speed up alt_odb_usable() with many alternates
With many alternates, the duplicate check in alt_odb_usable()
wastes many cycles doing repeated fspathcmp() on every existing
alternate. Use a khash to speed up lookups by odb->path.
Since the kh_put_* API uses the supplied key without
duplicating it, we also take advantage of it to replace both
xstrdup() and strbuf_release() in link_alt_odb_entry() with
strbuf_detach() to avoid the allocation and copy.
In a test repository with 50K alternates and each of those 50K
alternates having one alternate each (for a total of 100K total
alternates); this speeds up lookup of a non-existent blob from
over 16 minutes to roughly 2.7 seconds on my busy workstation.
Note: all underlying git object directories were small and
unpacked with only loose objects and no packs. Having to load
packs increases times significantly.
Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/object-file.c b/object-file.c
index f233b44..a13f49b 100644
--- a/object-file.c
+++ b/object-file.c
@@ -517,9 +517,9 @@ const char *loose_object_path(struct repository *r, struct strbuf *buf,
*/
static int alt_odb_usable(struct raw_object_store *o,
struct strbuf *path,
- const char *normalized_objdir)
+ const char *normalized_objdir, khiter_t *pos)
{
- struct object_directory *odb;
+ int r;
/* Detect cases where alternate disappeared */
if (!is_directory(path->buf)) {
@@ -533,14 +533,20 @@ static int alt_odb_usable(struct raw_object_store *o,
* Prevent the common mistake of listing the same
* thing twice, or object directory itself.
*/
- for (odb = o->odb; odb; odb = odb->next) {
- if (!fspathcmp(path->buf, odb->path))
- return 0;
- }
- if (!fspathcmp(path->buf, normalized_objdir))
- return 0;
+ if (!o->odb_by_path) {
+ khiter_t p;
- return 1;
+ o->odb_by_path = kh_init_odb_path_map();
+ assert(!o->odb->next);
+ p = kh_put_odb_path_map(o->odb_by_path, o->odb->path, &r);
+ assert(r == 1); /* never used */
+ kh_value(o->odb_by_path, p) = o->odb;
+ }
+ if (fspatheq(path->buf, normalized_objdir))
+ return 0;
+ *pos = kh_put_odb_path_map(o->odb_by_path, path->buf, &r);
+ /* r: 0 = exists, 1 = never used, 2 = deleted */
+ return r == 0 ? 0 : 1;
}
/*
@@ -566,6 +572,7 @@ static int link_alt_odb_entry(struct repository *r, const char *entry,
{
struct object_directory *ent;
struct strbuf pathbuf = STRBUF_INIT;
+ khiter_t pos;
if (!is_absolute_path(entry) && relative_base) {
strbuf_realpath(&pathbuf, relative_base, 1);
@@ -587,23 +594,25 @@ static int link_alt_odb_entry(struct repository *r, const char *entry,
while (pathbuf.len && pathbuf.buf[pathbuf.len - 1] == '/')
strbuf_setlen(&pathbuf, pathbuf.len - 1);
- if (!alt_odb_usable(r->objects, &pathbuf, normalized_objdir)) {
+ if (!alt_odb_usable(r->objects, &pathbuf, normalized_objdir, &pos)) {
strbuf_release(&pathbuf);
return -1;
}
CALLOC_ARRAY(ent, 1);
- ent->path = xstrdup(pathbuf.buf);
+ /* pathbuf.buf is already in r->objects->odb_by_path */
+ ent->path = strbuf_detach(&pathbuf, NULL);
/* add the alternate entry */
*r->objects->odb_tail = ent;
r->objects->odb_tail = &(ent->next);
ent->next = NULL;
+ assert(r->objects->odb_by_path);
+ kh_value(r->objects->odb_by_path, pos) = ent;
/* recursively add alternates */
- read_info_alternates(r, pathbuf.buf, depth + 1);
+ read_info_alternates(r, ent->path, depth + 1);
- strbuf_release(&pathbuf);
return 0;
}
