  We present RDMAbox, a set of low level RDMA optimizations that provide better
performance than previous approaches. The optimizations are packaged in
easy-to-use kernel and user space libraries for applications and systems in
data center. We demonstrate the flexibility and effectiveness of RDMAbox by
implementing a kernel remote paging system and a user space file system using
RDMAbox. RDMAbox employs two optimization techniques. First, we suggest RDMA
request merging and chaining to further reduce the total number of I/O
operations to the RDMA NIC. The I/O merge queue at the same time functions as a
traffic regulator to enforce admission control and avoid overloading the NIC.
Second, we propose Adaptive Polling to achieve higher efficiency of polling
Work Completion than existing busy polling while maintaining the low CPU
overhead of event trigger. Our implementation of a remote paging system with
RDMAbox outperforms existing representative solutions with up to 4? throughput
improvement and up to 83% decrease in average tail latency in bigdata
workloads, and up to 83% reduction in completion time in machine learning
workloads. Our implementation of a user space file system based on RDMAbox
achieves up to 5.9? higher throughput over existing representative solutions.
