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Rework object refs tracking to reduce memory usage

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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>
This commit is contained in:
Sergey Vlasov
2005-11-15 19:08:08 +03:00
committed by Junio C Hamano
parent 545f229a4b
commit 4a4e6fd74f
7 changed files with 117 additions and 43 deletions
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64
object.c
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@ -67,40 +67,66 @@ void created_object(const unsigned char *sha1, struct object *obj)
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);
}
}