cs.virginia/~krw7c/avf.html

1. Bit Read? Bit has error protection benign fault no error benign fault no error benign fault no error Kristen Walcott, Greg Humphreys, Sudhanva Gurumurthi Does bit matter? Does bit matter? University of Virginia{walcott, humper, gurumurthi}@cs.virginia.edu False Detected Unrecoverable Error True Detected Unrecoverable Error Silent Data Corruption AVFbit = Probability Bit Matters = # of Visible Errors # of Bit Flips from Particle Strikes Particle Strike Causes Bit Flip! no yes Detection & Correction no Detection only no yes no yes Dynamic Prediction of Architectural Vulnerability n0 Challenge As soft errors become more of a problem, protection will be needed even for every day PCs. Providing total redundancy is too expensive and assumes that AVF is 100%. Our work shows that AVF varies over time. • Transient faults due to particle strikes are a key challenge in microprocessor design. • As transistor counts increase exponentially, per-chip faults are a growing burden. • Spatial and temporal redundancy techniques are used to protect against faults. • Redundancy techniques assume that any fault will result in a visible program error (i.e., the Architectural Vulnerability Factor (AVF)) is 100 percent. • Over-design can hurt performance and drain power. Rising Problem Dynamic AVF Prediction Outliers Intel Corporation FIT = Failure in Time = 1 failure in a billion hours Prediction Results We identify strong correlations between structural AVF values and a small set of processor metrics. Using linear and quadratic regression, we came up with an AVF characterization that uses only a few variables. These characterizations can be used to predict AVF accurately! What bits matter? Future Work With an accurate predictor, redundancy may be turned on only when vulnerability is high. Preliminary results show that partial redundancy provides a significant performance boost over full redundancy. Next we will perform a more rigorous exploration of the design space of partial redundant multithreading implementations and investigate redundancy toggling policies. Calculating Vulnerability Computer Science http://www.cs.virginia.edu/~krw7c/avf.html at the UNIVERSITY of VIRGINIA