Merge branch 'jc/pack'

* jc/pack:
  pack-objects: simplify "thin" pack.
  verify-pack -v: show delta-chain histogram.

2 files changed, 30 insertions, 28 deletions

diff --git a/pack-check.c b/pack-check.c
index eca32b6ca..84ed90d36 100644
--- a/pack-check.c
+++ b/pack-check.c
@@ -70,13 +70,17 @@ static int verify_packfile(struct packed_git *p)
 }
 
 
+#define MAX_CHAIN 40
+
 static void show_pack_info(struct packed_git *p)
 {
 	struct pack_header *hdr;
 	int nr_objects, i;
+	unsigned int chain_histogram[MAX_CHAIN];
 
 	hdr = p->pack_base;
 	nr_objects = ntohl(hdr->hdr_entries);
+	memset(chain_histogram, 0, sizeof(chain_histogram));
 
 	for (i = 0; i < nr_objects; i++) {
 		unsigned char sha1[20], base_sha1[20];
@@ -97,11 +101,25 @@ static void show_pack_info(struct packed_git *p)
 		printf("%s ", sha1_to_hex(sha1));
 		if (!delta_chain_length)
 			printf("%-6s %lu %u\n", type, size, e.offset);
-		else
+		else {
 			printf("%-6s %lu %u %u %s\n", type, size, e.offset,
 			       delta_chain_length, sha1_to_hex(base_sha1));
+			if (delta_chain_length < MAX_CHAIN)
+				chain_histogram[delta_chain_length]++;
+			else
+				chain_histogram[0]++;
+		}
 	}
 
+	for (i = 0; i < MAX_CHAIN; i++) {
+		if (!chain_histogram[i])
+			continue;
+		printf("chain length %s %d: %d object%s\n",
+		       i ? "=" : ">=",
+		       i ? i : MAX_CHAIN,
+		       chain_histogram[i],
+		       1 < chain_histogram[i] ? "s" : "");
+	}
 }
 
 int verify_pack(struct packed_git *p, int verbose)
diff --git a/pack-objects.c b/pack-objects.c
index 136a7f5aa..49357c673 100644
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -32,9 +32,6 @@ struct object_entry {
 				 * be used as the base objectto delta huge
 				 * objects against.
 				 */
-	int based_on_preferred;	/* current delta candidate is a preferred
-				 * one, or delta against a preferred one.
-				 */
 };
 
 /*
@@ -824,8 +821,6 @@ static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_de
 {
 	struct object_entry *cur_entry = cur->entry;
 	struct object_entry *old_entry = old->entry;
-	int old_preferred = (old_entry->preferred_base ||
-			     old_entry->based_on_preferred);
 	unsigned long size, oldsize, delta_size, sizediff;
 	long max_size;
 	void *delta_buf;
@@ -867,27 +862,8 @@ static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_de
 	 * delete).
 	 */
 	max_size = size / 2 - 20;
-	if (cur_entry->delta) {
-		if (cur_entry->based_on_preferred) {
-			if (old_preferred)
-				max_size = cur_entry->delta_size-1;
-			else
-				/* trying with non-preferred one when we
-				 * already have a delta based on preferred
-				 * one is pointless.
-				 */
-				return -1;
-		}
-		else if (!old_preferred)
-			max_size = cur_entry->delta_size-1;
-		else
-			/* otherwise...  even if delta with a
-			 * preferred one produces a bigger result than
-			 * what we currently have, which is based on a
-			 * non-preferred one, it is OK.
-			 */
-			;
-	}
+	if (cur_entry->delta)
+		max_size = cur_entry->delta_size-1;
 	if (sizediff >= max_size)
 		return -1;
 	delta_buf = diff_delta(old->data, oldsize,
@@ -897,7 +873,6 @@ static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_de
 	cur_entry->delta = old_entry;
 	cur_entry->delta_size = delta_size;
 	cur_entry->depth = old_entry->depth + 1;
-	cur_entry->based_on_preferred = old_preferred;
 	free(delta_buf);
 	return 0;
 }
@@ -966,6 +941,15 @@ static void find_deltas(struct object_entry **list, int window, int depth)
 			if (try_delta(n, m, depth) < 0)
 				break;
 		}
+#if 0
+		/* if we made n a delta, and if n is already at max
+		 * depth, leaving it in the window is pointless.  we
+		 * should evict it first.
+		 * ... in theory only; somehow this makes things worse.
+		 */
+		if (entry->delta && depth <= entry->depth)
+			continue;
+#endif
 		idx++;
 		if (idx >= window)
 			idx = 0;