From 96c4f4a370591b4796628abe18f27f0133b21954 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Tue, 9 Apr 2013 02:52:56 -0400 Subject: [PATCH] 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 --- commit.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++--------- commit.h | 2 +- 2 files changed, 51 insertions(+), 10 deletions(-) diff --git a/commit.c b/commit.c index 1a41757ee3..9365e3b34a 100644 --- a/commit.c +++ b/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 */ diff --git a/commit.h b/commit.h index 252c7f871c..70e749d69f 100644 --- a/commit.h +++ b/commit.h @@ -14,7 +14,7 @@ struct commit_list { struct commit { struct object object; void *util; - unsigned int indegree; + unsigned int index; unsigned long date; struct commit_list *parents; struct tree *tree; -- 2.43.2