AADL modeling and analysis of hierarchical schedulers

Abstract

A system based on a hierarchical scheduler is a system in which the processor is shared between several collaborative schedulers. Such schedulers exist since 1960 and they are becoming more and more investigated and proposed in real-life applications. For example, the ARINC 653 international standard which defines an Ada interface for avionic real time operating systems provides such a kind of collaborative schedulers. This article focuses on the modeling and the performance analysis of hierarchical schedulers. We investigate the modeling of hierarchical schedulers with AADL. Hierarchical scheduler timing and synchronization relationships are expressed with a domain specific language based on timed automata: the Cheddar language. With the meta CASE tool Platypus, we generate Ada packages implementing the Cheddar language. These Ada packages are part of Cheddar, a real time scheduling simulator. With these Ada packages, Cheddar is able to perform analysis by scheduling simulation of AADL systems composed of hierarchical schedulers. An AADL model of the ARINC 653 hierarchical scheduling is described as an illustration.