CS 162, Spring 1990
Midterm #2
Professor David Anderson
Problem #1 (10 points)
true/false
-I/O buffering can increase CPU utilization.
-The two "sides" of a UNIX pseudo-tty are equivelent.
-Shortest CPU burst first process scheduling minimizes average turnaround time.
-Sun NFS client caches are always consistent
-Data can flow both up and down between adjacent protocol layers.
Problem #2 (10 points)
a) List three input functions and one output function of the BSD UNIX line discipline in cooked mode
b) Would system performance increase or decrease if line disciplines were moved from the kernel to the user
level? Explain.
Problem #3 (10 points)
a) What does it mean to say that access to a resource is "fair"?
b) What is "aging"? Under what circumstances does aging provide fairness and why?
c) The "fair share scheduler" used in some versions of UNIX provides a different kind of fairness. Describe
as precisely as you can this notion of "fairness"?
d) Describe, in words or in pseudocode, what the sending side of RMP does to deliver a client message.
When should the client call (to send the message) return?
e) Describe, in words or in pseudocode, what the receiving side of RMP does to handle an incoming
datagram.
f) Is RMP appropriate for wide-area networks? Explain.
Problem #4 (15 points)
Not available
Problem #5 (15 points)
Not available.
Problem #6 (15 points)
Acne's computers use a BSD UNIX-based operating system. Noah Tall has complained that the following
pair of calls run slower than they should:
fd = open("/a/b", O_RDONLY, 0);
read(fd, buf, l);
CS162 Spring 1990, MT2
CS 162, Spring 1990 Midterm #2 Professor David Anderson 1
