FSF: A Real-Time Scheduling Architecture Framework

Scheduling theory generally assumes that real-time systems are mostly composed of activities with hard real-time requirements. Many systems are built today by composing different applications or components in the same system, leading to a mixture of many different kinds of requirements with small parts of the system having hard real-time requirements and other larger parts with requirements for more flexible scheduling and for quality of service. Hard real-time scheduling techniques are extremely pessimistic for the latter part of the application, and consequently it is necessary to use techniques that let the system resources be fully utilized to achieve the highest possible quality. This paper presents a framework for a scheduling architecture that provides the ability to compose several applications or components into the system, and to flexibly schedule the available resources while guaranteeing hard real-time requirements. The framework (called FSF) is independent of the underlying implementation, and can run on different underlying scheduling strategies. It is based on establishing service contracts that represent the complex and flexible requirements of the applications, and which are managed by the underlying system to provide the required level of service.