Rework object refs tracking to reduce memory usage
Store pointers to referenced objects in a variable sized array instead
of linked list. This cuts down memory usage of utilities which use
object references; e.g., git-fsck-objects --full on the git.git
repository consumes about 2 MB of memory tracked by Massif instead of
7 MB before the change. Object refs are still the biggest consumer of
memory (57%), but the malloc overhead for a single block instead of a
linked list is substantially smaller.
Signed-off-by: Sergey Vlasov <vsu@altlinux.ru>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/object.c b/object.c
index 1fdebe0..427e14c 100644
--- a/object.c
+++ b/object.c
@@ -67,40 +67,66 @@
nr_objs++;
}
-void add_ref(struct object *refer, struct object *target)
+struct object_refs *alloc_object_refs(unsigned count)
{
- struct object_list **pp, *p;
+ struct object_refs *refs;
+ size_t size = sizeof(*refs) + count*sizeof(struct object *);
- if (!track_object_refs)
+ refs = xmalloc(size);
+ memset(refs, 0, size);
+ refs->count = count;
+ return refs;
+}
+
+static int compare_object_pointers(const void *a, const void *b)
+{
+ const struct object * const *pa = a;
+ const struct object * const *pb = b;
+ return *pa - *pb;
+}
+
+void set_object_refs(struct object *obj, struct object_refs *refs)
+{
+ unsigned int i, j;
+
+ /* Do not install empty list of references */
+ if (refs->count < 1) {
+ free(refs);
return;
-
- pp = &refer->refs;
- while ((p = *pp) != NULL) {
- if (p->item == target)
- return;
- pp = &p->next;
}
- target->used = 1;
- p = xmalloc(sizeof(*p));
- p->item = target;
- p->next = NULL;
- *pp = p;
+ /* Sort the list and filter out duplicates */
+ qsort(refs->ref, refs->count, sizeof(refs->ref[0]),
+ compare_object_pointers);
+ for (i = j = 1; i < refs->count; i++) {
+ if (refs->ref[i] != refs->ref[i - 1])
+ refs->ref[j++] = refs->ref[i];
+ }
+ if (j < refs->count) {
+ /* Duplicates were found - reallocate list */
+ size_t size = sizeof(*refs) + j*sizeof(struct object *);
+ refs->count = j;
+ refs = xrealloc(refs, size);
+ }
+
+ for (i = 0; i < refs->count; i++)
+ refs->ref[i]->used = 1;
+ obj->refs = refs;
}
void mark_reachable(struct object *obj, unsigned int mask)
{
- struct object_list *p = obj->refs;
-
if (!track_object_refs)
die("cannot do reachability with object refs turned off");
/* If we've been here already, don't bother */
if (obj->flags & mask)
return;
obj->flags |= mask;
- while (p) {
- mark_reachable(p->item, mask);
- p = p->next;
+ if (obj->refs) {
+ const struct object_refs *refs = obj->refs;
+ unsigned i;
+ for (i = 0; i < refs->count; i++)
+ mark_reachable(refs->ref[i], mask);
}
}
