L4

Question 1

What is task scheduling?

Answer 1

The decision of when, in which order and where different jobs must execute

Question 2

Why and how scheduling?

Answer 2

We must have some task execution ordering mechanism

Question 3

Where do the timing constraints come from?

Answer 3

From requirements (e.g. open the door within x ms)

Question 4

How do we guarantee timing constraints?

Answer 4

Through schedulability (and analysis)!

• based on appropriate task parameters (e.gg periods, deadlines, priorities, etc)

Question 5

CPU Utilization

Answer 5

U = C1/T1 + C2/T2 + ….<= 1

Question 6

Scheduling approaches

Answer 6

Offline scheduling
- performed before system deployment
- generates a “timetable” that efindes the run-time execution
- also called static or pre-run-time scheduling

Online scheduling
- scheduling decision performed during the system execution
- based on task priorities
- also called dynamic or run-time scheduling

Question 7

Event-triggered and Time-triggered real-time-systems

Answer 7

Event-triggerd
- online scheduling

Time-triggered
- offline scheduling

Question 8

RM, DM, EDF, PIP

Answer 8

RM: Rate Monotonic
DM: Deadline Monotonic
EDF: Earliest Deadline First
PIP: Priority Inheritance Protocol

Question 9

Rate Monotonic Schedulability condition:

Answer 9

U <= n(2⁽¹/n⁾-1)