Difference between Sporadic and Aperiodic Real-time Tasks
Last Updated :
14 May, 2020
There are two types of tasks in real-time systems: Periodic tasks, and Dynamic tasks.
Further Dynamic Tasks are classified as:
1. Sporadic Real-time Tasks :
The real-time tasks that reoccur at any random instant and have hard deadline are known as sporadic real-time tasks. Sporadic real-time tasks have some similarity to aperiodic real-time tasks but these tasks are different from aperiodic real-time tasks. Basically all the high critical tasks are sporadic tasks.
For example, fire handling task in industry or emergency message arrival in system are sporadic real-time tasks.
2. Aperiodic Real-time Tasks :
The dynamic tasks that reoccur at any random time and have soft deadline are known as aperiodic real-time tasks. Between two aperiodic real-time tasks the time interval may be even zero. Aperiodic real-time tasks generally include soft real-time tasks.
For example, typing on keyboard or mouse movements are aperiodic real-time tasks.
Difference between Sporadic and Aperiodic Real-time Tasks:
SPORADIC TASK |
APERIODIC TASK |
It has hard deadline. |
It has soft deadline or no deadline. |
It is highly critical task. |
It is low or moderate critical task. |
The minimum separation between two consecutive instances can not be zero. |
the minimum separation between two consecutive instances can be zero. |
It includes hard real-time tasks. |
It includes soft real-time tasks. |
Deadline of all instances of sporadic task can be meet easily. |
To meet deadline of all instances of aperiodic task is difficult. |
It goes through acceptance test. |
No testing is performed on aperiodic task. |
It is executed only when sufficient slack time is available. |
Its execution does not depend on available slack time. |
It gets rejected by scheduler when there is less slack time. |
It never get rejected by scheduler. |
It includes commands given by the system. |
It includes interactive commands given by the user. |
Example: Security alert program in system. |
Example: Logging task in system. |
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