CXL is the latest interconnect technology built on PCIe, providing three protocols to facilitate three distinct types of devices, each with unique capabilities. Among these devices, a CXL Type-2 device has become commercially available, followed by CXL Type-3 devices. Therefore, it is timely to understand capabilities and characteristics of the CXL Type-2 device, as well as explore suitable applications. In this work, first, we delve into three key features of a CXL Type-2 device: cache-coherent device accelerator to host memory, device accelerator to device memory, and host CPU to device memory accesses. Second, using microbenchmarks, we comprehensively characterize the latency and bandwidth of these memory accesses with a CXL Type-2 device, and then compare them with those of equivalent memory accesses with comparable devices, such as emulated CXL Type-2, CXL Type-3, and PCIe devices. Lastly, as applications that exploit the unique capabilities of a CXL Type-2 device, we propose two CXL-based Linux memory optimization features: compressed RAM cache for swap (zswap) and memory deduplication (ksm). Our evaluation shows that Redis, when running with traditional CPU-based zswap and ksm, suffers from a tail latency increase of 4.5-10.3× compared to Redis running alone. While PCIe-based zswap and ksm still experience a tail latency increase of up to 8.1×, CXL-based zswap and ksm practically eliminate the tail latency increase with faster and more efficient host-device communication than PCIe-based zswap and ksm.

Over the last decade, homogeneous multi-core processors emerged and became the de-facto approach for offering high parallelism, high performance and scalability for a wide range of platforms. We are now at an interesting juncture where several critical factors (smaller form factor devices, power challenges, need for specialization, etc) are guiding architects to consider heterogeneous chips and platforms for the next decade and beyond. Exploring heterogeneous architectures is challenging since it involves re-evaluating architecture options, OS implications and application development. In this paper, we describe these research challenges and then introduce a heterogeneous prototype platform called QuickIA that enables rapid exploration of heterogeneous architectures employing multiple generations of Intel processors for evaluating the implications of asymmetry and FPGAs to experiment with specialized processors or accelerators. We also show example case studies using the QuickIA research prototype to highlight its value in conducting heterogeneous architecture, OS and applications research.

This paper introduces a flexible, hybrid emulation platform for processor related emulation. It is based on a modern Xeon server and FPGA. With Intel processors implemented in FPGA and plugged into the Xeon server's processor socket, and with the Xeon BIOS modified to accommodate different cores, this platform is able to boot OS and run applications while interacting with the Xeon server's native hardware components. It enables researchers to do architectural changes in FPGA and quickly evaluate their effect on the whole platform. This platform is an ideal vehicle for research on processor technology, SoC architecture, reconfigurable computing, heterogeneous core architecture, etc.

Growing demand for energy-efficient, high-performance systems has resulted in the growth of innovative heterogeneous computing system architectures that use FPGAs. FPGA-based architectures enable designers to implement custom instruction streams executing on potentially thousands of compute elements. Traditionally, FPGAs have been used as compute elements on PCI devices; however, this does not allow the FPGAs to be co-processors. This paper describes a high-performance system architecture that is based on the Intel® Xeon® platform in which one or more FPGAs, acting as application accelerators, replace one or more processors in a dual/multi-processor (DP/MP) platform. The FPGA is thus connected directly to the Front Side Bus (FSB) and enjoys the same privileges as a processor, i.e., full participation in the coherency protocol, unrestricted access to system memory and to other processors via the high bandwidth, and low latency connection to the FSB. In addition, we also describe a software layer called the "Accelerator Abstraction Layer (AAL)", which provides a uniform, hardware- and/or platform-independent application interface. Applications written on AAL can be ported to multiple platforms that have different types of accelerators and the application does not have to be modified. In addition, the AAL also enables the developer/user to reprogram the FPGA on the fly (analogous to an operating system context switch) thereby utilizing the programmable nature of the FPGA. The resulting hardware/software stack creates a flexible and powerful platform for accelerator innovation and deployment.

Data centers and HPC clusters often incorporate specialized networking fabrics to satisfy system requirements. However, Ethernet's low cost and high performance are causing a shift from specialized fabrics toward standard Ethernet. Although Ethernet's low-level performance approaches that of specialized fabrics, the features that these fabrics provide such as reliable in-order delivery and flow control are implemented, in the case of Ethernet, by endpoint hardware and software. Unfortunately, current Ethernet endpoints are either slow (commodity NICs with generic TCP/IP stacks) or costly (offload engines). To address these issues, the JNIC project developed a novel Ethernet endpoint. JNIC's hardware and software were specifically designed for the requirements of high-performance communications within future data-centers and compute clusters. The architecture combines capabilities already seen in advanced network architectures with new innovations to create a comprehensive solution for scalable and high-performance Ethernet. We envision a JNIC architecture that is suitable for most in-data-center communication needs.