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authorNguyễn Thái Ngọc Duy <pclouds@gmail.com>2013-03-17 10:28:06 +0700
committerJunio C Hamano <gitster@pobox.com>2013-03-16 22:57:29 -0700
commitc73592812d36ccc7eccfd0489177970d246fa522 (patch)
tree1e92b0c8fb8cb4bf5bbb10f38cf695785457b2e7
parent03a0fb0ccf48c831060c2243f830b6a12cd8fdf3 (diff)
downloadgit-c73592812d36ccc7eccfd0489177970d246fa522.tar.gz
Preallocate hash tables when the number of inserts are known in advance
This avoids unnecessary re-allocations and reinsertions. On webkit.git (i.e. about 182k inserts to the name hash table), this reduces about 100ms out of 3s user time. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
-rw-r--r--diffcore-rename.c1
-rw-r--r--hash.h7
-rw-r--r--name-hash.c2
3 files changed, 10 insertions, 0 deletions
diff --git a/diffcore-rename.c b/diffcore-rename.c
index 512d0ac5fd..6c7a72fbe7 100644
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@ -389,6 +389,7 @@ static int find_exact_renames(struct diff_options *options)
struct hash_table file_table;
init_hash(&file_table);
+ preallocate_hash(&file_table, rename_src_nr + rename_dst_nr);
for (i = 0; i < rename_src_nr; i++)
insert_file_table(&file_table, -1, i, rename_src[i].p->one);
diff --git a/hash.h b/hash.h
index b875ce67c4..1d43ac0ba0 100644
--- a/hash.h
+++ b/hash.h
@@ -40,4 +40,11 @@ static inline void init_hash(struct hash_table *table)
table->array = NULL;
}
+static inline void preallocate_hash(struct hash_table *table, unsigned int elts)
+{
+ assert(table->size == 0 && table->nr == 0 && table->array == NULL);
+ table->size = elts * 2;
+ table->array = xcalloc(sizeof(struct hash_table_entry), table->size);
+}
+
#endif
diff --git a/name-hash.c b/name-hash.c
index d8d25c23e9..2a1f108247 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -92,6 +92,8 @@ static void lazy_init_name_hash(struct index_state *istate)
if (istate->name_hash_initialized)
return;
+ if (istate->cache_nr)
+ preallocate_hash(&istate->name_hash, istate->cache_nr);
for (nr = 0; nr < istate->cache_nr; nr++)
hash_index_entry(istate, istate->cache[nr]);
istate->name_hash_initialized = 1;