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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>
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1 parent 545f229 commit 4a4e6fd74f7d4564ed43eaaf59b6bd70c1959f1a @sigprof sigprof committed with Junio C Hamano Nov 15, 2005
Showing with 116 additions and 42 deletions.
  1. +16 −3 commit.c
  2. +13 −9 fsck-objects.c
  3. +44 −18 object.c
  4. +8 −2 object.h
  5. +18 −7 server-info.c
  6. +5 −2 tag.c
  7. +12 −1 tree.c
View
@@ -204,6 +204,7 @@ int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
unsigned char parent[20];
struct commit_list **pptr;
struct commit_graft *graft;
+ unsigned n_refs = 0;
if (item->object.parsed)
return 0;
@@ -214,7 +215,7 @@ int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
return error("bad tree pointer in commit %s\n", sha1_to_hex(item->object.sha1));
item->tree = lookup_tree(parent);
if (item->tree)
- add_ref(&item->object, &item->tree->object);
+ n_refs++;
bufptr += 46; /* "tree " + "hex sha1" + "\n" */
pptr = &item->parents;
@@ -230,7 +231,7 @@ int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
new_parent = lookup_commit(parent);
if (new_parent) {
pptr = &commit_list_insert(new_parent, pptr)->next;
- add_ref(&item->object, &new_parent->object);
+ n_refs++;
}
}
if (graft) {
@@ -241,10 +242,22 @@ int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
if (!new_parent)
continue;
pptr = &commit_list_insert(new_parent, pptr)->next;
- add_ref(&item->object, &new_parent->object);
+ n_refs++;
}
}
item->date = parse_commit_date(bufptr);
+
+ if (track_object_refs) {
+ unsigned i = 0;
+ struct commit_list *p;
+ struct object_refs *refs = alloc_object_refs(n_refs);
+ if (item->tree)
+ refs->ref[i++] = &item->tree->object;
+ for (p = item->parents; p; p = p->next)
+ refs->ref[i++] = &p->item->object;
+ set_object_refs(&item->object, refs);
+ }
+
return 0;
}
View
@@ -56,7 +56,6 @@ static void check_connectivity(void)
/* Look up all the requirements, warn about missing objects.. */
for (i = 0; i < nr_objs; i++) {
struct object *obj = objs[i];
- struct object_list *refs;
if (!obj->parsed) {
if (!standalone && has_sha1_file(obj->sha1))
@@ -67,14 +66,19 @@ static void check_connectivity(void)
continue;
}
- for (refs = obj->refs; refs; refs = refs->next) {
- if (refs->item->parsed ||
- (!standalone && has_sha1_file(refs->item->sha1)))
- continue;
- printf("broken link from %7s %s\n",
- obj->type, sha1_to_hex(obj->sha1));
- printf(" to %7s %s\n",
- refs->item->type, sha1_to_hex(refs->item->sha1));
+ if (obj->refs) {
+ const struct object_refs *refs = obj->refs;
+ unsigned j;
+ for (j = 0; j < refs->count; j++) {
+ struct object *ref = refs->ref[j];
+ if (ref->parsed ||
+ (!standalone && has_sha1_file(ref->sha1)))
+ continue;
+ printf("broken link from %7s %s\n",
+ obj->type, sha1_to_hex(obj->sha1));
+ printf(" to %7s %s\n",
+ ref->type, sha1_to_hex(ref->sha1));
+ }
}
if (show_unreachable && !(obj->flags & REACHABLE)) {
View
@@ -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;
+ /* 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);
}
- target->used = 1;
- p = xmalloc(sizeof(*p));
- p->item = target;
- p->next = NULL;
- *pp = p;
+ 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);
}
}
View
@@ -7,13 +7,18 @@ struct object_list {
const char *name;
};
+struct object_refs {
+ unsigned count;
+ struct object *ref[0];
+};
+
struct object {
unsigned parsed : 1;
unsigned used : 1;
unsigned int flags;
unsigned char sha1[20];
const char *type;
- struct object_list *refs;
+ struct object_refs *refs;
void *util;
};
@@ -35,7 +40,8 @@ struct object *parse_object(const unsigned char *sha1);
/** Returns the object, with potentially excess memory allocated. **/
struct object *lookup_unknown_object(const unsigned char *sha1);
-void add_ref(struct object *refer, struct object *target);
+struct object_refs *alloc_object_refs(unsigned count);
+void set_object_refs(struct object *obj, struct object_refs *refs);
void mark_reachable(struct object *obj, unsigned int mask);
View
@@ -424,7 +424,6 @@ static void find_pack_info_one(int pack_ix)
{
unsigned char sha1[20];
struct object *o;
- struct object_list *ref;
int i;
struct packed_git *p = info[pack_ix]->p;
int num = num_packed_objects(p);
@@ -437,8 +436,12 @@ static void find_pack_info_one(int pack_ix)
die("corrupt pack file %s?", p->pack_name);
if ((o = lookup_object(sha1)) == NULL)
die("cannot parse %s", sha1_to_hex(sha1));
- for (ref = o->refs; ref; ref = ref->next)
- ref->item->flags = 0;
+ if (o->refs) {
+ struct object_refs *refs = o->refs;
+ int j;
+ for (j = 0; j < refs->count; j++)
+ refs->ref[j]->flags = 0;
+ }
o->flags = 0;
}
@@ -448,8 +451,12 @@ static void find_pack_info_one(int pack_ix)
die("corrupt pack file %s?", p->pack_name);
if ((o = lookup_object(sha1)) == NULL)
die("cannot find %s", sha1_to_hex(sha1));
- for (ref = o->refs; ref; ref = ref->next)
- ref->item->flags |= REFERENCED;
+ if (o->refs) {
+ struct object_refs *refs = o->refs;
+ int j;
+ for (j = 0; j < refs->count; j++)
+ refs->ref[j]->flags |= REFERENCED;
+ }
o->flags |= INTERNAL;
}
@@ -460,8 +467,12 @@ static void find_pack_info_one(int pack_ix)
die("cannot find %s", sha1_to_hex(sha1));
show(o, pack_ix);
- for (ref = o->refs; ref; ref = ref->next)
- show(ref->item, pack_ix);
+ if (o->refs) {
+ struct object_refs *refs = o->refs;
+ int j;
+ for (j = 0; j < refs->count; j++)
+ show(refs->ref[j], pack_ix);
+ }
}
}
View
7 tag.c
@@ -75,8 +75,11 @@ int parse_tag_buffer(struct tag *item, void *data, unsigned long size)
item->tag[taglen] = '\0';
item->tagged = lookup_object_type(object, type);
- if (item->tagged)
- add_ref(&item->object, item->tagged);
+ if (item->tagged && track_object_refs) {
+ struct object_refs *refs = alloc_object_refs(1);
+ refs->ref[0] = item->tagged;
+ set_object_refs(&item->object, refs);
+ }
return 0;
}
View
13 tree.c
@@ -148,6 +148,7 @@ int parse_tree_buffer(struct tree *item, void *buffer, unsigned long size)
{
void *bufptr = buffer;
struct tree_entry_list **list_p;
+ int n_refs = 0;
if (item->object.parsed)
return 0;
@@ -184,11 +185,21 @@ int parse_tree_buffer(struct tree *item, void *buffer, unsigned long size)
obj = &entry->item.blob->object;
}
if (obj)
- add_ref(&item->object, obj);
+ n_refs++;
entry->parent = NULL; /* needs to be filled by the user */
*list_p = entry;
list_p = &entry->next;
}
+
+ if (track_object_refs) {
+ struct tree_entry_list *entry;
+ unsigned i = 0;
+ struct object_refs *refs = alloc_object_refs(n_refs);
+ for (entry = item->entries; entry; entry = entry->next)
+ refs->ref[i++] = entry->item.any;
+ set_object_refs(&item->object, refs);
+ }
+
return 0;
}

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