Correlation prefetching with a user-level memory thread

Yan Solihin, Jaejin Lee, Josep Torrellas

Research output: Contribution to journalArticlepeer-review


This paper proposes using a User-Level Memory Thread (ULMT) for correlation prefetching. In this approach, a user thread runs on a general-purpose processor in main memory, either in the memory controller chip or in a DRAM chip. The thread performs correlation prefetching in software, sending the prefetched data into the L2 cache of the main processor. This approach requires minimal hardware beyond the memory processor: The correlation table is a software data structure that resides in main memory, while the main processor only needs a few modifications to its L2 cache so that it can accept incoming prefetches. In addition, the approach has wide applicability, as it can effectively prefetch even for irregular applications. Finally, it is very flexible, as the prefetching algorithm can be customized by the user on an application basis. Our simulation results show that, through a new design of the correlation table and prefetching algorithm, our scheme delivers good results. Specifically, nine mostly-irregular applications show an average speedup of 1.32. Furthermore, our scheme works well in combination with a conventional processor-side sequential prefetcher, in which case the average speedup increases to 1.46. Finally, by exploiting the customization of the prefetching algorithm, we increase the average speedup to 1.53.

Original languageEnglish (US)
Pages (from-to)563-580
Number of pages18
JournalIEEE Transactions on Parallel and Distributed Systems
Issue number6
StatePublished - Jun 2003


  • Correlation prefetching
  • Helper threads
  • Heterogeneous system
  • Intelligent memory architecture
  • Memory-side prefetching
  • Prefetching
  • Processing-in-memory

ASJC Scopus subject areas

  • Signal Processing
  • Hardware and Architecture
  • Computational Theory and Mathematics

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