From: Jeff Hostetler <jeffhost@microsoft.com>
Date: Wed, 19 Apr 2017 17:06:16 +0000 (+0000)
Subject: read-cache: speed up add_index_entry during checkout
X-Git-Tag: v2.13.0-rc1~8^2~2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e5494631ed94017da862d55eb6393a0d01d8b91d;p=thirdparty%2Fgit.git

read-cache: speed up add_index_entry during checkout

Teach add_index_entry_with_check() to see if the path
of the new item is greater than the last path in the
index array before attempting to search for it.

During checkout, merge_working_tree() populates the new
index in sorted order, so this change will save a binary
lookups per file.  This preserves the original behavior
but simply checks the last element before starting the
search.

This helps performance on very large repositories.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

diff --git a/read-cache.c b/read-cache.c
index 11823f5dbc..836338b3ba 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1021,7 +1021,16 @@ static int add_index_entry_with_check(struct index_state *istate, struct cache_e
 
 	if (!(option & ADD_CACHE_KEEP_CACHE_TREE))
 		cache_tree_invalidate_path(istate, ce->name);
-	pos = index_name_stage_pos(istate, ce->name, ce_namelen(ce), ce_stage(ce));
+
+	/*
+	 * If this entry's path sorts after the last entry in the index,
+	 * we can avoid searching for it.
+	 */
+	if (istate->cache_nr > 0 &&
+		strcmp(ce->name, istate->cache[istate->cache_nr - 1]->name) > 0)
+		pos = -istate->cache_nr - 1;
+	else
+		pos = index_name_stage_pos(istate, ce->name, ce_namelen(ce), ce_stage(ce));
 
 	/* existing match? Just replace it. */
 	if (pos >= 0) {