  In today's data centers, personalized recommendation systems face challenges
such as the need for large memory capacity and high bandwidth, especially when
performing embedding operations. Previous approaches have relied on DIMM-based
near-memory processing techniques or introduced 3D-stacked DRAM to address
memory-bound issues and expand memory bandwidth. However, these solutions fall
short when dealing with the expanding size of personalized recommendation
systems. Recommendation models have grown to sizes exceeding tens of terabytes,
making them challenging to run efficiently on traditional single-node inference
servers. Although various algorithmic methods have been proposed to reduce
embedding table capacity, they often result in increased memory access or
inefficient utilization of memory resources. This paper introduces HEAM, a
heterogeneous memory architecture that integrates 3D-stacked DRAM with DIMM to
accelerate recommendation systems in which compositional embedding is
utilized-a technique aimed at reducing the size of embedding tables. The
architecture is organized into a three-tier memory hierarchy consisting of
conventional DIMM, 3D-stacked DRAM with a base die-level Processing-In-Memory
(PIM), and a bank group-level PIM incorporating lookup tables. This setup is
specifically designed to accommodate the unique aspects of compositional
embedding, such as temporal locality and embedding table capacity. This design
effectively reduces bank access, improves access efficiency, and enhances
overall throughput, resulting in a 6.3 times speedup and 58.9% energy savings
compared to the baseline.
