CS533 Concepts of Operating Systems Class 12

1. CS533 Concepts of Operating SystemsClass 12 Micro-kernels (or Extensibility via Hardware-Based Protection)

2. Questions • What is the motivation for modular operating systems? • Does this imply modules with hardware protection? • .. and what do I mean by hardware protection for modules? • What is the motivation for using hardware protection at module boundaries? • Does this imply message passing across module boundaries? • … what other alternatives do you have? • What is the motivation for using message-passing for inter-module communication? CS533 - Concepts of Operating Systems

3. Questions • What is the structure of a pure emulation library-based OS above a micro-kernel? • How are system calls handled? • What is the structure of a single-server based OS above a micro-kernel? • How are system calls handled? • What is the structure of a multi-server based OS above a micro-kernel? • How are system calls handled? CS533 - Concepts of Operating Systems

4. Questions • What are the main sources of overhead in micro-kernel based OSs compared to monolithic OSs? • How does L4 address these overheads? • Do these optimizations completely solve the problem? • What is the difference between L4 IPC and a protected control transfer (PCT)? • Would you expect a lot of difference in performance following extreme optimization of both? • What minimal abstractions should a kernel provide? CS533 - Concepts of Operating Systems

5. Questions • What is extensibility and how does micro-kernel-based OS structure help? • What other approaches are there? CS533 - Concepts of Operating Systems

6. Reminder • Take a look at the Liedtke paper from SOSP’93 • Presenters, start working your talk early! • Don’t leave it to the last minute! You can’t expect to do an adequate job if you do it the night before. • Send me a draft of your slides early enough that I have some time to work with you CS533 - Concepts of Operating Systems