One Minute Evaluations for 5-7 October 2004

CS 438-505 - Operating Systems Concepts

• Topic: We talked about how the communication between processes is expensive because it crosses the OS boundary.

  Question: You said you pass a copy of the data when you communicate, but can it just be a pointer?

  One minute response: Generally, no. The data at location 100 in one process has no relation to the data at location 100 in another process, and the pointer (address) in both processes look the same.

• Question: How do I view a semaphore? Is it a real data [?] somewhere? Do message queues necessarily enforce msg passing between two processors?

  One minute response: A semaphore is an boolean flag with the operations put and take. Put set the flag to true and take blocks until the flag is true and then sets it to false. It depends on how message queues are implemented, but I would think so; there are far more efficient ways for a process to send a message to itself than to use a message queue.

• Topic: We just spoke about synchronization in general. Will we talk about specifics like critical sections, semaphores, and mutexes?

  Question: De we really need scheduling in the first assignment?

  One minute response: Whenever you have more than one non-OS process, you need scheduling. Most of the batch disks create more than one non-OS process.

• Topic: We learned about concurrency and time sharing.

  Question: If sockets are so expensive, why do we use them?

  One minute response: They're ported widely; there's a large base of socket expertise to draw on; the alternatives are worse.

• Topic: Talked about concurrency, IPC, multischeduling, context switching.

• Topic: This week we talked about coordination and concurrency. We talked about the architecture of concurrency and we got into how threads need coordination if they run in concurrency to be effective.

• Topic: Concurrency, coordination, data sharing, control sharing.

  Question: None right now.

• Topic: We talked about scheduling methods and intra- and inter-process communication.

  Question: In past semesters, what percentage of OS students successfully wrote properly functioning operating systems?

  One minute response: For the graduate students I'd guess about half; for the undergraduates I'd guess less than a quarter.

• Topic: Process sharing, control and data sharing.

  Question: Are the other assignments smaller?

  One minute response: The memory-management is, the file-management assignment is definitely not; the device-management assignment is not and usually requires re-writing (These are my experiences; your experiences may be different). You can look at the assignments from past courses for examples.

• Topic: Learned: concurrency, types of concurrency among processes.

  Question: In class you mentioned Doom. I was wondering if you play video games in your spare time.

  One minute response: Nope.

This page last modified on 16 July 2003.