Experiences in Teaching an Educational User-Level Operating Systems Implementation Project

The importance of a comprehensive implementation component for undergraduate Operating Systems (OS) courses cannot be understated. Students not only develop deep insight and understanding of OS fundamentals, but they also learn key software engineering skills that only a large development project, such as implementing an OS, can teach. There are clear benefits to traditional OS projects where students program or alter real (Linux) kernel source or extend educational OS implementations; however, in our experience, bootstrapping such a project is a huge undertaking that may not be accessible in many classrooms. In this paper, we describe a different approach to the OS implementation assignment: A user-level Operating System simulation based on UNIX preemptive signaling and threading constructs called ucontext. We believe that this variation of the implementation assignment provides many of the same educational benefits as traditional low-level projects without many of the expensive start-up costs. This project has been taught for a number of years at the University of Pennsylvania and was recently overhauled for the Fall 2011 semester. This paper describes the current version of the project and our experiences teaching it to a class of 54 students.