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From: git@jeffhostetler.com
To: git@vger.kernel.org
Cc: gitster@pobox.com, peff@peff.net,
	Jeff Hostetler <jeffhost@microsoft.com>
Subject: [PATCH v4 4/4] read-cache: speed up add_index_entry during checkout
Date: Tue,  4 Apr 2017 21:08:47 +0000	[thread overview]
Message-ID: <20170404210847.50860-5-git@jeffhostetler.com> (raw)
In-Reply-To: <20170404210847.50860-1-git@jeffhostetler.com>

From: Jeff Hostetler <jeffhost@microsoft.com>

Teach add_index_entry_with_check() and has_dir_name()
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 saves at least 2
lookups per file.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
---
 read-cache.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/read-cache.c b/read-cache.c
index b3fc77d..bf9fc53 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -927,6 +927,21 @@ static int has_dir_name(struct index_state *istate,
 	int stage = ce_stage(ce);
 	const char *name = ce->name;
 	const char *slash = name + ce_namelen(ce);
+	int len_eq_last;
+	int cmp_last = 0;
+
+	if (istate->cache_nr > 0) {
+		/*
+		 * Compare the entry's full path with the last path in the index.
+		 * If it sorts AFTER the last entry in the index and they have no
+		 * common prefix, then there cannot be any F/D name conflicts.
+		 */
+		cmp_last = strcmp_offset(name,
+			istate->cache[istate->cache_nr-1]->name,
+			&len_eq_last);
+		if (cmp_last > 0 && len_eq_last == 0)
+			return retval;
+	}
 
 	for (;;) {
 		int len;
@@ -939,6 +954,24 @@ static int has_dir_name(struct index_state *istate,
 		}
 		len = slash - name;
 
+		if (cmp_last > 0) {
+			/*
+			 * If this part of the directory prefix (including the trailing
+			 * slash) already appears in the path of the last entry in the
+			 * index, then we cannot also have a file with this prefix (or
+			 * any parent directory prefix).
+			 */
+			if (len+1 <= len_eq_last)
+				return retval;
+			/*
+			 * If this part of the directory prefix (excluding the trailing
+			 * slash) is longer than the known equal portions, then this part
+			 * of the prefix cannot collide with a file.  Go on to the parent.
+			 */
+			if (len > len_eq_last)
+				continue;
+		}
+
 		pos = index_name_stage_pos(istate, name, len, stage);
 		if (pos >= 0) {
 			/*
@@ -1030,7 +1063,16 @@ 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) {
-- 
2.9.3


      parent reply	other threads:[~2017-04-04 21:09 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-04 21:08 [PATCH v4 0/4] read-cache: speed up add_index_entry git
2017-04-04 21:08 ` [PATCH v4 1/4] p0004-read-tree: perf test to time read-tree git
2017-04-04 21:08 ` [PATCH v4 2/4] read-cache: add strcmp_offset function git
2017-04-04 21:08 ` [PATCH v4 3/4] test-strcmp-offset: created test for strcmp_offset git
2017-04-04 21:08 ` git [this message]

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