Understanding and managing the propagation of states in operating systems has become an intractable problem due to their sheer size and complexity. Despite modularization efforts, it remains a significant barrier to many contemporary computing goals: process migration, fault isolation and tolerance, live update, software virtualization, and more. Though many previous OS research endeavors have achieved these goals through ad-hoc, tedious methods, we argue that they have missed the underlying reason why these goals are so challenging: state spill.