SPB: Towards Low-Latency CXL Memory via Speculative Protocol Bypassing

Compute Express Link (CXL) is an advanced inter-connect standard designed to facilitate high-speed communication between CPUs, accelerators, and memory devices, making it well-suited for data-intensive applications such as machine learning and real-time analytics. Despite its advantages, CXL memory encounters significant latency challenges due to the complex hierarchy of protocol layers, which can adversely impact performance in latency-sensitive scenarios. To address this issue, we introduce the Speculative Protocol Bypassing (SPB) architecture, which aims to minimize latency during read operations by speculatively bypassing several protocol layers of CXL. To achieve this, SPB employs the Snooper mechanism, which extracts essential read commands from the packet data at an early stage, allowing it to bypass multiple protocol layers and reduce memory access time. Additionally, the Hazard Filter (HF) prevents Read-After-Write (RAW) hazards between read and write operations, thereby maintaining data integrity and ensuring system reliability. The SPB architecture effectively optimizes CXL memory access latency, providing a robust solution for high-performance computing environments that require low latency as well as high efficiency. Its minimal hardware overhead makes it a practical and scalable enhancement for future CXL-based memory.