Glossary · Automation software engineering and architecture
Task scheduler
Also known as: Scheduler
German: Task-Scheduler
In operating systems and runtime environments, a task scheduler is the component that decides which task or thread runs on a processor at a given time, according to a scheduling policy such as fixed priorities, time slices or deadlines.
- Software engineering
In one sentence
A task scheduler decides which task runs on a processor at any time, following a policy such as fixed priorities or deadlines.
Example
The PLC runtime's scheduler starts the 10 ms task every 10 ms, lets it preempt the free-running task and reports a cycle overrun if it does not finish in time.
How it applies
- Engineering: The scheduling policy determines response times and Jitter. PLC runtimes offer cyclic, event-triggered and free-running tasks with priorities; the configuration of these tasks is a design decision.
- Verification: Cycle time monitoring and task trace tools show whether tasks meet their periods. Overruns are usually diagnosed and can stop the controller.
- Documentation: Controller manuals should explain task types, priorities, watchdog times and overrun behavior clearly, because task configuration errors are common in commissioning.
Task scheduler vs. job scheduling
A task scheduler allocates processor time within a computer in microseconds to milliseconds. Job scheduling in production or IT plans work orders or batch jobs over minutes to days.