CSE 520: Real-Time Systems:Real-Time Scheduling (Single Core)

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Benefit of Scheduling Analysis

reduces development time by 50%
Consequences of a a deadline miss for a hard deadline

System fails if missed.
Consequences of a a deadline miss for a soft deadline

User may notice but system does not fail.
Goal of a hard deadline

guarantee no deadline miss.
Goal of a soft deadline

meet most deadlines, most of the time
General purpose system scheduling
- Fairness to all tasks; ergo no starvation
- Optimize throughput
- Optimize average performance
Embedded systems scheduling
- Meet ALL deadlines.
- Fairness or throughput in NOT important
- Hard Real-Time: worry about worst case performance.
Task
- Map to a process or thread
- May be released several times
Job

An instance of a task.
Periodic task
- Ideal: inter-arrival time = period
- General: inter-arrival time >= period.
Aperiodic task

Inter-arrival time does not have a lower bound.
Ti (math)

Task.
Pi (math)

period OF a task Ti.
Ci (math)

Worst-case execution time OF a task Ti.
Jik (math)

Job k OF task Ti.
Release time (math)

Time when a job is ready.
Response time Ri (math)

is equal to the finish time - release time
Absolute deadline (math).

Is equal to release time + Di (relative deadline)
A job Jik misses its deadline if
- Response time Ri > Di (relative deadline)
- Finish time > absolute deadline.
A task set is schedulable

if ALL jobs meet their deadlines.
Optimal scheduling algorithm

A task set is unschedulable under the optimal algorithm, and therefore unschedulable under any other algorithms.
Overhead (math)

Time required for scheduling.

Author

geschw66

324841

Card Set

CSE 520: Real-Time Systems:Real-Time Scheduling (Single Core)

Description

Cards cover Dr. Lu's lecture on Real-Time Scheduling from CSE 520s Real-Time Systems course Fall Semester of 2016

Updated

2016-10-23T03:36:11Z

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