pack-objects: enable multi-pack reuse via feature.experimental

Now that multi-pack reuse is supported, enable it via the feature.experimental configuration in addition to the classic `pack.allowPackReuse`. This will allow more users to experiment with the new behavior who might not otherwise be aware of the existing `pack.allowPackReuse` configuration option. The enum with values NO_PACK_REUSE, SINGLE_PACK_REUSE, and MULTI_PACK_REUSE is defined statically in builtin/pack-objects.c's compilation unit. We could hoist that enum into a scope visible from the repository_settings struct, and then use that enum value in pack-objects. Instead, define a single int that indicates what pack-objects's default value should be to avoid additional unnecessary code movement. Though `feature.experimental` implies `pack.allowPackReuse=multi`, this can still be overridden by explicitly setting the latter configuration to either "single" or "false". Tests covering all of these cases are showin t5332. Signed-off-by: Taylor Blau <[email protected]> Signed-off-by: Junio C Hamano <[email protected]>
ToBoMi · Feb 5, 2024 · 23c1e71 · 23c1e71
1 parent 7c01878
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diff --git a/Documentation/config/feature.txt b/Documentation/config/feature.txt
@@ -17,6 +17,9 @@ skipping more commits at a time, reducing the number of round trips.
 +
 * `pack.useBitmapBoundaryTraversal=true` may improve bitmap traversal times by
 walking fewer objects.
++
+* `pack.allowPackReuse=multi` may improve the time it takes to create a pack by
+reusing objects from multiple packs instead of just one.
 
 feature.manyFiles::
 	Enable config options that optimize for repos with many files in the

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
@@ -4396,6 +4396,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 		prepare_repo_settings(the_repository);
 		if (sparse < 0)
 			sparse = the_repository->settings.pack_use_sparse;
+		if (the_repository->settings.pack_use_multi_pack_reuse)
+			allow_pack_reuse = MULTI_PACK_REUSE;
 	}
 
 	reset_pack_idx_option(&pack_idx_opts);

diff --git a/repo-settings.c b/repo-settings.c
@@ -43,6 +43,7 @@ void prepare_repo_settings(struct repository *r)
 	if (experimental) {
 		r->settings.fetch_negotiation_algorithm = FETCH_NEGOTIATION_SKIPPING;
 		r->settings.pack_use_bitmap_boundary_traversal = 1;
+		r->settings.pack_use_multi_pack_reuse = 1;
 	}
 	if (manyfiles) {
 		r->settings.index_version = 4;

diff --git a/repository.h b/repository.h
@@ -39,6 +39,7 @@ struct repo_settings {
 	int sparse_index;
 	int pack_read_reverse_index;
 	int pack_use_bitmap_boundary_traversal;
+	int pack_use_multi_pack_reuse;
 
 	/*
 	 * Does this repository have core.useReplaceRefs=true (on by

diff --git a/t/t5332-multi-pack-reuse.sh b/t/t5332-multi-pack-reuse.sh
@@ -58,6 +58,22 @@ test_expect_success 'preferred pack is reused for single-pack reuse' '
 	test_pack_objects_reused_all 3 1
 '
 
+test_expect_success 'multi-pack reuse is disabled by default' '
+	test_pack_objects_reused_all 3 1
+'
+
+test_expect_success 'feature.experimental implies multi-pack reuse' '
+	test_config feature.experimental true &&
+
+	test_pack_objects_reused_all 6 2
+'
+
+test_expect_success 'multi-pack reuse can be disabled with feature.experimental' '
+	test_config feature.experimental true &&
+	test_config pack.allowPackReuse single &&
+
+	test_pack_objects_reused_all 3 1
+'
 
 test_expect_success 'enable multi-pack reuse' '
 	git config pack.allowPackReuse multi