z-READ: Towards Efficient and Transparent Zero-Copy Read

In cloud computing, I/O-intensive workloads can be co-located with other applications or virtual machines on a single physical machine. In this case, copy-based I/O (buffered I/O) can lead to severe performance interference to other memoryintensive workloads. It is because that the buffered I/O consumes memory bandwidth during memory copy even though it benefits from caching. To address this problem, many zero-copy I/O schemes have been proposed but none of them provides both 1) transparent copy avoidance through read/write system calls and 2) benefits of kernel-level caching at the same time. To this end, this paper presents z-READ, an efficient and transparent zero-copy read I/O scheme based on page remapping and copy-on-write techniques. In our scheme, we introduce several optimizations that minimize the overheads of page remapping by reducing the number of remote TLB shootdown.We implement z- READ prototype in memory management of Linux kernel 4.12.9. Our experimental results show that the performance of the colocated memory-intensive workloads can be negatively affected by I/O-intensive workloads in the case of copy-based I/O (up to 1.96x slowdown in-memory configurations) while z-READ incurs only up to 1.07x slowdown for the respective configuration.