Systems Comprehensive Exam, Spring 2004
Tuesday, January 13, 2004
1 Instructions
This is a closed-book, closed-notes exam with a total of 75 points. You may not use any external source
for answering these questions. Please direct any questions about this exam to Professor Bridges, who may be
reached either in person in his office in 345G Farris, by phone at 277-3032, or by email at [email protected].
From 10:00am to 1:00pm, Professor Bridges will be available only by email or cell phone at 363-8798. Turn
your exam in to Professor Bridges or the front office by 5:00 PM MST on Tuesday, January 13, 2004. Exams
will not be accepted after this time except by prior arrangement with Professor Bridges.
Type or write your answers to the stated number of questions in each of the following three sections.
Make any reasonable assumptions necessary to answer the question, but be sure to state any assumptions
that you make.
2 Short Answer - Answer 3 of 4 (30 points)
Briefly answer 3 of the following 4 questions. Your answer should be no longer than one paragraph.
1. What is the alias problem in virtually indexed and tagged caches?
2. In a paged virtual memory system, what are the tradeoffs of choosing larger or smaller page sizes?
3. Shortest-job-first is a scheduling discipline that always runs the job with the least amount of compute
time remaining. What are the advantages and disadvantages of this scheduling discipline?
4. Compare and contrast the access guarantees provided by token-ring networks and ethernet networks.
3 Medium Answer - Answer 2 of 3 (20 points)
Provided detailed answers to two of the following three questions. Be sure to state any assumptions you
make and to fully justify your answers.
1. Consider an operating system’s network stack that processes headers on network packets prior to
transmitting them to the network or delivering them to the application (e.g., protocol stacks in UNIX
or the x-kernel.) Such network stacks can process packets either in their entirety, with each packet
traversing the entire set of layers and being delivered to the application before the next packet is
processed, or in batches with each layer processing several packets at a time. What tradeoff is involved
in this choice? Be sure to consider the cache performance of each approach.
2. Describe and illustrate the page table manipulations for sharing of data between two machines in a
distributed shared memory system and the state changes necessary when each machine first reads from
a shared page and later writes to a shared page.
3. (a) What is the difference between normal data and metadata in a file system?
(b) In what ways do these differences impact file system design?
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