End-to-End Scheduling Strategies for Aperiodic Tasks in Middleware

Many mission-critical distributed real-time applicationsmust handle aperiodic tasks with hard end-to-end dead-lines. Existing middleware such as RT-CORBA lacksschedulability analysis and run-time scheduling mecha-nisms that can provide real-time guarantees to aperiodictasks. This paper makes the following contributions to thestate of the art for end-to-end aperiodic scheduling in mid-dleware. First, we compare two approaches to aperiodicscheduling, the deferrable server and the aperiodic utiliza-tion bound, using representative workloads. Numerical re-sults show that the deferrable server analysis is less pes-simistic than the aperiodic utilization bounds when appliedoffline. Second, we propose a practical approach to tuningdeferrable servers for end-to-end tasks. Third, we describedeferrable server mechanisms we have developed for TAO’sfederated event channel. Finally, we present empirical re-sults from a Linux testbed that demonstrate the efficiency ofthose deferrable server mechanisms

Middleware Support for Aperiodic Tasks in Distributed Real-Time Systems

Many mission-critical distributed real-time applications must handle aperiodic tasks with end-to-end deadlines. However, existing middleware (e.g., RT-CORBA) lacks schedulability analysis and run-time enforcement mecha-nisms needed to give online real-time guarantees for ape-riodic tasks. The primary contribution of this work is the design, implementation, and performance evaluation of the first realization of deferrable server and admission control mechanisms for aperiodic tasks in middleware. Empirical results on a KURT-Linux testbed demonstrate the efficiency and effectiveness of our deferrable server and admission control mechanisms in TAO’s federated event service.

A Feasible Region for Meeting Aperiodic End-to-end Deadlines in Resource Pipelines

This paper generalizes the notion of utilization bounds for schedulability of aperiodic tasks to the case of distributed resource systems. In the basic model, aperiodically arriving tasks are processed by multiple stages of a resource pipeline within end-to-end deadlines. The authors consider a multi-dimensional space in which each dimension represents the instantaneous utilization of a single stage. A feasible region is derived in this space such that all tasks meet their deadlines as long as pipeline resource consumption remains within the feasible region. The feasible region is a multi-dimensional extension of the single-resource utilization bound giving rise to a bounding surface in the utilization space rather than a scalar bound. Extensions of the analysis are provided to non-independent tasks and arbitrary task graphs. We evaluate the performance of admission control using simulation, as well as demonstrate the applicability of these results to task schedulability analysis in the total ship computing environment envisioned by the US navy

Implementation Experience £ with OMG’s SCIOP Mapping

Abstract. Longevity of distributed computing middleware standards, such as CORBA, depend on their ability to support a range of applications by providing low overhead access in a uniform manner to a large variety of platforms and network capabilities. OMG’s recent adaptation of Stream Control Transmission Protocol (SCTP) mapping is another instance of this trend. Applications can obtain all the benefits of this emerging protocol via a standard compliant, distributed object model. This paper reports on integration of SCTP with Adaptive Communications Framework (ACE) [2] and The Ace ORB (TAO). [3] By exploiting network path multiplexing capability of SCTP we demonstrate that CORBA applications can bound the maximum latencies they suffer under stressful network failures to under 50 msec.

A Multi-layered Resource Management Framework for Dynamic Resource Management

Enterprise distributed real-time and embedded (DRE) systems can benefit from dynamic management of computing and networking resources to optimize and reconfigure system resources at runtime in response to changing mission needs and/or other situations, such as failures or system overload. This paper provides two contributions to the study of dynamic resource management (DRM) for enterprise DRE systems. First, we describe a standards-based multi-layered resource management (MLRM) architecture that provides DRM capabilities to enterprise DRE systems. Second, we show the results of experiments evaluating our MLRM architecture in the context of a representative enterprise DRE system for shipboard computing. ware Keywords:Dynamic Resource Management, Enterprise DRE Systems, QoS-enabled Component Middle-