1. CS533 Concepts of Operating Systems Class 5 Event-Based Systems

2. CS533 - Concepts of Operating Systems 2 Questions  Why does thread programming de-emphasize I/O?  What do interactive applications, network services, and operating system kernels have in common?  How does event-based programming relate to interrupt handling?  Where is the boundary between interrupt handling and scheduled thread execution? o What are the implications of mixing these models?

3. CS533 - Concepts of Operating Systems 3 Questions  What is the problem with making resource allocation decisions statically? o What is the Slashdot effect?  Why is massive concurrency not a good match for multi-threading? o Is web service embarrassingly parallel?  What transparency is imposed (ie., what is hidden?) by the thread-per request model? o Why does it hurt? o Why does the event handling model help?

4. CS533 - Concepts of Operating Systems 4 Questions  How can resources be scheduled in event-based programming?  What is the problem with event handlers blocking or performing long-lived computation?

5. CS533 - Concepts of Operating Systems 5 Questions  What is a thread pool?  Why do the following techniques help during heavy load? o Thread pool resizing o Event batching o Adaptive load shedding  Why does pipeline parallelism scale well? o Thread per stage vs thread per request  What does it mean for a service to be “well conditioned”?

6. CS533 - Concepts of Operating Systems 6 Questions  Do Ousterhout and Welsh contradict each other? o What is hard about programming threads? o What is easy about programming threads? o What is hard about programming events? o What is easy about programming events?

7. CS533 - Concepts of Operating Systems 7 Reminder  Class 6 presenters o Discuss your presentation plans with me ahead of time o Mail me the final version of your slides BEFORE the class