System reliability has become a first-class design constraint. As the use of Graphics Processing Units (GPU) continues to increase in compute applications, including High Performance Computing (HPC) and safety-critical applications, so do the number of transient faults in GPUs. However, our understanding of the potential impact of transient fault propagation in GPU applications remains limited. This study shows that the resilience characteristics of GPU programs change significantly during program execution and these characteristics show repetitive, time-varying behavior. Interestingly, these repetitive, time-varying, resilience characteristics of GPU programs do not align or correlate well with the performance phases of GPU programs. Furthermore, this work discovers and validates that temporal changes in the vulnerability behavior during a kernel execution tends to coincide with changes in basic block execution paths. Finally, we demonstrate how these observations can be exploited to accelerate the fault injection campaigns for reliability assessment of GPU programs by an order of magnitude and open opportunities for designing other effective resilience mitigation strategies.

The vulnerability of GPUs to soft errors has become a first-class design concern as they are increasingly being used in accuracy-sensitive and safety-critical domains. Existing solutions used to enhance the reliability of GPUs come with significant overhead in terms of area, power, and/or performance. In this article, we propose ArmorAll, a light-weight, adaptive, selective, and portable software solution to protect GPUs against soft errors. ArmorAll consists of a set of purely compiler-based redundancy schemes designed to optimize instruction duplication on GPUs, thereby enabling much more reliable execution. The choice of the scheme determines the subset of instructions that must be duplicated in an application, allowing adaptable fault coverage for different applications. ArmorAll can intelligently select a redundancy scheme that provides the best coverage to an application with an accuracy of 91.7%. The high coverage provided by ArmorAll comes at an average improvement of 64.5% in runtime when using the selected redundancy scheme as compared to the state-of-the-art.

Reliability has become a first-class design objective for GPU devices due to increasing soft-error rate. To assess the reliability of GPU programs, researchers rely on software fault-injection methods. Unfortunately, software fault-injection process is prohibitively expensive, requiring multiple days to complete a statistically sound fault-injection campaign. Therefore, to address this challenge, this paper proposes a novel fault-injection method, PCFI, that reduces the number of fault injections by exploiting the predictability in fault-injection outcome based on the program counter of the soft-error affected instruction. Evaluation on a variety of GPU programs covering a wide range of application domains shows that PCFI reduces the time to complete fault-injection campaigns by 22% on average, without sacrificing accuracy.

While transient faults continue to be a major concern for the High Performance Computing (HPC) community, we still lack a clear understanding of how these faults propagate in applications. This paper addresses two particular aspects of the vulnerabilities of HPC applications as run on Graphics Processing Units (GPUs): their dependence on input data and on thread-block size. To characterize fault propagation as a function of input parameters, we leverage an ISA-level fault injection framework and carry out an extensive fault injection campaign to characterize the vulnerability of a suite of GPU applications. Our results show that the vulnerability of most of the programs studied are insensitive to changes in input values, except in less common cases when input values were highly biased, i.e., values that exhibit a special vulnerability behavior. For example, the multiplication property of any value with a zero value (zero times any number is equal to zero) makes it a biased input for multiplication operations. Our study also examines the effects of changing the GPU thread-block size and its impact on vulnerability. We found that, similar to performance, the vulnerability of an application can depend on the block size of the kernels in the application. In some applications, we found that the silent data corruption rate can vary by as much as 8% when changing the block size of a kernel.

Reliability is an important design constraint in modern microprocessors, and one of the fundamental reliability challenges is combating the effects of transient faults. This requires extensive analysis, including significant fault modelling allow architects to make informed reliability tradeoffs. Recent data shows that multi-bit transient faults are becoming more common, increasing from 0.5% of static random-access memory (SRAM) faults in 180nm to 3.9% in 22nm. Such faults are predicted to be even more prevalent in smaller technology nodes. Therefore, accurately modeling the effects of multi-bit transient faults is increasingly important to the microprocessor design process. Architecture vulnerability factor (AVF) analysis is a method to model the effects of single-bit transient faults. In this paper, we propose a method to calculate AVFs for spatial multibittransient faults (MB-AVFs) and provide insights that can help reduce the impact of these faults. First, we describe a novel multi-bit AVF analysis approach for detected uncorrected errors (DUEs) and show how to measure DUE MB-AVFs in a performance simulator. We then extend our approach to measure silent data corruption (SDC) MB-AVFs. We find that MB-AVFs are not derivable from single-bit AVFs. We also find that larger fault modes have higher MB-AVFs. Finally, we present a case study on using MB-AVF analysis to optimize processor design, yielding SDC reductions of 86% in a GPU vector register file.