Generalized Elastic Scheduling for Real-Time Tasks

Abstract

Abstract-The elastic task model is a powerful model for adapting periodic real-time systems in the presence of uncertainty. This paper generalizes the existing elastic scheduling approach in several directions. It reveals that the original task compression algorithm in fact solves a quadratic programming problem that seeks to minimize the sum of the squared deviation of a task's utilization from initial desired utilization. This finding indicates that the task compression algorithm may be applied to efficiently solve other similar types of problems that often arise in real-time applications. In particular, an iterative approach is proposed to solve the task compression problem for real-time tasks with deadlines less than respective periods. Furthermore, the framework is generalized to adjust task deadlines instead of task periods.

Local Adjustment and Global Adaptation of Control Periods for QoC Management of Control Systems

“…Elastic scheduling was proposed in [14] to adjust the periods for flexible workload management through the compressing algorithm. It was further developed in a general optimization framework [15]. Cervin [16] developed a method incorporating with the EDF to re-scale the periods in overload conditions.…”

WiP Abstract: Supporting Coordinated Negotiation in CPS Design

“…In cyber-physical system (CPS) design, it is critical to systematically exploit the interplay between the control strategies and the implementation alternatives, such as the intelligent coordination presented in [1], [3], [5]. Negotiation between the two sides could be facilitated through appropriately choosing task models and dynamically managing task execution.…”

“…The elastic task model [2], [3] may be able to model the above system, because task periods can be any value within a given range. However, the choices of the actual period values are made based on satisfying the timing requirement instead of in response to the physical system's requirement.…”

The Continuous Stream Model of Computation for Real-Time Control

“…More closely related to our idea is the work of Marti et al [5], who propose to re-modulate the task periods in response to an overload condition. In the same direction goes the work of Lemmon et al [7] and of Fontanelli et al [10], [11], who develop a Markov Chain model to describe the possible activations of the control task that can be skipped without compromising stability. This Markovian model can be used to construct a jump linear system [19] describing the closed loop dynamics, which in its turn can be used to show stability or other control theoretical properties.…”