1. CS533 - Concepts of Operating Systems
Class Discussion
CS533 - Concepts of Operating Systems

2. CS533 - Concepts of Operating Systems
Questions
Today’s OS kernel designs are based on a flawed assumption of low memory access latency
How has this affected their design?
What do the Tornado designers mean by locality?
Why isn’t a simple partitioning of data into per-processor components enough to ensure locality?
CS533 - Concepts of Operating Systems

3. CS533 - Concepts of Operating Systems
Questions
Does locality imply an inability to support global policies?
Why does an object oriented structure help to improve locality?
If objects represent OS abstractions such as processes and files
How much locality does this provide?
Is this enough?
How can you get more?
CS533 - Concepts of Operating Systems

4. CS533 - Concepts of Operating Systems
Questions
What is a clustered object?
What’s the upper limit on the degree of useful clustering (number of replicas)?
How could you use a clustered object approach to build a distributed counter?
Why are clustered objects better suited to larger granularity object types?
CS533 - Concepts of Operating Systems

5. CS533 - Concepts of Operating Systems
Questions
What is the difference between remote access and remote invocation?
How should reps of a clustered object communicate?
When might you want to migrate a rep?
How do you locate the right rep to communicate with?
How much does this cost?
What if a local rep doesn’t exist yet?
Why is it worth paying the extra cost of a level of indirection for invocation?
CS533 - Concepts of Operating Systems

6. CS533 - Concepts of Operating Systems
Questions
What is sequential consistency?
Why does it reduce performance on a multiprocessor?
What is a memory barrier, and why do you need them on modern CPU architectures?
Why do CPUs reorder instructions?
What implications does reordering have for synchronization primitives such as locks?
Does a programming model have to support sequential consistency in order to be intuitive?
CS533 - Concepts of Operating Systems