Access Interval Prediction by Partial Matching for Tightly Coupled Memory Systems

Abstract

In embedded systems, tightly coupled memories (TCMs) are usually shared between multiple masters for the purpose of hardware efficiency and software flexibility. On the one hand, memory sharing improves area utilization, but on the other hand, this can lead to a performance degradation due to an increase in access conflicts. To mitigate the associated performance penalty, access interval prediction (AIP) has been proposed. In a similar fashion to branch prediction, AIP exploits program flow regularity to predict the cycle of the next memory access. We show that this structural similarity allows for adaption of state-of-the-art branch predictors, such as Prediction by Partial Matching (PPM) and the TAgged GEometric history length (TAGE) branch predictor. Our analysis on memory access traces reveals that PPM predicts 99 percent of memory accesses. As PPM does not lend itself to hardware implementation, we also present the PPM-based TAGE access interval predictor which attains an accuracy of over 97 percent outperforming all previously presented implementable AIP schemes.