Daniel L. Kiskis

A distributed real-time operating system

Two versions of the HARTS operating system, which is based on Software Components Groups pSOS uniprocessor kernel, are presented. In one version, pSOS services are enhanced to provide interprocessor communication and a distributed naming service. In the second version, real-time fault-tolerant communication, including reliable broadcasting, clock synchronization, and group communication are added to the HARTS operating system. Three tools to evaluate the performance and fault tolerance dependability of HARTS hardware and software-a synthetic-workload generator, a monitor, and a fault injector-are described. The generator produces a synthetic workload, the monitor collects the performance data, and the fault injector simulates faulty behavior for further study. Together these tools create a facility that lets the user perform a wide range of experiments. The tools are independent, so they are equally effective separately or together, depending on the requirements.<<ETX>>

A Digital Library for the Dissemination and Replication of Quantitative Social Science Research: The Virtual Data Center

The Virtual Data Center software is an open-source, digital library system for quantitative data. The authors discuss what the software does, how it provides an infrastructure for the management and dissemination of distributed collections of quantitative data, and the replication of results derived from these data.

HARTOS: a distributed real-time operating system

This paper outlines the design objectives and research goals for HARTOS, a distributed real-time operating system being developed at The University of Michigan. This effort is part of a larger research project to design and implement an experimental distributed real-time system called the Hexagonal Architecture for Real-Time Systems (HARTS). An important feature of HARTS is the use of an intelligent network processor to handle many of the functions relating to communications. The paper focuses on the communications aspects of the operating system and the control software kernel of the network processor. The preliminary version of the kernel provides good support for inter-process communication and distributed control. Its performance has been measured and analyzed and found to be comparable to that of other message passing systems like the V system.

SWSL: a synthetic workload specification language for real-time systems

We discuss the issues that must be addressed in the specification and generation of synthetic workloads for distributed real-time systems. We describe a synthetic workload specification language (SWSL) that defines a workload in a form that can be compiled by a synthetic workload generator (SWG) to produce an executable synthetic workload. The synthetic workload is then downloaded to the target machine and executed while performance and dependability measurements are made. SWSL defines the workload at the task level using a data flow graph, and at the operation level using control constructs and synthetic operations taken from a library. It is intended to be easy to use, flexible, and capable of creating synthetic workloads that are representative of real-time workloads. It provides a compact, parameterized notation. It supports automatic replication of objects to facilitate the specification of large workloads for distributed real-time systems. It also provides extensive support for the experimentation process. >

Measurement of OS services and its application to performance modeling and analysis of integrated embedded software

Performance analyses for embedded software construction with existing components require knowledge of performance characteristics of both application software and operating system (OS) services, especially those services that are critical for real-time applications. Since end users normally do not control the structure and implementation of OS services, but have to use them to meet the system-level performance constraints, it is essential and critical to characterize the performance of OS services with measurements. As such measurements are taken for performance analysis, not for comparison, the measurement methods should be different from those traditionally, used for comparison. In this paper we present an end-to-end method for measuring the performance of timing and scheduling services in selected real-time OSs for the performance modeling and analysis. The proposed method takes the factors of both OS implementations and application configurations into account to obtain the measured performance close to what applications will experience at runtime. The results have shown that the performance characteristics of OS services can be measured without instrumenting the kernel source code, and hence, can be reused for the analysis of a family of applications.

A synthetic workload for a distributed real-time system

In this paper, we describe the design and implementation of a synthetic workload (SW) for a distributed real-time system. A SW is a set of parameterized synthetic or artificial programs which serve as the workload for a system under study. The parameterized nature of the programs allows the user to change their behavior to create different resource demands on the system. The SW is easy to use, flexible, and can be representative of a real-time workload. The SW consists of a driver and a set of synthetic tasks. The synthetic tasks are generated by a synthetic workload generator (SWG) from the users specification written in SWSL, a synthetic workload specification language. We describe the design goals of our SW and discuss its software structure and how it meets these goals.

Overview of the virtual data center project and software

In this paper, we present an overview of the Virtual Data Center (VDC) software, an open-source digital library system for the management and dissemination of distributed collections of quantitative data. (see ). The VDC functionality provides everything necessary to maintain and disseminate an individual collection of research studies, including facilities for the storage, archiving, cataloging, translation, and on-line analysis of a particular collection. Moreover, the system provides extensive support for distributed and federated collections including: location-independent naming of objects, distributed authentication and access control, federated metadata harvesting, remote repository caching, and distributed virtual collections of remote objects.

Embedding triple-modular redundancy into a hypercube architecture

This paper describes an embedding of Triple Modular Redundancy (TMR) into a binary hypercube. The goal is to improve fault tolerance by masking any single-point faults. Each module of an application task is triplicated and executed in parallel on three nodes of a 2-dimensional subcube (Q2) of the hypercube. Each of these nodes also executes a voter process. The remaining node is used for message passing only. All outputs from the triplicated modules are voted on, and the voting results are transmitted to the appropriate destination. Thus, all interunit messages are also triplicated. We propose an embedding of TMR into a hypercube which can be implemented in a manner transparent to the application program. Subcubes are allocated so that the address space for the TMR units is also a hypercube. Hence, the subcube allocation and intermodule communication schemes are defined to be analogous to the schemes used in the nonredundant system. The embedded system is proven to mask all single-point faults.

System Support for Management of Networked Low-Power Sensors

This paper addresses the problem of managing a wireless sensor network with mobile managers. The mobile managers should be able to create their connectivity to the nodes they manage, and advertise their interests in the management data to be collected. Also, the network nodes should self-manage their connectivity to the managers in order to forward the management data. To meet these requirements, we propose (1) an algorithm for creating and maintaining encounter-associated management connectivity and (2) both management data exchange protocols and programming abstractions for network management applications. Both our simulation-based evaluation and experimentation of the proposed algorithm and architectural elements on real sensors demonstrated their effectiveness in meeting the requirements