Off-chip prefetching based on Hidden Markov Model for non-volatile memory architectures

PLoS One. 2021 Sep 14;16(9):e0257047. doi: 10.1371/journal.pone.0257047. eCollection 2021.

Abstract

Non-volatile memory technology is now available in commodity hardware. This technology can be used as a backup memory for an external dram cache memory without needing to modify the software. However, the higher read and write latencies of non-volatile memory may exacerbate the memory wall problem. In this work we present a novel off-chip prefetch technique based on a Hidden Markov Model that specifically deals with the latency problem caused by complexity of off-chip memory access patterns. Firstly, we present a thorough analysis of off-chip memory access patterns to identify its complexity in multicore processors. Based on this study, we propose a prefetching module located in the llc which uses two small tables, and where the computational complexity of which is linear with the number of computing threads. Our Markov-based technique is able to keep track and make clustering of several simultaneous groups of memory accesses coming from multiple simultaneous threads in a multicore processor. It can quickly identify complex address groups and trigger prefetch with very high accuracy. Our simulations show an improvement of up to 76% in the hit ratio of an off-chip dram cache for multicore architecture over the conventional prefetch technique (g/dc). Also, the overhead of prefetch requests (failed prefetches) is reduced by 48% in single core simulations and by 83% in multicore simulations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benchmarking
  • Computers*
  • Markov Chains*

Grants and funding

The work was supported by the Spanish Ministry of Economy and Competitiveness (Grant No. TEC2017-84321-C4-2-R) with support from Feder Funds and also by MINECO/AEI/ERDF (EU) (grant PID2019-105660RB-C21 / AEI / 10.13039/501100011033), Aragón Government (T58_20R research group), and ERDF 2014-2020 “Construyendo Europa desde Aragón”. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.