Nowadays, Field-Programmable Gate Arrays (FP-GAs) are increasingly used in critical applications. In these scenarios fault tolerance techniques are needed to increase system dependability and lifetime. This paper proposes a novel methodology to achieve autonomous fault tolerance in FPGA-based systems affected by permanent faults. A design flow is defined to help designers to build a system with increased lifetime and availability. The methodology exploits Dynamic Partial Reconfiguration (DPR) to relocate at run-time faulty modules implemented onto the FPGA. A partitioning method is also presented to provide a solution which maximizes the number of permanent faults the system can tolerate. Experimental results highlight the negligible performance degradation introduced by applying the proposed methodology, and the improvements with respect to state-of-the-art solutions.

System reliability estimation during early design phases facilitates informed decisions for the integration of effective protection mechanisms against different classes of hardware faults. When not all system abstraction layers (technology, circuit, microarchitecture, software) are factored in such an estimation model, the delivered reliability reports must be excessively pessimistic and thus lead to unacceptably expensive, over-designed systems. We propose a scalable, cross-layer methodology and supporting suite of tools for accurate but fast estimations of computing systems reliability. The backbone of the methodology is a component-based Bayesian model, which effectively calculates system reliability based on the masking probabilities of individual hardware and software components considering their complex interactions. Our detailed experimental evaluation for different technologies, microarchitectures, and benchmarks demonstrates that the proposed model delivers very accurate reliability estimations (FIT rates) compared to statistically significant but slow fault injection campaigns at the microarchitecture level.Peer ReviewedPostprint (author's final draft

International audienceAdvanced computing systems realized in forthcoming technologies hold the promise of a significant increase of computational capabilities. However, the same path that is leading technologies toward these remarkable achievements is also making electronic devices increasingly unreliable. Developing new methods to evaluate the reliability of these systems in an early design stage has the potential to save costs, produce optimized designs and have a positive impact on the product time-to-market

Cross-layer reliability is becoming the preferred solution when reliability is a concern in the design of a microprocessor-based system. Nevertheless, deciding how to distribute the error management across the different layers of the system is a very complex task that requires the support of dedicated frameworks for cross-layer reliability analysis. This paper proposes SyRA, a system-level cross-layer early reliability analysis framework for radiation induced soft errors in memory arrays of microprocessor-based systems. The framework exploits a multi-level hybrid Bayesian model to describe the target system and takes advantage of Bayesian inference to estimate different reliability metrics. SyRA implements several mechanisms and features to deal with the complexity of realistic models and implements a complete toolchain that scales efficiently with the complexity of the system. The simulation time is significantly lower than micro-architecture level or RTL fault-injection experiments with an accuracy high enough to take effective design decisions. To demonstrate the capability of SyRA, we analyzed the reliability of a set of microprocessor-based systems characterized by different microprocessor architectures (i.e., Intel x86, ARM Cortex-A15, ARM Cortex-A9) running both the Linux operating system or bare metal in the presence of single bit upsets caused by radiation induced soft errors. Each system under analysis executes different software workloads both from benchmark suites and from real applications.

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Analyzing the impact of software execution on the reliability of a complex digital system is an increasing challenging task. Current approaches mainly rely on time consuming fault injections experiments that prevent their usage in the early stage of the design process, when fast estimations are required in order to take design decisions. To cope with these limitations, this paper proposes a statistical reliability analysis model based on Bayesian Networks. The proposed approach is able to estimate system reliability considering both the hardware and the software layer of a system, in presence of hardware transient and permanent faults. In fact, when digital system reliability is under analysis, hardware resources of the processor and instructions of program traces are employed to build a Bayesian Network. Finally, the probability of input errors to alter both the correct behavior of the system and the output of the program is computed. According to experimental results presented in this paper, it can be stated that Bayesian Network model is able to provide accurate reliability estimations in a very short period of time. As a consequence it can be a valid alternative to fault injection, especially in the early stage of the design.

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