Date of Award
12-1-2010
Degree Name
Master of Science
Department
Electrical and Computer Engineering
First Advisor
Ramaprasad, Harini
Abstract
Embedded/real-time systems are becoming ubiquitous in today's world and their pervasive nature is increasing with the advent of cyber-physical systems. Providing temporal guarantees is paramount in such systems. Most of the normal operation in real-time systems is modelled using periodic tasks. Event-driven behaviour is modelled using aperiodic jobs. To ensure an acceptable Quality of Service for aperiodic jobs without jeopardizing safety of periodic tasks, aperiodic servers were introduced [2], [3]. Aperiodic servers are used to reserve a quota for the execution of aperiodic jobs. However, they do not take into account, cache-related delays that the execution of aperiodic jobs could impose on periodic tasks, thereby making their use in systems with caches unsafe. In this thesis, we introduce Cache Related Delay Servers to solve this problem. Statically, every periodic task's worst-case execution time includes a pre-determined delay quota for delay caused by aperiodic jobs. During system operation, the aperiodic server is allowed to execute only if periodic jobs that may be affected by it have sufficient delay quota to accommodate its execution. Otherwise, the priority of the aperiodic server is temporarily decreased to the level of the lowest-priority periodic job with insufficient quota, thereby ensuring safe execution of periodic tasks.
Access
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