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unpack-trees: reduce malloc in cache-tree walk 

This is a micro optimization that probably only shines on repos with
deep directory structure. Instead of allocating and freeing a new
cache_entry in every iteration, we reuse the last one and only update
the parts that are new each iteration.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Nguyễn Thái Ngọc Duy 2018-08-18 16:41:25 +02:00 committed by Junio C Hamano
parent b4da37380b
commit f1e11c6510
1 changed files with 20 additions and 9 deletions
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29
unpack-trees.c
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@ -685,6 +685,8 @@ static int traverse_by_cache_tree(int pos, int nr_entries, int nr_names,
{
struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
struct unpack_trees_options *o = info->data;
struct cache_entry *tree_ce = NULL;
int ce_len = 0;
int i, d;
if (!o->merge)
@ -699,30 +701,39 @@ static int traverse_by_cache_tree(int pos, int nr_entries, int nr_names,
* get here in the first place.
*/
for (i = 0; i < nr_entries; i++) {
struct cache_entry *tree_ce;
int len, rc;
int new_ce_len, len, rc;
src[0] = o->src_index->cache[pos + i];
len = ce_namelen(src[0]);
tree_ce = xcalloc(1, cache_entry_size(len));
new_ce_len = cache_entry_size(len);
if (new_ce_len > ce_len) {
new_ce_len <<= 1;
tree_ce = xrealloc(tree_ce, new_ce_len);
memset(tree_ce, 0, new_ce_len);
ce_len = new_ce_len;
tree_ce->ce_flags = create_ce_flags(0);
for (d = 1; d <= nr_names; d++)
src[d] = tree_ce;
}
tree_ce->ce_mode = src[0]->ce_mode;
tree_ce->ce_flags = create_ce_flags(0);
tree_ce->ce_namelen = len;
oidcpy(&tree_ce->oid, &src[0]->oid);
memcpy(tree_ce->name, src[0]->name, len + 1);
for (d = 1; d <= nr_names; d++)
src[d] = tree_ce;
rc = call_unpack_fn((const struct cache_entry * const *)src, o);
free(tree_ce);
if (rc < 0)
if (rc < 0) {
free(tree_ce);
return rc;
}
mark_ce_used(src[0], o);
}
free(tree_ce);
if (o->debug_unpack)
printf("Unpacked %d entries from %s to %s using cache-tree\n",
nr_entries,