mSWAT: Low-cost hardware fault detection and diagnosis for multicore systems

Continued technology scaling is resulting in systems with billions of devices. Unfortunately, these devices are prone to failures from various sources, resulting in even commodity systems being affected by the growing reliability threat. Thus, traditional solutions involving high redundancy or piecemeal solutions targeting specific failure modes will no longer be viable owing to their high overheads. Recent reliability solutions have explored using low-cost monitors that watch for anomalous software behavior as a symptom of hardware faults. We previously proposed the SWAT system that uses such low-cost detectors to detect hardware faults, and a higher cost mechanism for diagnosis. However, all of the prior work in this context, including SWAT, assumes single-threaded applications and has not been demonstrated for multithreaded applications running on multicore systems. This paper presents mSWAT, the first work to apply symptom based detection and diagnosis for faults in multicore architectures running multithreaded software. For detection, we extend the symptom-based detectors in SWAT and show that they result in a very low silent data corruption (SDC) rate for both permanent and transient hardware faults. For diagnosis, the multicore environment poses significant new challenges. First, deterministic replay required for SWAT's single-threaded diagnosis incurs higher overheads for multithreaded workloads. Second, the fault may propagate to fault-free cores resulting in symptoms from fault-free cores and no available known-good core, breaking fundamental assumptions of SWAT's diagnosis algorithm. We propose a novel permanent fault diagnosis algorithm for multithreaded applications running on multicore systems that uses a lightweight isolated deterministic replay to diagnose the faulty core with no prior knowledge of a known good core. Our results show that this technique successfully diagnoses over 95% of the detected permanent faults while incurring low hardware overheads. mSWAT thus offers an affordable solution to protect future multicore systems from hardware faults.