string-list: use ALLOC_GROW macro when reallocing string_list

Use ALLOC_GROW() macro when reallocing a string_list array
rather than simply increasing it by 32.  This is a performance
optimization.

During status on a very large repo and there are many changes,
a significant percentage of the total run time is spent
reallocing the wt_status.changes array.

This change decreases the time in wt_status_collect_changes_worktree()
from 125 seconds to 45 seconds on my very large repository.

This produced a modest gain on my 1M file artificial repo, but
broke even on linux.git.

Test                                            HEAD^^            HEAD
---------------------------------------------------------------------------------------
0005.2: read-tree status br_ballast (1000001)   8.29(5.62+2.62)   8.22(5.57+2.63) -0.8%

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff Hostetler
2017-04-14 19:51:52 +00:00
committed by Junio C Hamano
parent 3b9e3c2ced
commit 950a234cbd
2 changed files with 50 additions and 4 deletions

View File

@ -41,10 +41,7 @@ static int add_entry(int insert_at, struct string_list *list, const char *string
if (exact_match)
return -1 - index;
if (list->nr + 1 >= list->alloc) {
list->alloc += 32;
REALLOC_ARRAY(list->items, list->alloc);
}
ALLOC_GROW(list->items, list->nr+1, list->alloc);
if (index < list->nr)
memmove(list->items + index + 1, list->items + index,
(list->nr - index)