FSR: A host-storage collaborative mechanism for data path optimization of NDP operations.

Emerging computational SSDs are becoming attractive solutions to boost the energy efficiency and performance of data-intensive applications. Such computational SSDs take advantage of the in-storage Near-Data Processing (NDP) architecture that offloads computing tasks to the storage. However, existing NDP-based applications still depend on the host to search the requested file of NDP tasks, which incurs large overhead for moving data between the host and the storage. In this paper, we propose to optimize the data path of NDP-based applications by a host-storage collaborative mechanism called File Semantics Retriever (FSR). The key idea of FSR is to realize the file system layout and the metadata structures in the storage with the collaboration of a library in the host and a handler in the firmware of the computational SSD. FSR can directly locate and fetch the requested file data in the computational SSD. Moreover, we construct a performance model to understand the suitable scenarios of FSR and the appropriate timing for using FSR. We implement and evaluate FSR on a real computational SSD platform. Extensive experimental results show that FSR can reduce the execution time of real-world NDP operations by 54.0% over existing computational SSDs relying on the host-based data path.