public function add_global_groups( $groups ) {
                $groups = (array) $groups;

                // Filter global groups
                $groups              = array_diff_key( $groups, WP_REDIS_IGNORE_GLOBAL_GROUPS );

                $groups              = array_fill_keys( $groups, true );
                $this->global_groups = array_merge( $this->global_groups, $groups );
        }

wp> print_r($GLOBALS['wp_object_cache']->global_groups)
Array
(
    [site-transient] => 1
    [site-options] => 1
    [blog-lookup] => 1
    [blog-details] => 1
    [site-details] => 1
    [rss] => 1
    [global-posts] => 1
    [blog-id-cache] => 1
    [networks] => 1
    [sites] => 1
    [blog_meta] => 1
)