Detecting and Recovering from in - Core Hardware Faults

Aggressive scaling of CMOS transistors has enabled extensive system integration and building faster and more efficient systems. On the flip side, this has resulted in an increasing number of devices that fail in shipped components in-the-field for a variety of reasons including soft errors, wear-out failures, and infant mortality. The pervasiveness of the problem across a broad market demands low cost and generic reliability solutions, precluding traditional solutions that employed excessive redundancy or piecemeal solutions that address only a few failure modes. This dissertation presents SWAT (SoftWare Anomaly Treatment), a low cost resiliency solution that effectively handles hardware faults while incurring low cost during the common mode of faultfree operations. SWAT is based on two key observations about the design of resilient systems. First, only those hardware faults that affect software need to be handled and second, since the common mode of operation is fault-free, fault-free execution should incur near-zero overheads. SWAT thus uses novel zero to low cost hardware and software monitors that watch for anomalous software behavior to detect hardware faults. SWAT then relies on hardware support for checkpointing and rollback recovery. When dealing with fault recovery in the presence of I/O, we identify that existing software-level mechanisms that handle output buffering fall short. This dissertation therefore proposes a simple low-cost hardware buffer for output buffering and demonstrates that this strategy achieves high recoverability while incurring low overheads. Although not detailed in this dissertation, SWAT contains a comprehensive diagnosis procedure that is invoked in the rare event of a fault to isolate the root-cause of the fault by distinguishing between software bugs, transient hardware faults, and permanent hardware faults. Effectively, SWAT handles hardware faults uniformly as software bugs, amortizing the resiliency cost across both hardware and software reliability. The results in this dissertation show that the SWAT strategy is effective to detect and recover the