Real-Time Computing: Difference between revisions
| (18 intermediate revisions by the same user not shown) | |||
| Line 2: | Line 2: | ||
* https://en.wikipedia.org/wiki/Real-time_computing | * https://en.wikipedia.org/wiki/Real-time_computing | ||
* Real-Time Computing: A New Discipline of Computer Science and Engineering https://kabru.eecs.umich.edu/papers/publications/1994/ramanathan-shin-ieee-proceedings.pdf | |||
=Internal= | =Internal= | ||
| Line 9: | Line 10: | ||
=Overview= | =Overview= | ||
A real-time system is subject to a "real-time constraint" - a guaranteed response within a specified time constraint between event to system response | A real-time system is subject to a "[[#Real-time_Constraint|real-time constraint]]" - a guaranteed response within a specified time constraint between event to system response. Real-time systems control an environment by receiving data, processing it, and returning the results sufficiently quickly to affect the environment at that time. | ||
Formally, a system is said of be real-time if the correctness of an operation depends not only upon its logical correctness, but also upon the time in which the operation is performed. Real-time systems are classified by the consequences of missing a deadline: | |||
* <span id='Hard'></span>'''Hard''' Real-time System - missing a [[#Deadline|deadline]] is a total system failure. | |||
* <span id='Firm'></span>'''Firm''' Real-time System - infrequent [[#Deadline|deadline]] misses are tolerable, but may degrade the system's quality of service. The usefulness of a result is zero after its [[#Deadline|deadline]]. | |||
* <span id='Soft'></span>'''Soft''' Real-time System - the usefulness of a result degrades after its deadline, degrading the system's quality of service. | |||
=Real-time Operating System= | =Real-time Operating System= | ||
| Line 15: | Line 21: | ||
{{External|https://en.wikipedia.org/wiki/Real-time_operating_system}} | {{External|https://en.wikipedia.org/wiki/Real-time_operating_system}} | ||
An operating system intended to serve real-time applications that process data as it comes, without [[#Buffer_Delay|buffer delays]]. | An operating system intended to serve real-time applications that process data as it comes, without [[#Buffer_Delay|buffer delays]]. The system attempts to insure [[#Real-time_Constraint|the guaranteed response time]], possibly at the expense of the throughput. | ||
=<span id='Deadline'></span>Real-time Constraint= | |||
A ''real-time constraint'' is a guaranteed response within a specified time constraint between event to system response. Real-time constraints are also referred to as "deadlines". Deadlines must always be met, regardless of system load. For [[#Hard|hard]] and [[#Firm|firm]] real-time systems, the usefulness of a result is zero after its deadline. | |||
= | =Near real-time= | ||
=Buffer Delay= | =Buffer Delay= | ||
=Jitter= | |||
Latest revision as of 00:52, 19 April 2018
External
- https://en.wikipedia.org/wiki/Real-time_computing
- Real-Time Computing: A New Discipline of Computer Science and Engineering https://kabru.eecs.umich.edu/papers/publications/1994/ramanathan-shin-ieee-proceedings.pdf
Internal
Overview
A real-time system is subject to a "real-time constraint" - a guaranteed response within a specified time constraint between event to system response. Real-time systems control an environment by receiving data, processing it, and returning the results sufficiently quickly to affect the environment at that time.
Formally, a system is said of be real-time if the correctness of an operation depends not only upon its logical correctness, but also upon the time in which the operation is performed. Real-time systems are classified by the consequences of missing a deadline:
- Hard Real-time System - missing a deadline is a total system failure.
- Firm Real-time System - infrequent deadline misses are tolerable, but may degrade the system's quality of service. The usefulness of a result is zero after its deadline.
- Soft Real-time System - the usefulness of a result degrades after its deadline, degrading the system's quality of service.
Real-time Operating System
An operating system intended to serve real-time applications that process data as it comes, without buffer delays. The system attempts to insure the guaranteed response time, possibly at the expense of the throughput.
Real-time Constraint
A real-time constraint is a guaranteed response within a specified time constraint between event to system response. Real-time constraints are also referred to as "deadlines". Deadlines must always be met, regardless of system load. For hard and firm real-time systems, the usefulness of a result is zero after its deadline.