[PATCH 2/3] read-cache: reduce malloc/free during writing index

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 read-cache.c |   26 ++++++++++++++++++--------
 1 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/read-cache.c b/read-cache.c
index 2dbf923..7b9a989 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1521,12 +1521,19 @@ static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
 	}
 }
 
-static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce)
+static int ce_prepare_ondisk_entry(struct cache_entry *ce,
+				    void **ondisk_p, int *ondisk_size)
 {
 	int size = ondisk_ce_size(ce);
-	struct ondisk_cache_entry *ondisk = xcalloc(1, size);
+	struct ondisk_cache_entry *ondisk;
 	char *name;
-	int result;
+
+	if (size <= *ondisk_size)
+		ondisk = *ondisk_p;
+	else {
+		ondisk = *ondisk_p = xrealloc(*ondisk_p, size);
+		*ondisk_size = size;
+	}
 
 	ondisk->ctime.sec = htonl(ce->ce_ctime.sec);
 	ondisk->mtime.sec = htonl(ce->ce_mtime.sec);
@@ -1549,10 +1556,7 @@ static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce)
 	else
 		name = ondisk->name;
 	memcpy(name, ce->name, ce_namelen(ce));
-
-	result = ce_write(c, fd, ondisk, size);
-	free(ondisk);
-	return result;
+	return size;
 }
 
 static int has_racy_timestamp(struct index_state *istate)
@@ -1588,6 +1592,8 @@ int write_index(struct index_state *istate, int newfd)
 	struct cache_entry **cache = istate->cache;
 	int entries = istate->cache_nr;
 	struct stat st;
+	void *ce_ondisk = NULL;
+	int ce_ondisk_size = 0;
 
 	for (i = removed = extended = 0; i < entries; i++) {
 		if (cache[i]->ce_flags & CE_REMOVE)
@@ -1612,13 +1618,17 @@ int write_index(struct index_state *istate, int newfd)
 
 	for (i = 0; i < entries; i++) {
 		struct cache_entry *ce = cache[i];
+		int size;
+
 		if (ce->ce_flags & CE_REMOVE)
 			continue;
 		if (!ce_uptodate(ce) && is_racy_timestamp(istate, ce))
 			ce_smudge_racily_clean_entry(ce);
-		if (ce_write_entry(&c, newfd, ce) < 0)
+		size = ce_prepare_ondisk_entry(ce, &ce_ondisk, &ce_ondisk_size);
+		if (ce_write(&c, newfd, ce_ondisk, size) < 0)
 			return -1;
 	}
+	free(ce_ondisk);
 
 	/* Write extension data here */
 	if (istate->cache_tree) {
-- 
1.7.8.36.g69ee2