Open Access Dissertation
Date of Award
We introduce a new design metric called system-resiliency which characterizes the maximum unpredictable
external stresses that any hard-real-time performance mode can withstand. Our proposed systemresiliency
framework addresses resiliency determination for real-time systems with physical and hardware
limitations. Furthermore, our framework advises the system designer about the feasible trade-offs between
external system resources for the system operating modes on a real-time system that operates in a
multi-parametric resiliency environment.
Modern multi-modal real-time systems degrade the system’s operational modes as a response to unpredictable
external stimuli. During these mode transitions, real-time systems should demonstrate a reliable
and graceful degradation of service. Many control-theoretic-based system design approaches exist. Although
they permit real-time systems to operate under various physical constraints, none of them allows
the system designer to predict the system-resiliency over multi-constrained operating environment. Our
framework fills this gap; the proposed framework consists of two components: the design-phase and runtime
control. With the design-phase analysis, the designer predicts the behavior of the real-time system for
variable external conditions. Also, the runtime controller navigates the system to the best desired target
using advanced control-theoretic techniques. Further, our framework addresses the system resiliency of
both uniprocessor and multicore processor systems.
As a proof of concept, we first introduce a design metric called thermal-resiliency, which characterizes
the maximum external thermal stress that any hard-real-time performance mode can withstand. We verify
the thermal-resiliency for the external thermal stresses on a uniprocessor system through a physical testbed.
We show how to solve some of the issues and challenges of designing predictable real-time systems that
guarantee hard deadlines even under transitions between modes in an unpredictable thermal environment
where environmental temperature may dynamically change using our new metric.
We extend the derivation of thermal-resiliency to multicore systems and determine the limitations of
external thermal stress that any hard-real-time performance mode can withstand. Our control-theoretic
framework allows the system designer to allocate asymmetric processing resources upon a multicore proiii
cessor and still maintain thermal constraints.
In addition, we develop real-time-scheduling sub-components that are necessary to fully implement our
framework; toward this goal, we investigate the potential utility of parallelization for meeting real-time
constraints and minimizing energy. Under malleable gang scheduling of implicit-deadline sporadic tasks
upon multiprocessors, we show the non-necessity of dynamic voltage/frequency regarding optimality of
our scheduling problem. We adapt the canonical schedule for DVFS multiprocessor platforms and propose
a polynomial-time optimal processor/frequency-selection algorithm.
Finally, we verify the correctness of our framework through multiple measurable physical and hardware
constraints and complete our work on developing a generalized framework.
Hettiarachchi, Pradeep Mahendra, "A Control-Theoretic Design And Analysis Framework For Resilient Hard Real-Time Systems" (2015). Wayne State University Dissertations. 1339.