparently was too easy to forget, and make sure the commit messages record this lesson. Second, the items in the "relevant_sources" in this patch series will include all sources that *might be* relevant. It has to be conservative and catch anything that might need a rename, but in the patch series after this one we'll find ways to weed out more of the *might be* relevant ones. Unfortunately, merge-ort does not have sufficient information to weed those ones out, and there isn't enough information at the time of filtering exact renames out to remove the extra ones either. It has to be deferred. So the deferral is in part to simplify some later additions. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-26diffcore-rename: compute dir_rename_guess from dir_rename_countsLibravatar Elijah Newren1-4/+41
dir_rename_counts has a mapping of a mapping, in particular, it has old_dir => { new_dir => count } We want a simple mapping of old_dir => new_dir based on which new_dir had the highest count for a given old_dir. Compute this and store it in dir_rename_guess. This is the final piece of the puzzle needed to make our guesses at which directory files have been moved to when basenames aren't unique. For the testcases mentioned in commit 557ac0350d ("merge-ort: begin performance work; instrument with trace2_region_* calls", 2020-10-28), this change improves the performance as follows: Before After no-renames: 12.775 s ± 0.062 s 12.596 s ± 0.061 s mega-renames: 188.754 s ± 0.284 s 130.465 s ± 0.259 s just-one-mega: 5.599 s ± 0.019 s 3.958 s ± 0.010 s Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-26diffcore-rename: limit dir_rename_counts computation to relevant dirsLibravatar Elijah Newren1-0/+10
We are using dir_rename_counts to count the number of other directories that files within a directory moved to. We only need this information for directories that disappeared, though, so we can return early from update_dir_rename_counts() for other paths. If dirs_removed is passed to diffcore_rename_extended(), then it provides the relevant bits of information for us to limit this counting to relevant dirs. If dirs_removed is not passed, we would need to compute some replacement in order to do this limiting. Introduce a new info->relevant_source_dirs variable for this purpose, even though at this stage we will only set it to dirs_removed for simplicity. Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-26diffcore-rename: compute dir_rename_counts in stagesLibravatar Elijah Newren1-40/+70
Compute dir_rename_counts based just on exact renames to start, as that can provide us useful information in find_basename_matches(). This is done by moving the code from compute_dir_rename_counts() into initialize_dir_rename_info(), resulting in it being computed earlier and based just on exact renames. Since that's an incomplete result, we augment the counts via calling update_dir_rename_counts() after each basename-guide and inexact rename detection match is found. Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-26diffcore-rename: extend cleanup_dir_rename_info()Libravatar Elijah Newren1-4/+36
When diffcore_rename_extended() is passed a NULL dir_rename_count, we will still want to create a temporary one for use by find_basename_matches(), but have it fully deallocated before diffcore_rename_extended() returns. However, when diffcore_rename_extended() is passed a dir_rename_count, we want to fill that strmap with appropriate values and return it. However, for our interim purposes we may also add entries corresponding to directories that cannot have been renamed due to still existing on both sides. Extend cleanup_dir_rename_info() to handle these two different cases, cleaning up the relevant bits of information for each case. Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-26diffcore-rename: move dir_rename_counts into dir_rename_info structLibravatar Elijah Newren1-11/+16
This continues the migration of the directory rename detection code into diffcore-rename, now taking the simple step of combining it with the dir_rename_info struct. Future commits will then make dir_rename_counts be computed in stages, and add computation of dir_rename_guess. Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-26diffcore-rename: add function for clearing dir_rename_countLibravatar Elijah Newren1-0/+12
As we adjust the usage of dir_rename_count we want to have a function for clearing, or partially clearing it out. Add a partial_clear_dir_rename_count() function for this purpose. Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-26Move computation of dir_rename_count from merge-ort to diffcore-renameLibravatar Elijah Newren1-1/+137
Move the computation of dir_rename_count from merge-ort.c to diffcore-rename.c, making slight adjustments to the data structures based on the move. While the diffstat looks large, viewing this commit with --color-moved makes it clear that only about 20 lines changed. With this patch, the computation of dir_rename_count is still only done after inexact rename detection, but subsequent commits will add a preliminary computation of dir_rename_count after exact rename detection, followed by some updates after inexact rename detection. Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-26diffcore-rename: add a mapping of destination names to their indicesLibravatar Elijah Newren1-0/+45
Compute a mapping of full filename to the index within rename_dst where that filename is found, and store it in idx_map. idx_possible_rename() needs this to quickly finding an array entry in rename_dst given the pathname. While at it, add placeholder initializations for dir_rename_count and dir_rename_guess; these will be more fully populated in subsequent commits. Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-26diffcore-rename: provide basic implementation of idx_possible_rename()Libravatar Elijah Newren1-6/+94
Add a new struct dir_rename_info with various values we need inside our idx_possible_rename() function introduced in the previous commit. Add a basic implementation for this function showing how we plan to use the variables, but which will just return early with a value of -1 (not found) when those variables are not set up. Future commits will do the work necessary to set up those other variables so that idx_possible_rename() does not always return -1. Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-26diffcore-rename: use directory rename guided basename comparisonsLibravatar Elijah Newren1-8/+34
A previous commit noted that it is very common for people to move files across directories while keeping their filename the same. The last few commits took advantage of this and showed that we can accelerate rename detection significantly using basenames; since files with the same basename serve as likely rename candidates, we can check those first and remove them from the rename candidate pool if they are sufficiently similar. Unfortunately, the previous optimization was limited by the fact that the remaining basenames after exact rename detection are not always unique. Many repositories have hundreds of build files with the same name (e.g. Makefile, .gitignore, build.gradle, etc.), and may even have hundreds of source files with the same name. (For example, the linux kernel has 100 setup.c, 87 irq.c, and 112 core.c files. A repository at $DAYJOB has a lot of ObjectFactory.java and Plugin.java files). For these files with non-unique basenames, we are faced with the task of attempting to determine or guess which directory they may have been relocated to. Such a task is precisely the job of directory rename detection. However, there are two catches: (1) the directory rename detection code has traditionally been part of the merge machinery rather than diffcore-rename.c, and (2) directory rename detection currently runs after regular rename detection is complete. The 1st catch is just an implementation issue that can be overcome by some code shuffling. The 2nd requires us to add a further approximation: we only have access to exact renames at this point, so we need to do directory rename detection based on just exact renames. In some cases we won't have exact renames, in which case this extra optimization won't apply. We also choose to not apply the optimization unless we know that the underlying directory was removed, which will require extra data to be passed in to diffcore_rename_extended(). Also, even if we get a prediction about which directory a file may have relocated to, we will still need to check to see if there is a file in the predicted directory, and then compare the two files to see if they meet the higher min_basename_score threshold required for marking the two files as renames. This commit introduces an idx_possible_rename() function which will do this directory rename detection for us and give us the index within rename_dst of the resulting filename. For now, this function is hardcoded to return -1 (not found) and just hooks up how its results would be used once we have a more complete implementation in place. Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-15diffcore-rename: guide inexact rename detection based on basenamesLibravatar Elijah Newren1-5/+48
Make use of the new find_basename_matches() function added in the last two patches, to find renames more rapidly in cases where we can match up files based on basenames. As a quick reminder (see the last two commit messages for more details), this means for example that docs/extensions.txt and docs/config/extensions.txt are considered likely renames if there are no remaining 'extensions.txt' files elsewhere among the added and deleted files, and if a similarity check confirms they are similar, then they are marked as a rename without looking for a better similarity match among other files. This is a behavioral change, as covered in more detail in the previous commit message. We do not use this heuristic together with either break or copy detection. The point of break detection is to say that filename similarity does not imply file content similarity, and we only want to know about file content similarity. The point of copy detection is to use more resources to check for additional similarities, while this is an optimization that uses far less resources but which might also result in finding slightly fewer similarities. So the idea behind this optimization goes against both of those features, and will be turned off for both. For the testcases mentioned in commit 557ac0350d ("merge-ort: begin performance work; instrument with trace2_region_* calls", 2020-10-28), this change improves the performance as follows: Before After no-renames: 13.815 s ± 0.062 s 13.294 s ± 0.103 s mega-renames: 1799.937 s ± 0.493 s 187.248 s ± 0.882 s just-one-mega: 51.289 s ± 0.019 s 5.557 s ± 0.017 s Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-15diffcore-rename: complete find_basename_matches()Libravatar Elijah Newren1-3/+79
It is not uncommon in real world repositories for the majority of file renames to not change the basename of the file; i.e. most "renames" are just a move of files into different directories. We can make use of this to avoid comparing all rename source candidates with all rename destination candidates, by first comparing sources to destinations with the same basenames. If two files with the same basename are sufficiently similar, we record the rename; if not, we include those files in the more exhaustive matrix comparison. This means we are adding a set of preliminary additional comparisons, but for each file we only compare it with at most one other file. For example, if there was a include/media/device.h that was deleted and a src/module/media/device.h that was added, and there are no other device.h files in the remaining sets of added and deleted files after exact rename detection, then these two files would be compared in the preliminary step. This commit does not yet actually employ this new optimization, it merely adds a function which can be used for this purpose. The next commit will do the necessary plumbing to make use of it. Note that this optimization might give us different results than without the optimization, because it's possible that despite files with the same basename being sufficiently similar to be considered a rename, there's an even better match between files without the same basename. I think that is okay for four reasons: (1) it's easy to explain to the users what happened if it does ever occur (or even for them to intuitively figure out), (2) as the next patch will show it provides such a large performance boost that it's worth the tradeoff, and (3) it's somewhat unlikely that despite having unique matching basenames that other files serve as better matches. Reason (4) takes a full paragraph to explain... If the previous three reasons aren't enough, consider what rename detection already does. Break detection is not the default, meaning that if files have the same _fullname_, then they are considered related even if they are 0% similar. In fact, in such a case, we don't even bother comparing the files to see if they are similar let alone comparing them to all other files to see what they are most similar to. Basically, we override content similarity based on sufficient filename similarity. Without the filename similarity (currently implemented as an exact match of filename), we swing the pendulum the opposite direction and say that filename similarity is irrelevant and compare a full N x M matrix of sources and destinations to find out which have the most similar contents. This optimization just adds another form of filename similarity comparison, but augments it with a file content similarity check as well. Basically, if two files have the same basename and are sufficiently similar to be considered a rename, mark them as such without comparing the two to all other rename candidates. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-15diffcore-rename: compute basenames of source and dest candidatesLibravatar Elijah Newren1-0/+63
We want to make use of unique basenames among remaining source and destination files to help inform rename detection, so that more likely pairings can be checked first. (src/moduleA/foo.txt and source/module/A/foo.txt are likely related if there are no other 'foo.txt' files among the remaining deleted and added files.) Add a new function, not yet used, which creates a map of the unique basenames within rename_src and another within rename_dst, together with the indices within rename_src/rename_dst where those basenames show up. Non-unique basenames still show up in the map, but have an invalid index (-1). This function was inspired by the fact that in real world repositories, files are often moved across directories without changing names. Here are some sample repositories and the percentage of their historical renames (as of early 2020) that preserved basenames: * linux: 76% * gcc: 64% * gecko: 79% * webkit: 89% These statistics alone don't prove that an optimization in this area will help or how much it will help, since there are also unpaired adds and deletes, restrictions on which basenames we consider, etc., but it certainly motivated the idea to try something in this area. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-15diffcore-rename: filter rename_src list when possibleLibravatar Elijah Newren1-8/+51
We have to look at each entry in rename_src a total of rename_dst_nr times. When we're not detecting copies, any exact renames or ignorable rename paths will just be skipped over. While checking that these can be skipped over is a relatively cheap check, it's still a waste of time to do that check more than once, let alone rename_dst_nr times. When rename_src_nr is a few thousand times bigger than the number of relevant sources (such as when cherry-picking a commit that only touched a handful of files, but from a side of history that has different names for some high level directories), this time can add up. First make an initial pass over the rename_src array and move all the relevant entries to the front, so that we can iterate over just those relevant entries. For the testcases mentioned in commit 557ac0350d ("merge-ort: begin performance work; instrument with trace2_region_* calls", 2020-10-28), this change improves the performance as follows: Before After no-renames: 14.119 s ± 0.101 s 13.815 s ± 0.062 s mega-renames: 1802.044 s ± 0.828 s 1799.937 s ± 0.493 s just-one-mega: 51.391 s ± 0.028 s 51.289 s ± 0.019 s Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-02-12diffcore-rename: no point trying to find a match better than exactLibravatar Elijah Newren1-6/+14
diffcore_rename() had some code to avoid having destination paths that already had an exact rename detected from being re-checked for other renames. Source paths, however, were re-checked because we wanted to allow the possibility of detecting copies. But if copy detection isn't turned on, then this merely amounts to attempting to find a better-than-exact match, which naturally ends up being an expensive no-op. In particular, copy detection is never turned on by the merge machinery. For the testcases mentioned in commit 557ac0350d ("merge-ort: begin performance work; instrument with trace2_region_* calls", 2020-10-28), this change improves the performance as follows: Before After no-renames: 14.263 s ± 0.053 s 14.119 s ± 0.101 s mega-renames: 5504.231 s ± 5.150 s 1802.044 s ± 0.828 s just-one-mega: 158.534 s ± 0.498 s 51.391 s ± 0.028 s Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-01-23merge-ort: begin performance work; instrument with trace2_region_* callsLibravatar Elijah Newren1-0/+8
Add some timing instrumentation for both merge-ort and diffcore-rename; I used these to measure and optimize performance in both, and several future patch series will build on these to reduce the timings of some select testcases. === Setup === The primary testcase I used involved rebasing a random topic in the linux kernel (consisting of 35 patches) against an older version. I added two variants, one where I rename a toplevel directory, and another where I only rebase one patch instead of the whole topic. The setup is as follows: $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git $ git branch hwmon-updates fd8bdb23b91876ac1e624337bb88dc1dcc21d67e $ git branch hwmon-just-one fd8bdb23b91876ac1e624337bb88dc1dcc21d67e~34 $ git branch base 4703d9119972bf586d2cca76ec6438f819ffa30e $ git switch -c 5.4-renames v5.4 $ git mv drivers pilots # Introduce over 26,000 renames $ git commit -m "Rename drivers/ to pilots/" $ git config merge.renameLimit 30000 $ git config merge.directoryRenames true === Testcases === Now with REBASE standing for either "git rebase [--merge]" (using merge-recursive) or "test-tool fast-rebase" (using merge-ort), the testcases are: Testcase #1: no-renames $ git checkout v5.4^0 $ REBASE --onto HEAD base hwmon-updates Note: technically the name is misleading; there are some renames, but very few. Rename detection only takes about half the overall time. Testcase #2: mega-renames $ git checkout 5.4-renames^0 $ REBASE --onto HEAD base hwmon-updates Testcase #3: just-one-mega $ git checkout 5.4-renames^0 $ REBASE --onto HEAD base hwmon-just-one === Timing results === Overall timings, using hyperfine (1 warmup run, 3 runs for mega-renames, 10 runs for the other two cases): merge-recursive merge-ort no-renames: 18.912 s ± 0.174 s 14.263 s ± 0.053 s mega-renames: 5964.031 s ± 10.459 s 5504.231 s ± 5.150 s just-one-mega: 149.583 s ± 0.751 s 158.534 s ± 0.498 s A single re-run of each with some breakdowns: --- no-renames --- merge-recursive merge-ort overall runtime: 19.302 s 14.257 s inexact rename detection: 7.603 s 7.906 s everything else: 11.699 s 6.351 s --- mega-renames --- merge-recursive merge-ort overall runtime: 5950.195 s 5499.672 s inexact rename detection: 5746.309 s 5487.120 s everything else: 203.886 s 17.552 s --- just-one-mega --- merge-recursive merge-ort overall runtime: 151.001 s 158.582 s inexact rename detection: 143.448 s 157.835 s everything else: 7.553 s 0.747 s === Timing observations === 0) Maximum speedup The "everything else" row represents the maximum speedup we could achieve if we were to somehow infinitely parallelize inexact rename detection, but leave everything else alone. The fact that this is so much smaller than the real runtime (even in the case with virtually no renames) makes it clear just how overwhelmingly large the time spent on rename detection can be. 1) no-renames 1a) merge-ort is faster than merge-recursive, which is nice. However, this still should not be considered good enough. Although the "merge" backend to rebase (merge-recursive) is sometimes faster than the "apply" backend, this is one of those cases where it is not. In fact, even merge-ort is slower. The "apply" backend can complete this testcase in 6.940 s ± 0.485 s which is about 2x faster than merge-ort and 3x faster than merge-recursive. One goal of the merge-ort performance work will be to make it faster than git-am on this (and similar) testcases. 2) mega-renames 2a) Obviously rename detection is a huge cost; it's where most the time is spent. We need to cut that down. If we could somehow infinitely parallelize it and drive its time to 0, the merge-recursive time would drop to about 204s, and the merge-ort time would drop to about 17s. I think this particular stat shows I've subtly baked a couple performance improvements into merge-ort and into fast-rebase already. 3) just-one-mega 3a) not much to say here, it just gives some flavor for how rebasing only one patch compares to rebasing 35. === Goals === This patch is obviously just the beginning. Here are some of my goals that this measurement will help us achieve: * Drive the cost of rename detection down considerably for merges * After the above has been achieved, see if there are other slowness factors (which would have previously been overshadowed by rename detection costs) which we can then focus on and also optimize. * Ensure our rebase testcase that requires little rename detection is noticeably faster with merge-ort than with apply-based rebase. Signed-off-by: Elijah Newren <newren@gmail.com> Acked-by: Taylor Blau <ttaylorr@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-01-04diffcore-rename: remove unnecessary duplicate entry checksLibravatar Elijah Newren1-23/+0
Commit 25d5ea410f ("[PATCH] Redo rename/copy detection logic.", 2005-05-24) added a duplicate entry check on rename_src in order to avoid segfaults; the code at the time was prone to double free()s and an easy way to avoid it was just to turn off rename detection for any duplicate entries. Note that the form of the check was modified two commits ago in this series. Similarly, commit 4d6be03b95 ("diffcore-rename: avoid processing duplicate destinations", 2015-02-26) added a duplicate entry check on rename_dst for the exact same reason -- the code was prone to double free()s, and an easy way to avoid it was just to turn off rename detection entirely. Note that the form of the check was modified in the commit just before this one. In the original code in both places, the code was dealing with individual diff_filespecs and trying to match things up, instead of just keeping the original diff_filepairs around as we do now. The intervening change in structure has fixed the accounting problems and the associated double free()s that used to occur, and thus we already have a better fix. As such, we can remove the band-aid checks for duplicate entries. Due to the last two patches, the diffcore_rename() setup is no longer a sizeable chunk of overall runtime. Thus, in a large rebase of many commits with lots of renames and several optimizations to inexact rename detection, this patch only speeds up the overall code by about half a percent or so and is pretty close to the run-to-run variability making it hard to get an exact measurement. However, with some trace2 regions around the setup code in diffcore_rename() so that I can focus on just it, I measure that this patch consistently saves almost a third of the remaining time spent in diffcore_rename() setup. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-14diffcore-rename: accelerate rename_dst setupLibravatar Elijah Newren1-83/+65
register_rename_src() simply references the passed pair inside rename_src. In contrast, add_rename_dst() did something entirely different for rename_dst. Instead of copying the passed pair, it made a copy of the second diff_filespec from the passed pair, referenced it, and then set the diff_rename_dst.pair field to NULL. Later, when a pairing is found, record_rename_pair() allocated a full diff_filepair via diff_queue() and pointed its src and dst fields at the appropriate diff_filespecs. This contrast between register_rename_src() for the rename_src data structure and add_rename_dst() for the rename_dst data structure is oddly inconsistent and requires more memory and work than necessary. Let's just reference the original diff_filepair in rename_dst as-is, just as we do with rename_src. Add a new rename_dst.is_rename field, since the rename_dst.p field is never NULL unlike the old rename_dst.pair field. Taking advantage of this change and the fact that same-named paths will be adjacent, we can get rid of the sorting of the array and most of the lookups on it, allowing us to instead just append as we go. However, there is one remaining reason to still keep locate_rename_dst(): handling broken pairs (i.e. when break detection is on). Those are somewhat rare, but we can set up a simple strintmap to get the map between the source and the index. Doing that allows us to still have a fast lookup without sorting the rename_dst array. Since the sorting had been done in a weakly quadratic manner, when many renames are involved this time could add up. There is still a strcmp() in add_rename_dst() that I have left in place to make it easier to verify that the algorithm has the same results. This strcmp() is there to check for duplicate destination entries (which was the easiest way at the time to avoid segfaults in the diffcore-rename code when trees had multiple entries at a given path). The underlying double free()s are no longer an issue with the new algorithm, but that can be addressed in a subsequent commit. This patch is being submitted in a different order than its original development, but in a large rebase of many commits with lots of renames and with several optimizations to inexact rename detection, both setup time and write back to output queue time from diffcore_rename() were sizeable chunks of overall runtime. This patch accelerated the setup time by about 65%, and final write back to the output queue time by about 50%, resulting in an overall drop of 3.5% on the execution time of rebasing a few dozen patches. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-14diffcore-rename: simplify and accelerate register_rename_src()Libravatar Elijah Newren1-26/+13
register_rename_src() took pains to create an array in rename_src which was sorted by pathname of the contained diff_filepair. The sorting was entirely unnecessary since callers pass filepairs to us in sorted order. We can simply append to the end of the rename_src array, speeding up diffcore_rename() setup time. Also, note that I dropped the return type on the function since it was unconditionally discarded anyway. This patch is being submitted in a different order than its original development, but in a large rebase of many commits with lots of renames and with several optimizations to inexact rename detection, diffcore_rename() setup time was a sizeable chunk of overall runtime. This patch dropped execution time of rebasing 35 commits with lots of renames by 2% overall. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-14diffcore-rename: reduce jumpiness in progress countersLibravatar Elijah Newren1-2/+3
Inexact rename detection works by comparing all sources to all destinations, computing similarities, and then finding the best matches among those that are sufficiently similar. However, it is preceded by exact rename detection that works by checking if there are files with identical hashes. If exact renames are found, we can exclude some files from inexact rename detection. The inexact rename detection loops over the full set of files, but immediately skips those for which rename_dst[i].is_rename is true and thus doesn't compare any sources to that destination. As such, these paths shouldn't be included in the progress counter. For the eagle eyed, this change hints at an actual optimization -- the first one I presented at Git Merge 2020. I'll be submitting that optimization later, once the basic merge-ort algorithm has merged. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-14diffcore-rename: simplify limit checkLibravatar Elijah Newren1-6/+9
diffcore-rename had two different checks of the form if ((a < limit || b < limit) && a * b <= limit * limit) This can be simplified to if (st_mult(a, b) <= st_mult(limit, limit)) which makes it clearer how we are checking for overflow, and makes it much easier to parse given the drop from 8 to 4 variable appearances. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-14diffcore-rename: avoid usage of global in too_many_rename_candidates()Libravatar Elijah Newren1-12/+12
too_many_rename_candidates() got the number of rename destinations via an argument to the function, but the number of rename sources via a global variable. That felt rather inconsistent. Pass in the number of rename sources as an argument as well. While we are at it... We had a local variable, num_src, that served two purposes. Initially it was set to the global value, but later was used for counting a subset of the number of sources. Since we now have a function argument for the former usage, introduce a clearer variable name for the latter usage. This patch has no behavioral changes; it's just renaming and passing an argument instead of grabbing it from the global namespace. (You may find it easier to view the patch using git diff's --color-words option.) Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-14diffcore-rename: rename num_create to num_destinationsLibravatar Elijah Newren1-12/+13
Our main data structures are rename_src and rename_dst. For counters of these data structures, num_sources and num_destinations seem natural; definitely more so than using num_create for the latter. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-11-02hashmap: provide deallocation function namesLibravatar Elijah Newren1-1/+1
hashmap_free(), hashmap_free_entries(), and hashmap_free_() have existed for a while, but aren't necessarily the clearest names, especially with hashmap_partial_clear() being added to the mix and lazy-initialization now being supported. Peff suggested we adopt the following names[1]: - hashmap_clear() - remove all entries and de-allocate any hashmap-specific data, but be ready for reuse - hashmap_clear_and_free() - ditto, but free the entries themselves - hashmap_partial_clear() - remove all entries but don't deallocate table - hashmap_partial_clear_and_free() - ditto, but free the entries This patch provides the new names and converts all existing callers over to the new naming scheme. [1] https://lore.kernel.org/git/20201030125059.GA3277724@coredump.intra.peff.net/ Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-04-07diff: restrict when prefetching occursLibravatar Jonathan Tan1-4/+51
Commit 7fbbcb21b1 ("diff: batch fetching of missing blobs", 2019-04-08) optimized "diff" by prefetching blobs in a partial clone, but there are some cases wherein blobs do not need to be prefetched. In these cases, any command that uses the diff machinery will unnecessarily fetch blobs. diffcore_std() may read blobs when it calls the following functions: (1) diffcore_skip_stat_unmatch() (controlled by the config variable diff.autorefreshindex) (2) diffcore_break() and diffcore_merge_broken() (for break-rewrite detection) (3) diffcore_rename() (for rename detection) (4) diffcore_pickaxe() (for detecting addition/deletion of specified string) Instead of always prefetching blobs, teach diffcore_skip_stat_unmatch(), diffcore_break(), and diffcore_rename() to prefetch blobs upon the first read of a missing object. This covers (1), (2), and (3): to cover the rest, teach diffcore_std() to prefetch if the output type is one that includes blob data (and hence blob data will be required later anyway), or if it knows that (4) will be run. Helped-by: Jeff King <peff@peff.net> Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-04-07diff: make diff_populate_filespec_options structLibravatar Jonathan Tan1-5/+8
The behavior of diff_populate_filespec() currently can be customized through a bitflag, but a subsequent patch requires it to support a non-boolean option. Replace the bitflag with an options struct. Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-01-31sha1-file: pass git_hash_algo to hash_object_file()Libravatar Matheus Tavares1-2/+2
Allow hash_object_file() to work on arbitrary repos by introducing a git_hash_algo parameter. Change callers which have a struct repository pointer in their scope to pass on the git_hash_algo from the said repo. For all other callers, pass on the_hash_algo, which was already being used internally at hash_object_file(). This functionality will be used in the following patch to make check_object_signature() be able to work on arbitrary repos (which, in turn, will be used to fix an inconsistency at object.c:parse_object()). Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-15Merge branch 'ew/hashmap'Libravatar Junio C Hamano1-8/+7
Code clean-up of the hashmap API, both users and implementation. * ew/hashmap: hashmap_entry: remove first member requirement from docs hashmap: remove type arg from hashmap_{get,put,remove}_entry OFFSETOF_VAR macro to simplify hashmap iterators hashmap: introduce hashmap_free_entries hashmap: hashmap_{put,remove} return hashmap_entry * hashmap: use *_entry APIs for iteration hashmap_cmp_fn takes hashmap_entry params hashmap_get{,_from_hash} return "struct hashmap_entry *" hashmap: use *_entry APIs to wrap container_of hashmap_get_next returns "struct hashmap_entry *" introduce container_of macro hashmap_put takes "struct hashmap_entry *" hashmap_remove takes "const struct hashmap_entry *" hashmap_get takes "const struct hashmap_entry *" hashmap_add takes "struct hashmap_entry *" hashmap_get_next takes "const struct hashmap_entry *" hashmap_entry_init takes "struct hashmap_entry *" packfile: use hashmap_entry in delta_base_cache_entry coccicheck: detect hashmap_entry.hash assignment diff: use hashmap_entry_init on moved_entry.ent
2019-10-07OFFSETOF_VAR macro to simplify hashmap iteratorsLibravatar Eric Wong1-1/+1
While we cannot rely on a `__typeof__' operator being portable to use with `offsetof'; we can calculate the pointer offset using an existing pointer and the address of a member using pointer arithmetic for compilers without `__typeof__'. This allows us to simplify usage of hashmap iterator macros by not having to specify a type when a pointer of that type is already given. In the future, list iterator macros (e.g. list_for_each_entry) may also be implemented using OFFSETOF_VAR to save hackers the trouble of using container_of/list_entry macros and without relying on non-portable `__typeof__'. v3: use `__typeof__' to avoid clang warnings Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap: introduce hashmap_free_entriesLibravatar Eric Wong1-1/+1
`hashmap_free_entries' behaves like `container_of' and passes the offset of the hashmap_entry struct to the internal `hashmap_free_' function, allowing the function to free any struct pointer regardless of where the hashmap_entry field is located. `hashmap_free' no longer takes any arguments aside from the hashmap itself. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap: use *_entry APIs to wrap container_ofLibravatar Eric Wong1-9/+5
Using `container_of' can be verbose and choosing names for intermediate "struct hashmap_entry" pointers is a hard problem. So introduce "*_entry" APIs inspired by similar linked-list APIs in the Linux kernel. Unfortunately, `__typeof__' is not portable C, so we need an extra parameter to specify the type. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_get_next returns "struct hashmap_entry *"Libravatar Eric Wong1-4/+7
This is a step towards removing the requirement for hashmap_entry being the first field of a struct. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_add takes "struct hashmap_entry *"Libravatar Eric Wong1-1/+1
This is less error-prone than "void *" as the compiler now detects invalid types being passed. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_get_next takes "const struct hashmap_entry *"Libravatar Eric Wong1-1/+1
This is less error-prone than "const void *" as the compiler now detects invalid types being passed. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_entry_init takes "struct hashmap_entry *"Libravatar Eric Wong1-1/+1
C compilers do type checking to make life easier for us. So rely on that and update all hashmap_entry_init callers to take "struct hashmap_entry *" to avoid future bugs while improving safety and readability. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>