Implementing Sporadic Servers in Ada
Abstract
The purpose of this paper is to present the data structures and algorithms for implementing sporadic servers in real-time systems programmed in Ada. The sporadic server algorithm is an extension of the rate monotonic scheduling algorithm (6). Sporadic servers are tasks created to provide limited and usually high-priority service for other tasks, especially aperiodic tasks. Sporadic servers can be used to guarantee deadlines for hard-deadline aperiodic tasks and provide substantial improvements in average response times for soft- deadline aperiodic tasks over polling techniques. Sporadic servers also provide a mechanism for implementing the Period Transformation technique that can guarantee that a critical set of periodic tasks will always meet their deadlines during a transient overload. Sporadic servers can also aid fault detection and containment in a real-time system by limiting the maximum execution time consumed by a task and detecting attempts to exceed a specified limit. This paper discusses two types of implementations for the sporadic server algorithm: (1) a partial implementation using an Ada task that requires no modifications to the Ada runtime system and (2) a full implementation and options for reducing this overhead are discussed. (Author) (kr)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1990
- Accession Number
- ADA226723
Entities
People
- Brinkley Sprunt
- Lui R. Sha
Organizations
- Carnegie Mellon University