1. CS533 Concepts of Operating Systems Class 8 System Structuring using Layers

2. CS533 - Concepts of Operating Systems 2 Questions  Why is performance a problem in process-per-layer or even thread-per-layer mappings of specifications to implementations? o What are the costs of crossing layer boundaries?  If data is not passed across layer boundaries in buffers, how is it passed in Swift? o How is inter-task communication within a multi-task module implemented in Swift?

3. CS533 - Concepts of Operating Systems 3 Questions  What do “up” and “down” mean in the context of Swift upcalls and downcalls? o Why is arming required in upcalling, but not in downcalling? o Why is upcalling more perilous than downcalling?  When is it better to use upcalls than downcalls?  Should you always pass data among tasks on the stack? o How do you decide what work must be done immediately and what to queue for later? If you queue it for later, where should you store the state?

4. CS533 - Concepts of Operating Systems 4 Questions  Are upcalls part of a thread-based or event-based programming model?  Is arming stack-ripping? o Does it leave state for a future call-back?  How does Swift implement protection?  What safety rules (conventions) are used in Swift?