NPTEL Real-Time Systems Assignment 3 Answers 2022

1 point
A table-driven scheduler has which of the following characteristics?a. Static

b. Dynamic

c. Offline

d. Online

e. Event-driven

f. Preemptive

g. Compact

h. Efficient

i. Clock-driven

Ans – A, B, C, F, H
1 point
In a foreground-background scheduler, a background task requiring 900milliseconds is to be run. A foreground task T1 with execution time 8milliseconds and period of 100 millisecond is also executed. Assuming a context switch time of 1millisecond, what will be the completion time of the background task? Assume all tasks have zero phasing.a. 900 milliseconds

b. 950 milliseconds

c. 1000 milliseconds

d. 1200 milliseconds

e. 1500 milliseconds

Ans – A, e,

1 point
Which one of the following defines the scheduling points of a cyclic scheduler?

a. Frame boundary

b. Major cycle

c. Job arrival

d. Job completion

e. Both job arrival and job completion

Ans – d, e
1 point
Suppose a cyclic scheduler is used to schedule a set of periodic real-time tasks {Ti}. The execution
time, period, and deadline of a task Ti is given by <ei,Pi,di>. Which one of the following expressions
correctly expresses the minimum separation of the arrival of a task Ti from a frame boundary?a. GCD(F,pi)

b. 2×GCD(F,pi)

c. 2×F-GCD(F,pi)

d. 2×F-GCD(F,di)

e. 2×F-GCD(F,ei)

Ans – D
1 point
Suppose a cyclic scheduler is used to schedule a set of three periodic real-time tasks {T1, T2, T3}.
The execution time, period, and deadline of a task Ti is given by <ei,Pi,di>. A chosen frame size
must satisfy which of the following?a. F ≥ max(e1,e2,e3)

b. (LCM(P1,P2,P3)/F)×F= LCM(P1,P2,P3)

c. F –(gcd(F,Pi)/2) ≤ di/2 for each of T1,T2,T3

d. 2×F – gcd(F,Pi) ≥ di for each of T1,T2,T3

e. F – 2×gcd(F,ei) > di for each of T1,T2,T3

 A, D. c
1 point
Suppose three periodic tasks with execution times of 30 milliseconds, 40 milliseconds, and 50 milliseconds, and periods of 200 milliseconds, 300 milliseconds, and 400 milliseconds are to be run using a basic table-driven scheduler. What is the minimum time period for which the task schedule should be stored in a schedule table?a. 900millisecconds

b. 1000 milliseconds

c. 1200 milliseconds

d. 2400milliseconds

e. 3600milliseconds

Ans – – All

1 point
Suppose a foreground-background task scheduler is being used in a certain real-time system. In this system, there are two periodic foreground tasks with periods of 100 milliseconds and 150 milli Seconds, and execution times of 20 milli Seconds, and 50 milli Seconds respectively. The background task requires execution time of 700 milli Seconds. Both the foreground and background tasks arrive with zero phasing. How long will the background task take to complete?

a. 1200 milli Seconds

b. 1250 milli Seconds

c. 1500 milli Seconds

d. 2000 milli Seconds

e. 2750 milli Seconds

Ans – B, E
1 point
Suppose a cyclic scheduler is to be used to schedule a set of periodic hard real-time tasks. Which one of the following constraints sets an upper bound on the allowable frame size?a. Frame size should be larger than the size of each task.

b. Frame size should squarely divide major cycle.

c. Between the arrival of a task and its deadline, at least one full frame must exist.

d. Frame boundaries are defined using a periodic timer

e. Tasks are allocated to different frames

Ans – B, C, D
1 point
Suppose in an embedded application being developed, a set of periodic hard real-time tasks are to be scheduled using a cyclic scheduler. Assume that in the future upgradations of the embedded system, no new real-time tasks are envisaged. The designer determines that more than one frame size satisfies all the constraints on frame size. Which frame size should be chosen?a. The largest frame size

b. The smallest frame size

c. An intermediate frame size

d. The average of the frame sizes

e. None of the frame size can be chosen as the task set becomes unschedulable

Ans – E. D

1 point
Which one of the following statements concerning a cyclic scheduler is false?

a. No task preemption within a frame is allowed

b. Frame boundaries are marked through interrupts generated from a one-shot timer.

c. A selected frame size should be larger than the execution time of each task

d. Each major cycle contains an integral number of frames

e. Some of the frame may not be assigned any task

Ans -C,D,E