1. Dynamic Prediction of Architectural Vulnerability
Kristen Walcott, Greg Humphreys, Sudhanva Gurumurthi
University of Virginia {walcott, humper,
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 and across applications.
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.
2 SimPoints of bzip2
Rising Problem
Dynamic AVF Prediction
Outliers
(Correlation to AVF)
Intel Corporation
Microarchitectural Metrics
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.
Particle Strike
Causes Bit Flip!
Bit
Read?
yes no
Detection &
Correction
Using linear and quadratic regression, we determined an AVF characterization that uses only a few easily measurable variables. These characterizations can be used to predict AVF accurately.
Bit has error protection
benign fault
no error
benign fault
no error no
Detection
only
Does bit matter?
Does bit matter? no
yes no
yes
True Detected Unrecoverable Error
False Detected Unrecoverable Error
Silent Data Corruption
benign fault
no error
galgel benchmark
What bits matter?
Future Work
Calculating Vulnerability
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.
AVFbit = Probability that a Bit Matters =
# of Visible Errors
# of Bit Flips from Particle Strikes
Computer Science
at the UNIVERSITY of VIRGINIA