User-Level Device Drivers: Achieved Performance

Running device drivers as unprivileged user-level code, encapsulatedinto their own process, has often been proposed as a technique forincreasing system robustness. However, in the past, systems based onuser-level drivers have generally exhibited poor I/O performance.Consequently, user-level device drivers have never caught on to anysignificant degree. In this paper we demonstrate that it is possible tobuild systems which employ user-level device drivers, withoutsignificant performance degradation, even for high-bandwidth devicessuch as Gigabit Ethernet.