Session Data lost when redirect to a view

I have setting a session in my controller  by using

PHP Code:

           $this->load->model('user_m');
            $ui = $this->user_m->login($username, $password);
            if ($ui) {
                
                $this->load->library('session');
                $this->session->set_userdata('userinfo',$ui); 


But when i redirect it to my view.... it gives nothing... 
1) where's the session data goes.
2)How to get the session data in my view