Incremental improvements to pack-objects logic

Incorporate feedback for incr. improvements to pack-objects

1 files changed, 86 insertions, 89 deletions

diff --git a/src/pack-objects.c b/src/pack-objects.c
index bb9b0eb88..eb76e05a2 100644
--- a/src/pack-objects.c
+++ b/src/pack-objects.c
@@ -30,6 +30,25 @@ struct unpacked {
 	unsigned int depth;
 };
 
+#ifdef GIT_THREADS
+
+#define GIT_PACKBUILDER__MUTEX_OP(pb, mtx, op) do { \
+		int result = git_mutex_##op(&(pb)->mtx); \
+		assert(!result); \
+		GIT_UNUSED(result); \
+	} while (0)
+
+#else
+
+#define GIT_PACKBUILDER__MUTEX_OP(pb,mtx,op) GIT_UNUSED(pb)
+
+#endif /* GIT_THREADS */
+
+#define git_packbuilder__cache_lock(pb) GIT_PACKBUILDER__MUTEX_OP(pb, cache_mutex, lock)
+#define git_packbuilder__cache_unlock(pb) GIT_PACKBUILDER__MUTEX_OP(pb, cache_mutex, unlock)
+#define git_packbuilder__progress_lock(pb) GIT_PACKBUILDER__MUTEX_OP(pb, progress_mutex, lock)
+#define git_packbuilder__progress_unlock(pb) GIT_PACKBUILDER__MUTEX_OP(pb, progress_mutex, unlock)
+
 static unsigned name_hash(const char *name)
 {
 	unsigned c, hash = 0;
@@ -84,29 +103,37 @@ int git_packbuilder_new(git_packbuilder **out, git_repository *repo)
 
 	*out = NULL;
 
-	pb = git__malloc(sizeof(*pb));
+	pb = git__calloc(sizeof(*pb), 1);
 	GITERR_CHECK_ALLOC(pb);
 
-	memset(pb, 0x0, sizeof(*pb));
-
 	pb->object_ix = git_oidmap_alloc();
-	GITERR_CHECK_ALLOC(pb->object_ix);
+
+	if (!pb->object_ix)
+		goto on_error;
 
 	pb->repo = repo;
 	pb->nr_threads = 1; /* do not spawn any thread by default */
 	pb->ctx = git_hash_new_ctx();
 
-	if (git_repository_odb(&pb->odb, repo) < 0)
+	if (!pb->ctx ||
+		git_repository_odb(&pb->odb, repo) < 0 ||
+		packbuilder_config(pb) < 0)
 		goto on_error;
 
-	if (packbuilder_config(pb) < 0)
+#ifdef GIT_THREADS
+
+	if (git_mutex_init(&pb->cache_mutex) ||
+		git_mutex_init(&pb->progress_mutex) ||
+		git_cond_init(&pb->progress_cond))
 		goto on_error;
 
+#endif
+
 	*out = pb;
 	return 0;
 
 on_error:
-	git__free(pb);
+	git_packbuilder_free(pb);
 	return -1;
 }
 
@@ -134,12 +161,13 @@ int git_packbuilder_insert(git_packbuilder *pb, const git_oid *oid,
 			   const char *name)
 {
 	git_pobject *po;
-	git_odb_object *obj;
 	khiter_t pos;
 	int ret;
 
 	assert(pb && oid);
 
+	/* If the object already exists in the hash table, then we don't
+	 * have any work to do */
 	pos = kh_get(oid, pb->object_ix, oid);
 	if (pos != kh_end(pb->object_ix))
 		return 0;
@@ -152,16 +180,14 @@ int git_packbuilder_insert(git_packbuilder *pb, const git_oid *oid,
 		rehash(pb);
 	}
 
-	if (git_odb_read(&obj, pb->odb, oid) < 0)
-		return -1;
-
-	po = pb->object_list + pb->nr_objects++;
+	po = pb->object_list + pb->nr_objects;
 	memset(po, 0x0, sizeof(*po));
 
+	if (git_odb_read_header(&po->size, &po->type, pb->odb, oid) < 0)
+		return -1;
+
+	pb->nr_objects++;
 	git_oid_cpy(&po->id, oid);
-	po->type = git_odb_object_type(obj);
-	po->size = git_odb_object_size(obj);
-	git_odb_object_free(obj);
 	po->hash = name_hash(name);
 
 	pos = kh_put(oid, pb->object_ix, &po->id, &ret);
@@ -653,24 +679,6 @@ static int delta_cacheable(git_packbuilder *pb, unsigned long src_size,
 	return 0;
 }
 
-#ifdef GIT_THREADS
-static git_mutex cache_mutex;
-#define cache_lock()		git_mutex_lock(&cache_mutex);
-#define cache_unlock()		git_mutex_unlock(&cache_mutex);
-
-static git_mutex progress_mutex;
-#define progress_lock()		git_mutex_lock(&progress_mutex);
-#define progress_unlock()	git_mutex_unlock(&progress_mutex);
-
-static git_cond progress_cond;
-#else
-
-#define cache_lock()		(void)0;
-#define cache_unlock()		(void)0;
-#define progress_lock()		(void)0;
-#define progress_unlock()	(void)0;
-#endif
-
 static int try_delta(git_packbuilder *pb, struct unpacked *trg,
 		     struct unpacked *src, unsigned int max_depth,
 		     unsigned long *mem_usage, int *ret)
@@ -780,7 +788,7 @@ static int try_delta(git_packbuilder *pb, struct unpacked *trg,
 		}
 	}
 
-	cache_lock();
+	git_packbuilder__cache_lock(pb);
 	if (trg_object->delta_data) {
 		git__free(trg_object->delta_data);
 		pb->delta_cache_size -= trg_object->delta_size;
@@ -788,13 +796,13 @@ static int try_delta(git_packbuilder *pb, struct unpacked *trg,
 	}
 	if (delta_cacheable(pb, src_size, trg_size, delta_size)) {
 		pb->delta_cache_size += delta_size;
-		cache_unlock();
+		git_packbuilder__cache_unlock(pb);
 
 		trg_object->delta_data = git__realloc(delta_buf, delta_size);
 		GITERR_CHECK_ALLOC(trg_object->delta_data);
 	} else {
 		/* create delta when writing the pack */
-		cache_unlock();
+		git_packbuilder__cache_unlock(pb);
 		git__free(delta_buf);
 	}
 
@@ -855,15 +863,15 @@ static int find_deltas(git_packbuilder *pb, git_pobject **list,
 		unsigned int max_depth;
 		int j, best_base = -1;
 
-		progress_lock();
+		git_packbuilder__progress_lock(pb);
 		if (!*list_size) {
-			progress_unlock();
+			git_packbuilder__progress_unlock(pb);
 			break;
 		}
 
 		po = *list++;
 		(*list_size)--;
-		progress_unlock();
+		git_packbuilder__progress_unlock(pb);
 
 		mem_usage -= free_unpacked(n);
 		n->object = po;
@@ -935,10 +943,10 @@ static int find_deltas(git_packbuilder *pb, git_pobject **list,
 			po->z_delta_size = zbuf.size;
 			git_buf_clear(&zbuf);
 
-			cache_lock();
+			git_packbuilder__cache_lock(pb);
 			pb->delta_cache_size -= po->delta_size;
 			pb->delta_cache_size += po->z_delta_size;
-			cache_unlock();
+			git_packbuilder__cache_unlock(pb);
 		}
 
 		/*
@@ -1006,22 +1014,6 @@ struct thread_params {
 	int data_ready;
 };
 
-static void init_threaded_search(void)
-{
-	git_mutex_init(&cache_mutex);
-	git_mutex_init(&progress_mutex);
-
-	git_cond_init(&progress_cond);
-}
-
-static void cleanup_threaded_search(void)
-{
-	git_cond_free(&progress_cond);
-
-	git_mutex_free(&cache_mutex);
-	git_mutex_free(&progress_mutex);
-}
-
 static void *threaded_find_deltas(void *arg)
 {
 	struct thread_params *me = arg;
@@ -1032,10 +1024,10 @@ static void *threaded_find_deltas(void *arg)
 			; /* TODO */
 		}
 
-		progress_lock();
+		git_packbuilder__progress_lock(me->pb);
 		me->working = 0;
-		git_cond_signal(&progress_cond);
-		progress_unlock();
+		git_cond_signal(&me->pb->progress_cond);
+		git_packbuilder__progress_unlock(me->pb);
 
 		/*
 		 * We must not set ->data_ready before we wait on the
@@ -1062,13 +1054,11 @@ static int ll_find_deltas(git_packbuilder *pb, git_pobject **list,
 	struct thread_params *p;
 	int i, ret, active_threads = 0;
 
-	init_threaded_search();
-
 	if (!pb->nr_threads)
 		pb->nr_threads = git_online_cpus();
+
 	if (pb->nr_threads <= 1) {
 		find_deltas(pb, list, &list_size, window, depth);
-		cleanup_threaded_search();
 		return 0;
 	}
 
@@ -1133,20 +1123,28 @@ static int ll_find_deltas(git_packbuilder *pb, git_pobject **list,
 		struct thread_params *victim = NULL;
 		unsigned sub_size = 0;
 
-		progress_lock();
+		/* Start by locating a thread that has transitioned its
+		 * 'working' flag from 1 -> 0. This indicates that it is
+		 * ready to receive more work using our work-stealing
+		 * algorithm. */
+		git_packbuilder__progress_lock(pb);
 		for (;;) {
 			for (i = 0; !target && i < pb->nr_threads; i++)
 				if (!p[i].working)
 					target = &p[i];
 			if (target)
 				break;
-			git_cond_wait(&progress_cond, &progress_mutex);
+			git_cond_wait(&pb->progress_cond, &pb->progress_mutex);
 		}
 
+		/* At this point we hold the progress lock and have located
+		 * a thread to receive more work. We still need to locate a
+		 * thread from which to steal work (the victim). */
 		for (i = 0; i < pb->nr_threads; i++)
 			if (p[i].remaining > 2*window &&
 			    (!victim || victim->remaining < p[i].remaining))
 				victim = &p[i];
+
 		if (victim) {
 			sub_size = victim->remaining / 2;
 			list = victim->list + victim->list_size - sub_size;
@@ -1172,7 +1170,7 @@ static int ll_find_deltas(git_packbuilder *pb, git_pobject **list,
 		target->list_size = sub_size;
 		target->remaining = sub_size;
 		target->working = 1;
-		progress_unlock();
+		git_packbuilder__progress_unlock(pb);
 
 		git_mutex_lock(&target->mutex);
 		target->data_ready = 1;
@@ -1187,7 +1185,6 @@ static int ll_find_deltas(git_packbuilder *pb, git_pobject **list,
 		}
 	}
 
-	cleanup_threaded_search();
 	git__free(p);
 	return 0;
 }
@@ -1196,18 +1193,6 @@ static int ll_find_deltas(git_packbuilder *pb, git_pobject **list,
 #define ll_find_deltas(pb, l, ls, w, d) find_deltas(pb, l, &ls, w, d)
 #endif
 
-static void get_object_details(git_packbuilder *pb)
-{
-	git_pobject *po;
-	unsigned int i;
-
-	for (i = 0; i < pb->nr_objects; ++i) {
-		po = &pb->object_list[i];
-		if (pb->big_file_threshold < po->size)
-			po->no_try_delta = 1;
-	}
-}
-
 static int prepare_pack(git_packbuilder *pb)
 {
 	git_pobject **delta_list;
@@ -1216,18 +1201,14 @@ static int prepare_pack(git_packbuilder *pb)
 	if (pb->nr_objects == 0 || pb->done)
 		return 0; /* nothing to do */
 
-	get_object_details(pb);
-
 	delta_list = git__malloc(pb->nr_objects * sizeof(*delta_list));
 	GITERR_CHECK_ALLOC(delta_list);
 
 	for (i = 0; i < pb->nr_objects; ++i) {
 		git_pobject *po = pb->object_list + i;
 
-		if (po->size < 50)
-			continue;
-
-		if (po->no_try_delta)
+		/* Make sure the item is within our size limits */
+		if (po->size < 50 || po->size > pb->big_file_threshold)
 			continue;
 
 		delta_list[n++] = po;
@@ -1310,9 +1291,25 @@ void git_packbuilder_free(git_packbuilder *pb)
 	if (pb == NULL)
 		return;
 
-	git_odb_free(pb->odb);
-	git_hash_free_ctx(pb->ctx);
-	git_oidmap_free(pb->object_ix);
-	git__free(pb->object_list);
+#ifdef GIT_THREADS
+
+	git_mutex_free(&pb->cache_mutex);
+	git_mutex_free(&pb->progress_mutex);
+	git_cond_free(&pb->progress_cond);
+
+#endif
+
+	if (pb->odb)
+		git_odb_free(pb->odb);
+
+	if (pb->ctx)
+		git_hash_free_ctx(pb->ctx);
+
+	if (pb->object_ix)
+		git_oidmap_free(pb->object_ix);
+
+	if (pb->object_list)
+		git__free(pb->object_list);
+
 	git__free(pb);
 }