mirror of
https://github.com/git/git
synced 2024-08-27 11:39:22 +00:00
commit: allow associating auxiliary info on-demand
The "indegree" field in the commit object is only used while sorting a list of commits in topological order, and wasting memory otherwise. We would prefer to shrink the size of individual commit objects, which we may have to hold thousands of in-core. We could eject "indegree" field out from the commit object and represent it as a dynamic table based on the decoration infrastructure, but the decoration is meant for sparse annotation and is not a good match. Instead, let's try a different approach. - Assign an integer (commit->index) to each commit we keep in-core (reuse the space of "indegree" field for it); - When running the topological sort, allocate an array of integers in bulk (called "slab"), use the commit->index as an index into this array, and store the "indegree" information there. This does _not_ reduce the memory footprint of a commit object, but the commit->index can be used as the index to dynamically associate commits with other kinds of information as needed. Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
parent
a46221e9ad
commit
96c4f4a370
59
commit.c
59
commit.c
|
@ -14,6 +14,7 @@ static struct commit_extra_header *read_commit_extra_header_lines(const char *bu
|
|||
int save_commit_buffer = 1;
|
||||
|
||||
const char *commit_type = "commit";
|
||||
static int commit_count;
|
||||
|
||||
static struct commit *check_commit(struct object *obj,
|
||||
const unsigned char *sha1,
|
||||
|
@ -58,8 +59,11 @@ struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_n
|
|||
struct commit *lookup_commit(const unsigned char *sha1)
|
||||
{
|
||||
struct object *obj = lookup_object(sha1);
|
||||
if (!obj)
|
||||
return create_object(sha1, OBJ_COMMIT, alloc_commit_node());
|
||||
if (!obj) {
|
||||
struct commit *c = alloc_commit_node();
|
||||
c->index = commit_count++;
|
||||
return create_object(sha1, OBJ_COMMIT, c);
|
||||
}
|
||||
if (!obj->type)
|
||||
obj->type = OBJ_COMMIT;
|
||||
return check_commit(obj, sha1, 0);
|
||||
|
@ -497,6 +501,36 @@ struct commit *pop_commit(struct commit_list **stack)
|
|||
return item;
|
||||
}
|
||||
|
||||
struct commit_slab {
|
||||
int *buf;
|
||||
int alloc;
|
||||
};
|
||||
|
||||
static void slab_init(struct commit_slab *s)
|
||||
{
|
||||
memset(s, 0, sizeof(*s));
|
||||
}
|
||||
|
||||
static void slab_clear(struct commit_slab *s)
|
||||
{
|
||||
free(s->buf);
|
||||
slab_init(s);
|
||||
}
|
||||
|
||||
static inline int *slab_at(struct commit_slab *s, const struct commit *c)
|
||||
{
|
||||
if (s->alloc <= c->index) {
|
||||
int new_alloc = alloc_nr(s->alloc);
|
||||
if (new_alloc <= c->index)
|
||||
new_alloc = c->index + 1;
|
||||
|
||||
s->buf = xrealloc(s->buf, new_alloc * sizeof(*s->buf));
|
||||
memset(s->buf + s->alloc, 0, new_alloc - s->alloc);
|
||||
s->alloc = new_alloc;
|
||||
}
|
||||
return s->buf + c->index;
|
||||
}
|
||||
|
||||
/*
|
||||
* Performs an in-place topological sort on the list supplied.
|
||||
*/
|
||||
|
@ -505,15 +539,18 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
|
|||
struct commit_list *next, *orig = *list;
|
||||
struct commit_list *work, **insert;
|
||||
struct commit_list **pptr;
|
||||
struct commit_slab indegree;
|
||||
|
||||
if (!orig)
|
||||
return;
|
||||
*list = NULL;
|
||||
|
||||
slab_init(&indegree);
|
||||
|
||||
/* Mark them and clear the indegree */
|
||||
for (next = orig; next; next = next->next) {
|
||||
struct commit *commit = next->item;
|
||||
commit->indegree = 1;
|
||||
*slab_at(&indegree, commit) = 1;
|
||||
}
|
||||
|
||||
/* update the indegree */
|
||||
|
@ -521,9 +558,10 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
|
|||
struct commit_list * parents = next->item->parents;
|
||||
while (parents) {
|
||||
struct commit *parent = parents->item;
|
||||
int *pi = slab_at(&indegree, parent);
|
||||
|
||||
if (parent->indegree)
|
||||
parent->indegree++;
|
||||
if (*pi)
|
||||
(*pi)++;
|
||||
parents = parents->next;
|
||||
}
|
||||
}
|
||||
|
@ -540,7 +578,7 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
|
|||
for (next = orig; next; next = next->next) {
|
||||
struct commit *commit = next->item;
|
||||
|
||||
if (commit->indegree == 1)
|
||||
if (*slab_at(&indegree, commit) == 1)
|
||||
insert = &commit_list_insert(commit, insert)->next;
|
||||
}
|
||||
|
||||
|
@ -561,8 +599,9 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
|
|||
commit = work_item->item;
|
||||
for (parents = commit->parents; parents ; parents = parents->next) {
|
||||
struct commit *parent = parents->item;
|
||||
int *pi = slab_at(&indegree, parent);
|
||||
|
||||
if (!parent->indegree)
|
||||
if (!*pi)
|
||||
continue;
|
||||
|
||||
/*
|
||||
|
@ -570,7 +609,7 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
|
|||
* when all their children have been emitted thereby
|
||||
* guaranteeing topological order.
|
||||
*/
|
||||
if (--parent->indegree == 1) {
|
||||
if (--(*pi) == 1) {
|
||||
if (!lifo)
|
||||
commit_list_insert_by_date(parent, &work);
|
||||
else
|
||||
|
@ -581,10 +620,12 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
|
|||
* work_item is a commit all of whose children
|
||||
* have already been emitted. we can emit it now.
|
||||
*/
|
||||
commit->indegree = 0;
|
||||
*slab_at(&indegree, commit) = 0;
|
||||
*pptr = work_item;
|
||||
pptr = &work_item->next;
|
||||
}
|
||||
|
||||
slab_clear(&indegree);
|
||||
}
|
||||
|
||||
/* merge-base stuff */
|
||||
|
|
Loading…
Reference in a new issue