Name: _______________________________

CS 1550 – Quiz 1

Please answer the following questions.  You have 25 minutes to complete this quiz. (50 points)

1.) (10 points) List two things that would be part of a process table entry (PTE) but not a thread table entry.

Address space

Open files

Child processes

Signals & handlers

Accounting info

Global variables

2.) (10 points) What is the difference between mechanism and policy?

Mechanism

The way something is done (e.g., an algorithm)

Policy

The rules a particular mechanism should follow (i.e., the parameters of an algorithm)

3.) (20 points) List an advantage and a disadvantage of both User Threads and a Kernel threads.

	User Threading	Kernel Threading
Advantage	- Faster in theory to create - Don’t need explicit OS support - Can schedule with a different algo than the OS uses	- Don’t need to do explicit yielding (OS takes care of preemption) - May be fast in practice if good implementation
Disadvantage	- Must yield, no reliable mechanism for preemption - Must use nonblocking I/O calls otherwise whole process blocks	- in theory slower to create and manage due to system calls - Must use system-wide scheduling algorithm

4.) (10 points) Under Shortest Job First, if the following jobs (with indicated processing times) arrived at time zero, what would be the Average Turnaround Time and the Throughput? Show your work.

A (6)

B (4)

C (10)

D (8)

E (2)

Schedule is EBADC

Throughput is 5 jobs in 30 time units or 1/6

Turnaround time:

E: 2 – 0 = 2

B: 6-0=6

A: 12-0=12

D: 20-0=20

C: 30-0=30

Average Turnaround Time: 2+6+12+20+30 = 70/5