cse4600 Exam 2

Question 1

What does PF stand for and what does it do?

Answer 1

Priority Function; The decision for which process will be allowed to execute

Question 2

What does AR stand for and what does it do?

Answer 2

Arbitration Function; When two processes with equal priority are too be scheduled

Question 3

What does DM stand for and what does it do?

Answer 3

Dynamic priority Measures; Parameters that change over time

Question 4

Name some system measures that may determine priority level

Answer 4

external priority
total service time
deadline
real-time in the system
memory requirements

Question 5

What is turnaround time

Answer 5

Total time between the submission of the process for execution and the return of the complete output

Question 6

What is waiting time

Answer 6

amount of time a job is sitting ideal before the process is used

Question 7

First in First out - Pros and Cons

Answer 7

Pro
- Easy to implement
- Ignores service time
Cons
- Not a great performer

Question 8

First in First out PF

Answer 8

P = r, where r is the amount of real time

Question 9

First in First out DM

Answer 9

Non - Preemptive

Question 10

First in First out AR

Answer 10

random choice among processes arriving at exactly the same time

Question 11

Shortest Job First PF

Answer 11

P = -t, where t is the total service time

Question 12

Shortest Job First DM

Answer 12

Non - Preemptive

Question 13

Shortest Job First AR

Answer 13

either chronological or random among processes with same service time

Question 14

Shortest Remaining Time PF

Answer 14

P = - (t - a), where t-a is the remaining time

Question 15

Shortest Remaining Time DM

Answer 15

Preemptive

Question 16

Shortest Remaining Time AR

Answer 16

chronological or random among processes with same service time

Question 17

Round Robin PF

Answer 17

P = 0, all processes have the same priority

Question 18

Round Robin DM

Answer 18

preemptive quantum oriented

Question 19

Round Robin AR

Answer 19

cyclic

Question 20

Multilevel Priority PF

Answer 20

P = e

Question 21

Multilevel Priority DM

Answer 21

preemptive if newly arriving process has a higher priority

within each priority queue, scheduling may be preemptive RR or non-preemptive FIFO

Question 22

Multilevel Priority AR

Answer 22

cyclic if RR, random/chronological if FIFO

Question 23

Multilevel Feedback PF

Answer 23

function of attained service time with different implementations possible

Question 24

Multilevel Feedback DM

Answer 24

preemptive or non-preemptive; processes in the same level may use RR or FIFO

Question 25

Multilevel Feedback AR

Answer 25

cyclic or random/chronological

Question 26

Rate Monotonic PF

Answer 26

P = -d, where d is a fixed period of time that process needs to use the cpu

Question 27

Rate Monotonic DM

Answer 27

preemptive

Question 28

Rate Monotonic AR

Answer 28

random or chronological

Question 29

Earliest Deadline First PF

Answer 29

P = -(d-r%d), where r is the time since process first entered the system d is its period

Question 30

Earliest Deadline First DM

Answer 30

preemptive and dynamic

Question 31

Earliest Deadline First AR

Answer 31

random or chronological

Question 32

What is a time quantum

Answer 32

amount of timeshare (timeslice) given to each process, interrupting the job if it is not completed by then

Question 33

What is throughput

Answer 33

the number of processes that are completed per time unit

Question 34

What is response time

Answer 34

the time it takes to start responding, from the submission of the request until the first response is produced

Question 35

What is turnaround time

Answer 35

from the time of submission of a process to the time of completion

Question 36

What is waiting time

Answer 36

the sum of the periods spent waiting in the ready queue

Question 37

What is burst time

Answer 37

the amount of time the process uses the processor before it is no longer ready

Question 38

What is priority inversion

Answer 38

when a low priority process blocks a high priority process from executing because the low priority process is being preempted by a medium process

Question 39

Shortest Job First - Pro

Answer 39

provably optimal, results in minimum average waiting time

Question 40

Round Robin - Pro and Con

Answer 40

Pro - better response than SJF Con - higher average turnaround

Question 41

What is the equation for schedulability

Answer 41

n ( 2^1/n - 1 )

Question 42

Primary use for Earliest Deadline First?

Answer 42

For real-time systems

Question 43

When is a schedule feasible?

Answer 43

When all deadlines are satisfied

Question 44

What is a method optimal?

Answer 44

If it always produces a feasible schedule if one exists

Question 45

Rate Monotonic - Pros

Answer 45

- Simpler implementation | - Predicability for the highest priority

Question 46

Earliest Deadline First - Pros

Answer 46

- Full processor utilizaiton | - Misbehavior during overload conditions

Question 47

For Eventcount, what does await(E, v) do?

Answer 47

suspends the calling process if E < v; otherwise it allows the process to proceed

Question 48

For Eventcount, what does advance(E) do?

Answer 48

eventcount value E is incremented and next process is admitted for service

Question 49

For Eventcount, what does read(E) do?

Answer 49

inspects the current value of E

Question 50

What does a monitors condition variable wait() do?

Answer 50

causes the executing process to be suspended on the queue

Question 51

What does a monitors condition variable signal() do?

Answer 51

wakes up a process thats waiting on CV

Question 52

What does a monitors condition variable queue() do?

Answer 52

true if queue is not empty, false if no process is waiting in the queue

Question 53

For Mesa Semantics the thread that signals

Answer 53

keeps the lock

Question 54

For Mesa Semantics the waiting thread

Answer 54

waits for the lock

Question 55

For Hoare Semantics the thread that signals

Answer 55

gives up the lock and the waiting thread gets the lock

Question 56

T/F: Hoare uses if rather than while

Answer 56

True

Question 57

T/F: Mesa uses if rather than while

Answer 57

False

Question 58

T/F: Monitors provide mutual exclusion between all procedures between shared data

Answer 58

True

Question 59

For a producer/consumer problem why is P(mutex) P(full) incorrect?

Answer 59

Because it will set Full variable and mutex variable to -1 and both Producer and Consumer will wait

Question 60

What is a weak reader

Answer 60

an arriving writer waits until there are no more active readers

Question 61

What is a strong reader

Answer 61

waiting reader has priority over a waiting writer

Question 62

What is writer priority?

Answer 62

an arriving reader waits until there are no more active or waiting writers

Question 63

Counting semaphores are used

Answer 63

to manage limited resources and corresponding access to them

Question 64

Binary semaphores are usually used

Answer 64

to facilitate mutual exclusion

Question 65

P(s) =

Answer 65

wait(s) = down(s)

Question 66

V(s) =

Answer 66

signal(s) = up(s)