Merge branch 'jk/pack-delta-reuse-with-bitmap'

When creating a thin pack, which allows objects to be made into a
delta against another object that is not in the resulting pack but
is known to be present on the receiving end, the code learned to
take advantage of the reachability bitmap; this allows the server
to send a delta against a base beyond the "boundary" commit.

* jk/pack-delta-reuse-with-bitmap:
  pack-objects: reuse on-disk deltas for thin "have" objects
  pack-bitmap: save "have" bitmap from walk
  t/perf: add perf tests for fetches from a bitmapped server
  t/perf: add infrastructure for measuring sizes
  t/perf: factor out percent calculations
  t/perf: factor boilerplate out of test_perf

1 files changed, 19 insertions, 9 deletions

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index caa4cd0211..f434e1fb0c 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -41,6 +41,7 @@
 #define DELTA_CHILD(obj) oe_delta_child(&to_pack, obj)
 #define DELTA_SIBLING(obj) oe_delta_sibling(&to_pack, obj)
 #define SET_DELTA(obj, val) oe_set_delta(&to_pack, obj, val)
+#define SET_DELTA_EXT(obj, oid) oe_set_delta_ext(&to_pack, obj, oid)
 #define SET_DELTA_SIZE(obj, val) oe_set_delta_size(&to_pack, obj, val)
 #define SET_DELTA_CHILD(obj, val) oe_set_delta_child(&to_pack, obj, val)
 #define SET_DELTA_SIBLING(obj, val) oe_set_delta_sibling(&to_pack, obj, val)
@@ -60,6 +61,7 @@ static struct packing_data to_pack;
 
 static struct pack_idx_entry **written_list;
 static uint32_t nr_result, nr_written, nr_seen;
+static struct bitmap_index *bitmap_git;
 
 static int non_empty;
 static int reuse_delta = 1, reuse_object = 1;
@@ -80,6 +82,7 @@ static unsigned long pack_size_limit;
 static int depth = 50;
 static int delta_search_threads;
 static int pack_to_stdout;
+static int thin;
 static int num_preferred_base;
 static struct progress *progress_state;
 
@@ -1538,11 +1541,15 @@ static void check_object(struct object_entry *entry)
 			break;
 		}
 
-		if (base_ref && (base_entry = packlist_find(&to_pack, base_ref, NULL))) {
+		if (base_ref && (
+		    (base_entry = packlist_find(&to_pack, base_ref, NULL)) ||
+		    (thin &&
+		     bitmap_has_sha1_in_uninteresting(bitmap_git, base_ref)))) {
 			/*
 			 * If base_ref was set above that means we wish to
-			 * reuse delta data, and we even found that base
-			 * in the list of objects we want to pack. Goodie!
+			 * reuse delta data, and either we found that object in
+			 * the list of objects we want to pack, or it's one we
+			 * know the receiver has.
 			 *
 			 * Depth value does not matter - find_deltas() will
 			 * never consider reused delta as the base object to
@@ -1551,10 +1558,16 @@ static void check_object(struct object_entry *entry)
 			 */
 			oe_set_type(entry, entry->in_pack_type);
 			SET_SIZE(entry, in_pack_size); /* delta size */
-			SET_DELTA(entry, base_entry);
 			SET_DELTA_SIZE(entry, in_pack_size);
-			entry->delta_sibling_idx = base_entry->delta_child_idx;
-			SET_DELTA_CHILD(base_entry, entry);
+
+			if (base_entry) {
+				SET_DELTA(entry, base_entry);
+				entry->delta_sibling_idx = base_entry->delta_child_idx;
+				SET_DELTA_CHILD(base_entry, entry);
+			} else {
+				SET_DELTA_EXT(entry, base_ref);
+			}
+
 			unuse_pack(&w_curs);
 			return;
 		}
@@ -2979,7 +2992,6 @@ static int pack_options_allow_reuse(void)
 
 static int get_object_list_from_bitmap(struct rev_info *revs)
 {
-	struct bitmap_index *bitmap_git;
 	if (!(bitmap_git = prepare_bitmap_walk(revs)))
 		return -1;
 
@@ -2995,7 +3007,6 @@ static int get_object_list_from_bitmap(struct rev_info *revs)
 	}
 
 	traverse_bitmap_commit_list(bitmap_git, &add_object_entry_from_bitmap);
-	free_bitmap_index(bitmap_git);
 	return 0;
 }
 
@@ -3143,7 +3154,6 @@ static int option_parse_unpack_unreachable(const struct option *opt,
 int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 {
 	int use_internal_rev_list = 0;
-	int thin = 0;
 	int shallow = 0;
 	int all_progress_implied = 0;
 	struct argv_array rp = ARGV_ARRAY_INIT;