Tutorial Week 6

Questions

Q1: What do the terms I/O bound and CPU bound mean when used to describe a process (or thread)?

Q2: What is the difference between cooperative and pre-emptive multitasking?

Q3: Consider the multilevel feedback queue scheduling algorithm used in traditional Unix systems. It is designed to favour IO bound over CPU bound processes. How is this achieved? How does it make sure that low priority, CPU bound background jobs do not suffer starvation?

Note: Unix uses low values to denote high priority and vice versa, 'high' and 'low' in the above text does not refer to the Unix priority value.

Q4: Why would a hypothetical OS always schedule a thread in the same address space over a thread in a different address space? Is this a good idea?

Q5: Why would a round robin scheduler NOT use a very short time slice to provide good responsive application behaviour?

Q6: Consider 3 periodic tasks with execution profiles shown below. Draw scheduling diagram for a rate monotonic and a earliest deadline first schedule.

Process Arrival Time Execution Time Deadline
A (1) 0 10 20
A (2) 20 10 40
. . .
B (1) 0 10 50
B (2) 50 10 100
. . .
C (1) 0 15 50
C (2) 50 15 100