  RDMA is increasingly adopted by cloud computing platforms to provide low CPU
overhead, low latency, high throughput network services. On the other hand,
however, it is still challenging for developers to realize fast deployment of
RDMA-aware applications in the datacenter, since the performance is highly
related to many lowlevel details of RDMA operations. To address this problem,
we present a simple and scalable RDMA as Service (RaaS) to mitigate the impact
of RDMA operational details. RaaS provides careful message buffer management to
improve CPU/memory utilization and improve the scalability of RDMA operations.
These optimized designs lead to simple and flexible programming model for
common and knowledgeable users. We have implemented a prototype of RaaS, named
RDMAvisor, and evaluated its performance on a cluster with a large number of
connections. Our experiment results demonstrate that RDMAvisor achieves high
throughput for thousand of connections and maintains low CPU and memory
overhead through adaptive RDMA transport selection.
