[PATCH] Preallocate hash tables when the number of inserts are known in advance
- From
Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
- Date
- Mar 17, 2013, 03:28 UTC
- Message-ID
- <1363490886-29729-1-git-send-email-pclouds@gmail.com>
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> --- nd/read-directory-recursive-optim reduces the number of input (from 182k to 11k on webkit) to exclude machinery that all patches in the exclude optimization series I posted seem insignificant. So I won't repost them for inclusion unless you think it has cleanup values.
This one is worth doing though. I think keeping "untracked index" would help avoid looking up in name-hash, where all user-space CPU cycles are spent. But I have nothing to show about that.
diffcore-rename.c | 1 + hash.h | 7 +++++++ name-hash.c | 2 ++ 3 files changed, 10 insertions(+)
diff --git a/diffcore-rename.c b/diffcore-rename.c index 512d0ac..8d3d9bb 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) * 2); 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 b875ce6..244d1fe 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 size) +{ + assert(table->size == 0 && table->nr == 0 && table->array == NULL); + table->size = size; + table->array = xcalloc(sizeof(struct hash_table_entry), size); +} + #endif diff --git a/name-hash.c b/name-hash.c index 942c459..12364d1 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 * 2); for (nr = 0; nr < istate->cache_nr; nr++) hash_index_entry(istate, istate->cache[nr]); istate->name_hash_initialized = 1;
-- 1.8.2.83.gc99314b