ePVF: An Enhanced Program Vulnerability Factor Methodology for Cross-Layer Resilience Analysis

The Program Vulnerability Factor (PVF) has been proposed as a metric to understand the impact of hardware faults on software. The PVF is calculated by identifying the program bits required for architecturally correct execution (ACE bits). PVF, however, is conservative as it assumes that all erroneous executions are a major concern, not just those that result in silent data corruptions, and it also does not account for errorsthat are detected at runtime, i.e., lead to program crashes. A more discriminating metric can inform the choice of the appropriate resilience techniques with acceptable performance and energy overheads. This paper proposes ePVF, an enhancement of the original PVF methodology, which filters out the crash-causing bits from the ACE bits identified by the traditional PVF analysis. The ePVF methodology consists of an error propagation model that reasons about error propagation in the program, and a crash model that encapsulates the platform-specific characteristics for handling hardware exceptions. ePVF reduces the vulnerable bits estimated by the original PVF analysis by between 45% and 67% depending on the benchmark, and has high accuracy (89% recall, 92% precision) in identifying the crash-causing bits. We demonstrate the utility of ePVF by using it to inform selectiveprotection of the most SDC-prone instructions in a program.