I/O Scheduler using splitting mechanism for improving Real-Time performance in eMMC

抄録

Embedded MultiMedia Card (eMMC) is widely used in many real-time systems, such as in automotive applications. In embedded systems, it is common for applications to share storage resources, which creates a demand for protecting real-time processes from interference by other processes. Since eMMC lacks internal command queu- ing, the I/O scheduler becomes a critical component in ensuring performance. Under these conditions, priority-based schedulers for real-time systems have been developed, successfully protecting real-time processes. However, our ex- periments revealed that while these schedulers can handle the bandwidth load caused by a large number of small-sized I/O requests, they fail to manage the load caused by a small number of large-sized I/O requests. In such cases, tail latency of real-time process significantly worsens to levels comparable to systems without a scheduler. In this research, we propose an I/O scheduler equipped with an I/O splitting mechanism that converts a small number of large-sized I/O operations into a large number of small-sized I/O operations. Experiments demonstrated that, compared to ex- isting priority-based schedulers, this approach successfully reduced 99th percentile latency, achieving up to a 5-fold reduction in read latency and up to a 3-fold reduction in write latency.