2,303 research outputs found
Scheduling Issues in Real-Time Systems
The most important objective of real-time systems is to fulfill time-critical
missions in satisfying their application requirements and timing constraints.
Software utilities can analyze real-time tasks and extract their characteristics
and requirements for assisting the systems to guarantee schedulability. Real-
time scheduling is the core of the real-time system design. It should allow
real-time systems to exhibit predictable timing correctness regardless of
possible uncertainty in run-time environments. In this dissertation, we study
the problem of scheduling real-time tasks with resource and fault-tolerance
requirements. For tasks with resource requirements, two types of platforms are
examined: multiprocessor hard real-time systems and real-time database systems;
for task with fault-tolerance requirements, we focus on hard real-time systems.
We investigate preemptive priority-based scheduling for tasks with resource
requirements in context of hard real-time systems. Rate-monotonic and earliest
deadline first priority assignment strategies can meet deadlines if the
schedulability conditions are satisfied. We propose resource control protocols,
for these scheduling strategies, based on the concepts of priority inheritance
and priority ceiling and describe schedulability conditions for meeting
deadlines.
Real-time database systems have different objectives for transaction scheduling.
Minimizing miss ratio usually is the major concern. We study the significance of
the knowledge of execution time in system performance and propose a class of
optimistic concurrency control protocols using the knowledge of execution time.
Our simulation results indicate that the knowledge of execution time
substantially improve system performance.
Fault-tolerance is an ability to maintain system in a safe and stable state
such that the real-time application functions correctly and its timing
constraints are satisfied even in the presence of faults. We develop a
scheduling algorithm which attempts to build as many fault-tolerant tasks as
possible into a schedule. We approximate system reliability by Markov chain
models and illustrate the applicability of the proposed reliability models.
We compare the proposed fault-tolerance scheduling approach with the basic
fault-tolerance scheduling schemes and the simulation results show that our
method provides better reliability than the basic scheduling schemes.
(Also cross-referenced as UMIACS-TR-95-73
Problems related to the integration of fault tolerant aircraft electronic systems
Problems related to the design of the hardware for an integrated aircraft electronic system are considered. Taxonomies of concurrent systems are reviewed and a new taxonomy is proposed. An informal methodology intended to identify feasible regions of the taxonomic design space is described. Specific tools are recommended for use in the methodology. Based on the methodology, a preliminary strawman integrated fault tolerant aircraft electronic system is proposed. Next, problems related to the programming and control of inegrated aircraft electronic systems are discussed. Issues of system resource management, including the scheduling and allocation of real time periodic tasks in a multiprocessor environment, are treated in detail. The role of software design in integrated fault tolerant aircraft electronic systems is discussed. Conclusions and recommendations for further work are included
Fault-free performance validation of fault-tolerant multiprocessors
A validation methodology for testing the performance of fault-tolerant computer systems was developed and applied to the Fault-Tolerant Multiprocessor (FTMP) at NASA-Langley's AIRLAB facility. This methodology was claimed to be general enough to apply to any ultrareliable computer system. The goal of this research was to extend the validation methodology and to demonstrate the robustness of the validation methodology by its more extensive application to NASA's Fault-Tolerant Multiprocessor System (FTMP) and to the Software Implemented Fault-Tolerance (SIFT) Computer System. Furthermore, the performance of these two multiprocessors was compared by conducting similar experiments. An analysis of the results shows high level language instruction execution times for both SIFT and FTMP were consistent and predictable, with SIFT having greater throughput. At the operating system level, FTMP consumes 60% of the throughput for its real-time dispatcher and 5% on fault-handling tasks. In contrast, SIFT consumes 16% of its throughput for the dispatcher, but consumes 66% in fault-handling software overhead
Designing and Valuating System on Dependability Analysis of Cluster-Based Multiprocessor System
Analysis of dependability is a significant stage in structuring and examining the safety of protection systems and computer systems. The introduction of virtual machines and multiprocessors leads to increasing the faults of the system, particularly for the failures that are software- induced, affecting the overall dependability. Also, it is different for the successful operation of the safety system at any dynamic stage, since there is a tremendous distinction in the rate of failure among the failures that are induced by the software and the hardware. Thus this paper presents a review or different dependability analysis techniques employed in multiprocessor system
Performance and evaluation of real-time multicomputer control systems
Three experiments on fault tolerant multiprocessors (FTMP) were begun. They are: (1) measurement of fault latency in FTMP; (2) validation and analysis of FTMP synchronization protocols; and investigation of error propagation in FTMP
Framework for Simulation of Heterogeneous MpSoC for Design Space Exploration
Due to the ever-growing requirements in high performance data computation, multiprocessor systems have been proposed to solve the bottlenecks in uniprocessor systems. Developing efficient multiprocessor systems requires effective exploration of design choices like application scheduling, mapping, and architecture design. Also, fault tolerance in multiprocessors needs to be addressed. With the advent of nanometer-process technology for chip manufacturing, realization of multiprocessors on SoC (MpSoC) is an active field of research. Developing efficient low power, fault-tolerant task scheduling, and mapping techniques for MpSoCs require optimized algorithms that consider the various scenarios inherent in multiprocessor environments. Therefore there exists a need to develop a simulation framework to explore and evaluate new algorithms on multiprocessor systems. This work proposes a modular framework for the exploration and evaluation of various design algorithms for MpSoC system. This work also proposes new multiprocessor task scheduling and mapping algorithms for MpSoCs. These algorithms are evaluated using the developed simulation framework. The paper also proposes a dynamic fault-tolerant (FT) scheduling and mapping algorithm for robust application processing. The proposed algorithms consider optimizing the power as one of the design constraints. The framework for a heterogeneous multiprocessor simulation was developed using SystemC/C++ language. Various design variations were implemented and evaluated using standard task graphs. Performance evaluation metrics are evaluated and discussed for various design scenarios
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