When processing I/O requests, the current Linux kernel does not adequately consider the urgency of user-centric tasks closely related to user experience. To solve this critical problem, we developed a practical method in this study to enhance user experience in a computing environment wherein non-volatile memory express (NVMe) solid-state drives (SSDs) serve as storage devices. In our proposed scheme, I/O requests that originate from the user-centric tasks were preferentially served across various levels of queues by modifying the multi-queue block I/O layer of the Linux kernel, considering the dispatch method of NVMe SSDs. Our scheme tries to give as fast a path as possible for I/O requests from user-centric tasks among many queues with different levels. Especially, when the SSD is overburdened, it avoids the queues with many pending I/O requests and thus can significantly reduce the I/O latency of user-centric tasks. We implemented our proposed scheme in the Linux kernel and performed practical evaluations on a commercial SSD. The experimental results showed that the proposed scheme achieved significant enhancement in the launch time of five widely used applications by up to ~65%.

Differentiated I/O services for applications with their own requirements are very important for user satisfaction. Nonvolatile memory express (NVMe) solid-state drive (SSD) architecture can improve the I/O bandwidth with its numerous submission queues, but the quality of service (QoS) of each I/O request is never guaranteed. In particular, if many I/O requests are pending in the submission queues due to a bursty I/O workload, urgent I/O requests can be delayed, and consequently, the QoS requirements of applications that need fast service cannot be met. This paper presents a scheme that handles urgent I/O requests without delay even if there are many pending I/O requests. Since the pending I/O requests in the submission queues cannot be controlled by the host, the host memory buffer (HMB), which is part of the DRAM of the host that can be accessed from the controller, is used to process urgent I/O requests. Instead of sending urgent I/O requests into the SSDs through legacy I/O paths, the latency is removed by directly inserting them into the HMB. Emulator experiments demonstrated that the proposed scheme could reduce the average and tail latencies by up to 99% and 86%, respectively.