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Due: Thursday, March 24, in class
Answer the following questions. Your answers should be typed (except for the Gantt diagrams, which you may draw by hand).Question 1. Briefly define each of these terms (one or two sentences each):
Question 2. Suppose that the OS needs to choose and dispatch another process to execute and that, at this time, there are processes in both the ready state and the ready-suspend state. Furthermore, suppose that at least one process in the ready-suspend state has higher scheduling priority than any of the processes in the ready state. Two extreme policies for deciding which process to execute are: (1) Always dispatch a process in the ready state. (2) Always dispatch the highest-priority process. What is a concern with each of these two policies? Is there an intermediate policy that tries to balance these concerns?
Question 3. Thread questions:
Question 4. Suppose the following jobs are to be executed in a uniprocessor system.
Job Number | Arrival Time | Service Time |
1 | 0 | 4 |
2 | 1 | 8 |
3 | 3 | 2 |
4 | 10 | 6 |
5 | 12 | 5 |
Assume the overhead of context switching is one time unit. For each of the following scheduling methods, give (i) a timing chart (Gantt diagram) to illustrate the execution sequence, (ii) the average job turnaround time, (iii) the normalized turnaround time for each job, and (iv) the CPU efficiency.
Question 5. What type of process is generally favored by a multilevel feedback queueing scheduler, a CPU-bound process or an I/O-bound process? Briefly explain why.
Question 6. Consider a variant of the RR scheduling algorithm where the entries in the ready queue are pointers to the PCBs.
Question 7. What would happen if you executed the following piece of code:
main() { for(;;) fork(); }
Note: Don't try this on a real machine.
Completed homework:
Constance Royden--croyden@mathcs.holycross.edu
Computer Science 346--Operating Systems
Date Created: January 9, 2004
Last Modified: March 2, 2011
Page Expires: January 8, 2012