Memory Coherence Activity Prediction in Commercial Workloads

Tuesday January 25, 2005
Hamerschlag Hall D-210
4:00 pm

Stephen Somogyi
Carnegie Mellon University

Recent research indicates that prediction-based coherence optimizations offer substantial performance improvements for scientific applications in distributed shared memory multiprocessors. Important commercial applications also show sensitivity to coherence latency, which will become more acute in the future as technology scales. Together, these observations suggest the importance of investigating coherence activity prediction in the context of commercial workloads.

In this talk, I will present a trace-based Downgrade Predictor for predicting last stores to shared cache blocks prior to consumption by other processors, and a pattern-based Consumer Set Predictor for predicting subsequent readers. I will present an evaluation of these predictors on commercial workloads, show that downgrade prediction identifies 51%-94% of last stores, while consumer set prediction is ineffective for these workloads. Finally, I develop a hierarchical Downgrade Predictor that improves prediction coverage.

Stephen Somogyi is a third year graduate student in the Computer Architecture Lab at Carnegie Mellon, working with Prof. Babak Falsafi. Stephen's research revolves around the memory system of multiprocessor commercial servers. Stephen recently received his Master's degree in ECE and is continuing in the PhD program.