Function should_pack_refs

refs/files-backend.c:1396–1456

}

static int should_pack_refs(struct files_ref_store *refs,
			    struct refs_optimize_opts *opts)
{
	struct ref_iterator *iter;
	size_t packed_size;
	size_t refcount = 0;
	size_t limit;
	int ret;

	if (!(opts->flags & REFS_OPTIMIZE_AUTO))
		return 1;

	ret = packed_refs_size(refs->packed_ref_store, &packed_size);
	if (ret < 0)
		die("cannot determine packed-refs size");

	/*
	 * Packing loose references into the packed-refs file scales with the
	 * number of references we're about to write. We thus decide whether we
	 * repack refs by weighing the current size of the packed-refs file
	 * against the number of loose references. This is done such that we do
	 * not repack too often on repositories with a huge number of
	 * references, where we can expect a lot of churn in the number of
	 * references.
	 *
	 * As a heuristic, we repack if the number of loose references in the
	 * repository exceeds `log2(nr_packed_refs) * 5`, where we estimate
	 * `nr_packed_refs = packed_size / 100`, which scales as following:
	 *
	 * - 1kB ~ 10 packed refs: 16 refs
	 * - 10kB ~ 100 packed refs: 33 refs
	 * - 100kB ~ 1k packed refs: 49 refs
	 * - 1MB ~ 10k packed refs: 66 refs
	 * - 10MB ~ 100k packed refs: 82 refs
	 * - 100MB ~ 1m packed refs: 99 refs
	 *
	 * We thus allow roughly 16 additional loose refs per factor of ten of
	 * packed refs. This heuristic may be tweaked in the future, but should
	 * serve as a sufficiently good first iteration.
	 */
	limit = log2u(packed_size / 100) * 5;
	if (limit < 16)
		limit = 16;

	iter = cache_ref_iterator_begin(get_loose_ref_cache(refs, 0), NULL,
					refs->base.repo, 0);
	while ((ret = ref_iterator_advance(iter)) == ITER_OK) {
		if (should_pack_ref(refs, &iter->ref, opts))
			refcount++;
		if (refcount >= limit) {
			ref_iterator_free(iter);
			return 1;
		}
	}

	if (ret != ITER_DONE)
		die("error while iterating over references");