pack-object: slightly more efficient

Avoid creating a delta index for objects with maximum depth since they
are not going to be used as delta base anyway.  This also reduce peak
memory usage slightly as the current object's delta index is not useful
until the next object in the loop is considered for deltification. This
saves a bit more than 1% on CPU usage.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

2 files changed, 10 insertions, 7 deletions

diff --git a/delta.h b/delta.h
index 727ae30e9e..7b3f86d85f 100644
--- a/delta.h
+++ b/delta.h
@@ -18,6 +18,8 @@ create_delta_index(const void *buf, unsigned long bufsize);
 
 /*
  * free_delta_index: free the index created by create_delta_index()
+ *
+ * Given pointer must be what create_delta_index() returned, or NULL.
  */
 extern void free_delta_index(struct delta_index *index);
 
diff --git a/pack-objects.c b/pack-objects.c
index 526c090c61..b430b02cf7 100644
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -1105,17 +1105,14 @@ static void find_deltas(struct object_entry **list, int window, int depth)
 
 		if (entry->size < 50)
 			continue;
-		if (n->index)
-			free_delta_index(n->index);
+		free_delta_index(n->index);
+		n->index = NULL;
 		free(n->data);
 		n->entry = entry;
 		n->data = read_sha1_file(entry->sha1, type, &size);
 		if (size != entry->size)
 			die("object %s inconsistent object length (%lu vs %lu)",
 			    sha1_to_hex(entry->sha1), size, entry->size);
-		n->index = create_delta_index(n->data, size);
-		if (!n->index)
-			die("out of memory");
 
 		j = window;
 		while (--j > 0) {
@@ -1135,6 +1132,11 @@ static void find_deltas(struct object_entry **list, int window, int depth)
 		 */
 		if (entry->delta && depth <= entry->depth)
 			continue;
+
+		n->index = create_delta_index(n->data, size);
+		if (!n->index)
+			die("out of memory");
+
 		idx++;
 		if (idx >= window)
 			idx = 0;
@@ -1144,8 +1146,7 @@ static void find_deltas(struct object_entry **list, int window, int depth)
 		fputc('\n', stderr);
 
 	for (i = 0; i < window; ++i) {
-		if (array[i].index)
-			free_delta_index(array[i].index);
+		free_delta_index(array[i].index);
 		free(array[i].data);
 	}
 	free(array);