An efficient design for fast memory registration in RDMA

Abstract

Remote Direct Memory Access (RDMA) improves network bandwidth and reduces latency by eliminating unnecessary copies from network interface card to application buffers, but the communication buffer management to reduce memory registration and deregistration cost is a significant challenge to be addressed. Previous studies use pin-down cache and batched deregistration, but only simple LRU is used as a replacement algorithm to manage cache space. In this paper, we evaluate the cost of memory registration in both user and kernel spaces. Based on our analysis, we reduce the overhead of communication buffer management in two aspects simultaneously: utilize a Memory Registration Region Cache (MRRC), and optimize the RDMA communication process of clients and servers with Fast RDMA Read and Write Process (FRRWP). MRRC manages memory in terms of memory region, and replaces old memory regions according to both their sizes and recency. FRRWP overlaps memory registrations between a client and a server, and allows applications to submit RDMA write operations without being blocked by message synchronization. We compare the performance of MRRC and FRRWP with traditional RDMA operations. The results show that our new design improves the total cost of memory registrations and overall communication latency by up to 70%.