Understanding Compute Express Link: A Cache-coherent Interconnect

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Publish Date: 
Tuesday, September 22, 2020
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Abstract: 

Compute Express Link™ (CXL™) is an industry-supported cache-coherent interconnect for processors, memory expansion, and accelerators. Datacenter architectures are evolving to support the workloads of emerging applications in Artificial Intelligence and Machine Learning that require a high-speed, low latency, cache-coherent interconnect. The CXL specification delivers breakthrough performance, while leveraging PCI Express® technology to support rapid adoption. It addresses resource sharing and cache coherency to improve performance, reduce software stack complexity, and lower overall systems costs, allowing users to focus on target workloads. Attendees will learn how CXL technology maintains a unified, coherent memory space between the CPU (host processor) and CXL devices allowing the device to expose its memory as coherent in the platform and allowing the device to directly cache coherent memory. This allows both the CPU and device to share resources for higher performance and reduced software stack complexity. In CXL, the CPU host is primarily responsible for coherency management abstracting peer device caches and CPU caches. The resulting simplified coherence model reduces the device cost, complexity and overhead traditionally associated with coherency across an I/O link.

Learning Objectives

Learn how CXL supports dynamic multiplexing between a rich set of protocols that includes I/O (CLX.io, based on PCIe®), caching (CXL.cache), and memory (CXL.mem) semantics.,Understand how CXL maintains a unified, coherent memory space between the CPU and any memory on the attached CXL device,Gain insight into the features introduced in the CXL specification