PIUMA: Programmable Integrated Unified Memory Architecture

Abstract: High performance large scale graph analytics are essential to timely analyze relationships in big data sets. Conventional processor architectures suffer from inefficient resource usage and bad scaling on those workloads. To enable efficient and scalable graph analysis, Intel developed the Programmable Integrated Unified Memory Architecture (PIUMA) as a part of the DARPA Hierarchical Identify Verify Exploit (HIVE) program. PIUMA consists of many multi-threaded cores, fine-grained memory and network accesses, a globally shared address space, powerful offload engines and a tightly integrated optical interconnection network. By utilizing co-packaged optical silicon photonics and extending the on-chip mesh protocol directly to the optical fabric, all PIUMA chips in a system are glued together in a large virtual die which allows for extremely low socket-to-socket latencies even as the system scales to thousands of sockets. Performance estimations project that a PIUMA node will outperform a conventional compute node by one to two orders of magnitude. Furthermore, PIUMA continues to scale across multiple nodes, which is a challenge in conventional multi-node setups. This paper presents the PIUMA architecture, and documents our experience in designing and building a prototype chip and its bring-up process. We summarize the methodology for our co-design of the architecture together with the software stack using simulation tools and FPGA emulation. These tools provided early performance estimations of realistic applications and allowed us to implement many optimizations across the hardware, compilers, libraries and applications. We built the PIUMA chip as a 316mm2 7nm FinFET CMOS die and constructed a 16-node system. PIUMA silicon has successfully powered on demonstrating key aspects of the architecture, some of which will be incorporated into future Intel products.