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Hierarchical Real-Time Scheduling and Synchronization
Publication Type:
Licentiate Thesis
Abstract
The Hierarchical Scheduling Framework (HSF) has been introduced to enable
compositional schedulability analysis and execution of embedded software
systems with real-time constraints. In this thesis, we consider a system
consisting of a number of semi-independent components called subsystems,
and these subsystems are allowed to share logical resources. The HSF provides
CPU-time to the subsystems and it guarantees that the individual subsystems
respect their allocated CPU budgets. However, if subsystems are allowed to
share logical resources, extra complexity with respect to analysis and run-time
mechanisms is introduced.
In this thesis we address three issues related to hierarchical scheduling of
semi-independent subsystems. In the first part, we investigate the feasibility of
implementing the hierarchical scheduling framework in a commercial operating
system, and we present the detailed figures of various key properties with
respect to the overhead of the implementation.
In the second part, we studied the problem of supporting shared resources
in a hierarchical scheduling framework and we propose two different solutions
to support resource sharing. The first proposed solution is called SIRAP, a
synchronization protocol for resource sharing in hierarchically scheduled open
real-time systems, and the second solution is an enhanced overrun mechanism.
In the third part, we present a resource efficient approach to minimize system
load (i.e., the collective CPU requirements to guarantee the schedulability
of hierarchically scheduled subsystems). Our work is motivated from a tradeoff
between reducing resource locking times and reducing system load. We
formulate an optimization problem that determines the resource locking times
of each individual subsystem with the goal of minimizing the system load subject
to system schedulability. We present linear complexity algorithms to find
an optimal solution to the problem, and we prove their correctness.
Bibtex
@misc{Behnam1330,
author = {Moris Behnam},
title = {Hierarchical Real-Time Scheduling and Synchronization},
number = {94},
month = {October},
year = {2008},
url = {http://www.es.mdu.se/publications/1330-}
}