From 7252d9a036fabb10f60dc09937fc39e252f3c4d4 Mon Sep 17 00:00:00 2001 From: Taylor Blau Date: Thu, 23 May 2024 17:27:21 -0400 Subject: pseudo-merge: implement support for finding existing merges This patch implements support for reusing existing pseudo-merge commits when writing bitmaps when there is an existing pseudo-merge bitmap which has exactly the same set of parents as one that we are about to write. Note that unstable pseudo-merges are likely to change between consecutive repacks, and so are generally poor candidates for reuse. However, stable pseudo-merges (see the configuration option 'bitmapPseudoMerge..stableThreshold') are by definition unlikely to change between runs (as they represent long-running branches). Because there is no index from a *set* of pseudo-merge parents to a matching pseudo-merge bitmap, we have to construct the bitmap corresponding to the set of parents for each pending pseudo-merge commit and see if a matching bitmap exists. This is technically quadratic in the number of pseudo-merges, but is OK in practice for a couple of reasons: - non-matching pseudo-merge bitmaps are rejected quickly as soon as they differ in a single bit - already-matched pseudo-merge bitmaps are discarded from subsequent rounds of search - the number of pseudo-merges is generally small, even for large repositories In order to do this, implement (a) a function that finds a matching pseudo-merge given some uncompressed bitset describing its parents, (b) a function that computes the bitset of parents for a given pseudo-merge commit, and (c) call that function before computing the set of reachable objects for some pending pseudo-merge. Signed-off-by: Taylor Blau Signed-off-by: Junio C Hamano --- pack-bitmap.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'pack-bitmap.c') diff --git a/pack-bitmap.c b/pack-bitmap.c index 1966b3b95f..70230e2647 100644 --- a/pack-bitmap.c +++ b/pack-bitmap.c @@ -1316,6 +1316,37 @@ cleanup: return cb.base; } +struct ewah_bitmap *pseudo_merge_bitmap_for_commit(struct bitmap_index *bitmap_git, + struct commit *commit) +{ + struct commit_list *p; + struct bitmap *parents; + struct pseudo_merge *match = NULL; + + if (!bitmap_git->pseudo_merges.nr) + return NULL; + + parents = bitmap_new(); + + for (p = commit->parents; p; p = p->next) { + int pos = bitmap_position(bitmap_git, &p->item->object.oid); + if (pos < 0 || pos >= bitmap_num_objects(bitmap_git)) + goto done; + + bitmap_set(parents, pos); + } + + match = pseudo_merge_for_parents(&bitmap_git->pseudo_merges, + parents); + +done: + bitmap_free(parents); + if (match) + return pseudo_merge_bitmap(&bitmap_git->pseudo_merges, match); + + return NULL; +} + static void unsatisfy_all_pseudo_merges(struct bitmap_index *bitmap_git) { uint32_t i; @@ -2809,6 +2840,7 @@ void free_bitmap_index(struct bitmap_index *b) */ close_midx_revindex(b->midx); } + free_pseudo_merge_map(&b->pseudo_merges); free(b); } -- cgit v1.3