So you want to do RDMA programming? RTRS: An easy to use, reliable high speed transport library over RDMA#

Haris, Jinpu Wang

• Why: RDMA programming is notoriously harder than sockets, yet it's now the default fabric for AI training and lossless DC workloads. RTRS is battle-tested infrastructure (5,000+ servers) that hides most of that complexity.
• What: A reliable high-speed transport library over RDMA, already in the mainline kernel (drivers/infiniband/ulp/rtrs as of v6.17.7), presenting a socket-like abstraction with production-grade reliability features.
• How: Establishes stateful sessions with heartbeats and multipath (selectable policies) with I/O failover and load balancing; sizes the connection count to CPU count with IRQ pinning for data transfers; accepts scatter-gather lists directly; and pre-allocates/pre-maps DMA buffers on the server side to shorten the data path.
• Where applicable: Building blocks for any module that wants RDMA without verbs-level expertise — the speakers call out ML/AI training as a beneficiary of the pre-mapping work. Being an in-tree kernel ULP, it constrains you to its session model. (The event page adds nothing beyond the abstract, which this write-up is based on.)