Anytest: Localizing the Root Cause of Hardware Transport Performance Anomalies
RoCEv2-based RDMA fabrics are the backbone of modern high-performance data-center workloads, yet large-scale deployments increasingly suffer transport-layer network performance anomalies (NPAs) such as throughput collapse, persistent unfairness, and latency inflation even without link failures. Localizing root causes of NPAs is one of today's hardest operational challenges: RoCEv2 transport logic is offloaded into proprietary NIC/switch hardware with limited observability; available counters miss μs-scale dynamics; and similar symptoms can originate from sender, receiver, or switch behaviors in the tightly coupled RoCEv2 system. We present Anytest, an in-situ black-box testing tool that localizes root causes of transport-layer NPAs on commodity RoCEv2 RNICs and Ethernet switches without re-cabling or hardware modification. Anytest decomposes RoCEv2 network system into logical roles and isolates the hardware under test by emulating the other roles with protocol-correct DPDK endpoints. This enables deterministic injection of transport events and μs-resolution measurements. We overcome non-trivial technical challenges to implement Anytest's DPDK-based endpoints, which realize protocol correctness while enforcing μs-level packet timing at the hardware line rate. Integrated into a trace-reproduce-localize workflow, Anytest has been deployed in production for ~1 year, reducing mean localization effort to 3.1 person-hours.