Hostping: Diagnosing Intra-host Network Bottlenecks in RDMA Servers.

Intra-host networking was considered robust in the RDMA (Remote Direct Memory Access) network and received little attention. However, as the RNIC (RDMA NIC) line rate increases rapidly to multi-hundred gigabits, the intra-host network becomes a potential performance bottleneck for network applications. Intra-host network bottlenecks may result in degraded intra-host bandwidth and increased intra-host latency, which can severely impact network performance. However, when intra-host bottlenecks occur, they can hardly be noticed due to the lack of a monitoring system. Furthermore, existing bottleneck diagnosis mechanisms fail to diagnose intra-host bottlenecks efficiently. In this paper, we analyze the symptom of intra-host bottlenecks based on our long-term troubleshooting experience and propose Hostping, the first bottleneck monitoring and diagnosis system dedicated to intra-host networks. The core idea of Hostping is conducting loopback tests between RNICs and endpoints within the host to measure intra-host latency and bandwidth. Hostping not only discovers intra-host bottlenecks we already knew but also reveals six bottlenecks we did not notice before.