Realtime Operating System
- Task
- Arrival time, deadline, computation time
- Periodic vs aperiodic
- Types
- Hard - missing deadline is catastrophic
- Soft - Zero value after deadline
- Decreasing value after deadline
Scheduling
- RMS
- Rate Monotonic Scheduling
- Shorter period = higher priority
- Tasks that are not done in time can be preempted.
- Easy to implement, fixed priority, not always full utilization
- EDF
- Earliest Deadline First
- Earliest deadline = higher priority
- Fairly simple, full utilization
- LLF
- Least Laxity First
- Don’t start if there is not enough time!
- Shorter period = higher priority