Pass the comparison function to cmp_items() via the context parameter of
qsort_s() instead of using a global variable. That allows calling
string_list_sort() from multiple parallel threads.
Our qsort_s() in compat/ is slightly slower than qsort(1) from glibc
2.24 for sorting lots of lines:
Test HEAD^ HEAD
---------------------------------------------------------------------
0071.2: sort(1) 0.10(0.22+0.01) 0.09(0.21+0.00) -10.0%
0071.3: string_list_sort() 0.16(0.15+0.01) 0.17(0.15+0.00) +6.3%
GNU sort(1) version 8.26 is significantly faster because it uses
multiple parallel threads; with the unportable option --parallel=1 it
becomes slower:
Test HEAD^ HEAD
--------------------------------------------------------------------
0071.2: sort(1) 0.21(0.18+0.01) 0.20(0.18+0.01) -4.8%
0071.3: string_list_sort() 0.16(0.13+0.02) 0.17(0.15+0.01) +6.3%
There is some instability -- the numbers for the sort(1) check shouldn't
be affected by this patch. Anyway, the performance of our qsort_s()
implementation is apparently good enough, at least for this test.
Signed-off-by: Rene Scharfe <l.s.r@xxxxxx>
---
string-list.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)
diff --git a/string-list.c b/string-list.c
index 8c83cac189..45016ad86d 100644
--- a/string-list.c
+++ b/string-list.c
@@ -211,21 +211,18 @@ struct string_list_item *string_list_append(struct string_list *list,
list->strdup_strings ? xstrdup(string) : (char *)string);
}
-/* Yuck */
-static compare_strings_fn compare_for_qsort;
-
-/* Only call this from inside string_list_sort! */
-static int cmp_items(const void *a, const void *b)
+static int cmp_items(const void *a, const void *b, void *ctx)
{
+ compare_strings_fn cmp = ctx;
const struct string_list_item *one = a;
const struct string_list_item *two = b;
- return compare_for_qsort(one->string, two->string);
+ return cmp(one->string, two->string);
}
void string_list_sort(struct string_list *list)
{
- compare_for_qsort = list->cmp ? list->cmp : strcmp;
- QSORT(list->items, list->nr, cmp_items);
+ QSORT_S(list->items, list->nr, cmp_items,
+ list->cmp ? list->cmp : strcmp);
}
struct string_list_item *unsorted_string_list_lookup(struct string_list *list,
--
2.11.0