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>
This commit is contained in:
Nguyễn Thái Ngọc Duy
2013-03-17 10:28:06 +07:00
committed by Junio C Hamano
parent 03a0fb0ccf
commit c73592812d
3 changed files with 10 additions and 0 deletions

7
hash.h
View File

@@ -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