Mixed-Criticality Scheduling on Multiprocessors Using Task Grouping

Abstract

Real-time systems are increasingly running a mix of tasks with different criticality levels: for instance, unmanned aerial vehicle has multiple software functions with different safety criticality levels, but runs them on a single, shared computational platform. In addition, these systems are increasingly deployed on multiprocessor platforms because this can help to reduce their cost, space, weight, and power consumption. To assure the safety of such systems, several mixed-criticality scheduling algorithms have been developed that can provide mixed-criticality timing guarantees. However, most existing algorithms have two important limitations: they do not guarantee strong isolation among the high-criticality tasks, and they offer poor realtime performance for the low-criticality tasks. Abstract-Real-time systems are increasingly running a mix of tasks with different criticality levels: for instance, unmanned aerial vehicle has multiple software functions with different safety criticality levels, but runs them on a single, shared computational platform. In addition, these systems are increasingly deployed on multiprocessor platforms because this can help to reduce their cost, space, weight, and power consumption. To assure the safety of such systems, several mixed-criticality scheduling algorithms have been developed that can provide mixed-criticality timing guarantees. However, most existing algorithms have two important limitations: they do not guarantee strong isolation among the high-criticality tasks, and they offer poor real-time performance for the low-criticality tasks. Disciplines Computer Engineering | Computer SciencesIn this paper, we present a partitioned scheduling scheme for mixed-criticality tasks on multiprocessor platforms that addresses both issues. Our scheduling scheme consists of (i) a task-toprocessor packing algorithm that takes into account the demands of tasks with respect to their criticality levels, and (ii) a mixedcriticality uniprocessor scheduling strategy that is based on task grouping. Our strategy associates each high-criticality task with a subset of the low-criticality tasks and encapsulates them in a task group, which is scheduled with the other task groups under the Earliest Deadline First (EDF) policy. Within each task group, the low-criticality task and the high-criticality tasks are scheduled using a server-based strategy, so as to enable more of the former to meet their deadlines without affecting the latter. We present a schedulability analysis for our scheduling strategy, and we show how tasks can be grouped using Mixed Integer Nonlinear Programming. Our evaluation shows that our proposed scheme significantly outperforms existing partitioned mixed-criticality scheduling algorithms, in terms of both the fraction of schedulable task sets and its ability to schedule low-criticality tasks.

Towards compositional mixed-criticality real-time scheduling in open systems

“…Using component-mode, they identify fine-grained execution behaviors of jobs in a component. However, they still have pessimism that all components request up to their HI-criticality budgets when a single component requests its HI-criticality budget [7] or all LO-tasks in a component are dropped at component mode-switch [9]. Our task-mode identifies more fine-grained execution behaviors in the system.…”

“…For example, avionic system development is subject to ARINC standard [1] (composability) and DO-178B standard (MC characteristic). Recent MC schemes support open system design [7,9]. In this section, we will extend EDF-VD-TM considering open system.…”

“…Overcoming the limitation of system mode, compositional MC approaches [7,9] introduced a concept of component-mode, which represents runtime criticality mode for a component. Using component-mode, they identify fine-grained execution behaviors of jobs in a component.…”

“…Little attention has made to efficiently scheduling mixed-criticality components in a compositional manner in open systems, except recent studies [7,9]. Although traditional temporal isolation only consider strict isolation between components, we plan to consider a diverse levels (degrees) of temporal isolation in consideration of mixedcriticality.…”

“…However, such an assumption is very unlikely to happen in practice. Recently, a few studies considered this issue [5,7,9,11] and proposed approaches to improve resource utilization for low-criticality tasks. We plan to consider this issue for compositional mixed-criticality scheduling in open systems.…”