Efficient lock management is critical in distributed systems with shared resources, especially in the context of enhanced computational power and reduced processing time. While numerous studies have leveraged Remote Direct Memory Access (RDMA) for distributed locking, these network-based approaches suffer from high network latency and jitter. The emergence of the Compute Express Link (CXL) protocol provides high-speed, low-latency connections between host processors and memory devices, presenting a compelling alternative for the lock system design. This paper introduces CXLock, the industry’s first distributed lock management system based on CXL 2.0 switches. CXLock decouples lock management into client-side queuing and manager-side arbitration, resolving race conditions of multiple clients without using remote atomics. To handle the lack of hardware-enforced coherency in CXL 2.0, CXLock employs a software-based coherency model that enables memory sharing across multiple hosts with cacheable and write-back attributes. CXLock is implemented and evaluated on a real rack-scale hardware platform containing a CXL switch and multiple host nodes. The results show that CXLock delivers an average throughput improvement of 3.7× over the RDMA-based solutions. Moreover, CXLock reduces the lock grant latency by up to 76% in both contention-free and contended scenarios.

The complexity of online applications is rapidly increasing, bringing more sophisticated performance anomalies in today's cloud datacenter. To fully understand application behaviors, we should obtain both inter-service communication data via RPC-level tracing and intra-service execution traces via application-level tracing to precisely reason about event causality. However, the average time overhead of existing intra-service tracing schemes on the traced applications is generally about 5-10%, possibly reaching 18% in the worst case. To realize practical intra-service tracing in shared and stressed datacenters, one must achieve extreme tracing efficiency with an overhead at the per-mille level.