From: Nicolas Pitre <nico@cam.org>
Date: Tue, 16 May 2006 20:29:14 +0000 (-0400)
Subject: improve depth heuristic for maximum delta size
X-Git-Tag: v1.4.0-rc1~133^2
X-Git-Url: https://git.tokkee.org/?a=commitdiff_plain;h=c3b06a69;p=git.git

improve depth heuristic for maximum delta size

This provides a linear decrement on the penalty related to delta depth
instead of being an 1/x function.  With this another 5% reduction is
observed on packs for both the GIT repo and the Linux kernel repo, as
well as fixing a pack size regression in another sample repo I have.

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

diff --git a/pack-objects.c b/pack-objects.c
index b430b02cf..33751797f 100644
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -1037,9 +1037,12 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
 	if (src_entry->depth >= max_depth)
 		return 0;
 
-	/* Now some size filtering euristics. */
+	/* Now some size filtering heuristics. */
 	size = trg_entry->size;
-	max_size = (size/2 - 20) / (src_entry->depth + 1);
+	max_size = size/2 - 20;
+	max_size = max_size * (max_depth - src_entry->depth) / max_depth;
+	if (max_size == 0)
+		return 0;
 	if (trg_entry->delta && trg_entry->delta_size <= max_size)
 		max_size = trg_entry->delta_size-1;
 	src_size = src_entry->size;