Lecture 9: CPU Scheduling 3

Question 1

Real-Time

Answer 1

Processes must/ should complete by some deadline

Question 2

Hard Real-Time(Must):

Answer 2

Requires dedicated scheduler

e.g.: adjust landing gear on an aircraft

Question 3

Soft Real-Time(Should):

Answer 3

Can be integrated into Multi-level Feedback Queues
•Can be integrated into priority-based scheduler (e.g.: MFQ’s)
→ should not be demoted
→ requires strict time-slices
e.g.: deliver audio / video packets

Question 4

Real-Time Scheduling

Answer 4

1. Determine “feasible” processes (deadline –now ≥ burst)
   • Re-determine at every context switch
2. Greedy heuristic:
   Choose process with min value of [deadline –(now + burst)]