Page 113 - DCAP103_Principle of operating system

Principles of Operating Systems

Notes 7. Consider multi-processor system and a multi-threaded program written using the many-
to-many threading model. Let the number of user-level threads in the program be more
than the number of processors in the system. Discuss the performance implications of the
following scenarios.

(a) The number of kernel threads allocated to the program is less than the number of
processors.
(b) The number of kernel threads allocated to the program is equal to the number of
processors.
(c) The number of kernel threads allocated to the program is greater than the number of
processors but less than the number of user level threads.
8. Write a multi-threaded Java, Pthreads, or Win32 program that outputs prime numbers.
This program should work as follows: The user will run the program and will enter a
number on the command line. The program will then create a separate thread that outputs
all the prime numbers less than or equal to the number entered by the user.
9. Why is it important for the scheduler to distinguish I/O-bound programs from CPU-bound
programs?

10. Discuss how the following pairs of scheduling criteria conflict in certain settings.
(a) CPU utilization and response time
(b) Average turnaround time and maximum waiting time

(c) I/O device utilization and CPU utilization
11. Which of the following scheduling algorithms could result in starvation?
(a) First-come, first-served
(b) Shortest job first

(c) Round robin
12. Consider a system implementing multilevel queue scheduling. What strategy can a
computer user employ to maximize the amount of CPU time allocated to the user’s process?
13. Explain the differences in the degree to which the following scheduling algorithms
discriminate in favor of short processes:
(a) FCFS
(b) RR

(c) Multilevel feedback queues
14. Using the Windows XP scheduling algorithm, what is the numeric priority of a thread for
the following scenarios?

(a) A thread in the REALTIME PRIORITY CLASS with a relative priority of HIGHEST.
(b) A thread in the NORMAL PRIORITY CLASS with a relative priority of NORMAL.
(c) A thread in the HIGH PRIORITY CLASS with a relative priority of ABOVE NORMAL.

15. Consider the scheduling algorithm in the Solaris operating system for time sharing threads:
(a) What is the time quantum (in milliseconds) for a thread with priority 10? With priority
55?

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