SHF: Small: Architecting the COSMOS:A Combined System of Optical Phase Change Memory and Optical Links

如今，使用图形处理、机器学习或隐私保护范例的数据密集型应用程序需要数百千兆字节的内存大小和每秒兆兆字节的带宽。为了支持应用程序不断增长的内存需求，动态随机存取存储器（DRAM）系统已经发展了几十年。然而，DRAM在未来将无法以高效和可扩展的方式支持这些大容量和带宽的需求。虽然有许多替代存储器技术（如相变存储器、磁存储器、电阻存储器等）的研究，但在这些技术中没有明确的赢家可以取代DRAM。此外，这些替代存储技术和DRAM都不能有效地补充硅光子链路技术，而硅光子链路技术有望在不久的将来取代处理器到存储器通信的高速电子链路。该项目旨在通过一个称为COSMOS的统一网络和内存系统，解决由有限的内存容量和带宽引起的问题，这是应用程序性能的重要限制因素。COSMOS集成了光控相变存储器（OPCM）技术和硅光子链路技术，实现了从处理器到高密度存储器的无缝高带宽访问的“一站式”解决方案。该项目不仅仅使用OPCM作为DRAM的替代品，还旨在展示OPCM作为非易失性存储器和内存中处理（PIM）设计方案的真正潜力。在更广泛的层面上，该项目旨在改善各个领域中许多社会数据驱动应用程序的性能，包括医疗保健、科学计算、交通和金融。该项目的研究目标是为COSMOS设计第一个完整的系统架构，然后在OPCM用作DRAM替代品、OPCM+DRAM组合具有持久性特性以及OPCM作为PIM场景时，通过实际应用内核展示其优势。为了实现这些雄心勃勃的目标，该项目被组织为以下三个研究重点和一个跨领域的重点。Thrust 1设计了一个使用OPCM和硅光子链路的完整系统架构，以解决以数据为中心的应用程序的内存容量和带宽需求。“推力2号”研究了COSMOS在PIM中的应用，在PIM中，存储的数据以光速处理。Thrust 3的目标是为应用程序开发人员和操作系统创建机制和方法，以对应用程序进行分析和配置，以便有效地利用COSMOS。横切推力建立了一种仿真方法，以准确评估OPCM作为DRAM替代品以及OPCM+DRAM组合和OPCM作为PIM设计的优势。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Today’s data-intensive applications that use graph processing, machine learning or privacy-preserving paradigms demand memory sizes on the order of hundreds of GigaBytes and bandwidths on the order of TeraBytes per second. To support the ever-growing memory needs of the applications, Dynamic Random Access Memory (DRAM) systems have evolved over the decades. However, DRAM will not be able to support these large-capacity and -bandwidth demands in the future in an efficient and scalable way. While there is research on a number of alternate memory technologies (such as phase-change memory, magnetic memory, resistive memory, etc.), there is no clear winner among these technologies to replace DRAM. Moreover, none of these alternate memory technologies nor DRAM efficiently complements the silicon-photonic link technology that is expected to replace high-speed electrical links for processor-to-memory communication in the near future. This project aims to address the problems arising from limited memory capacity and bandwidth, which are significant limiting factors in application performance, through a unified network and memory system called COSMOS. COSMOS integrates Optically-controlled Phase Change Memory (OPCM) technology and silicon-photonic link technology to achieve a "one-stop-shop" solution that provides seamless high-bandwidth access from the processor to a high-density memory. The project goes beyond solely using OPCM as a DRAM replacement, and aims to demonstrate the true potential of OPCM as non-volatile memory and in processing-in-memory (PIM) design scenarios. At a broader level, the project seeks to improve the performance of many societal data-driven applications in various domains, including healthcare, scientific computing, transportation, and finance.The research goals of this project are to design the first full system architecture for COSMOS, and then demonstrate its benefits using realistic application kernels, when OPCM is used as a DRAM replacement, in an OPCM+DRAM combination with persistence properties, and in OPCM as PIM scenarios. To achieve these ambitious goals, the project is organized into the following three research thrusts and a cross-cutting thrust. Thrust 1 designs a full-system architecture using OPCM and silicon-photonic links to address the memory capacity and bandwidth requirements of data-centric applications. Thrust 2 investigates the use of COSMOS for PIM, where the stored data is processed at the speed of light. Thrust 3 aims to create mechanisms and methods for application developers and the Operating System to profile and instrument applications for making effective use of COSMOS. The Cross-cutting Thrust builds a simulation methodology to accurately evaluate the benefits of OPCM as DRAM replacement as well as for combined OPCM+DRAM and OPCM as PIM designs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.