BTS: Exploring Effects of Background Task-Aware Scheduling for Key-Value CSDs

A computational storage device (CSD) using Intel SPDK guarantees low latency and high throughput. The CSD must aid background tasks for the storage service applications (background tasks) without harming user I/O performance (foreground I/O) since the CSD is also a storage device. However, in practice, SPDK often increases foreground I/O latencies and underutilizes CPU cores in the CSD. These problems proceed from allocating foreground I/Os and background tasks to the same CPU core because SPDK processes them as the same request without distinguishing them. To tackle this, we propose a Background Task-aware Scheduler (BTS) for CSDs built using SPDK. BTS solves the following problems: (i) idle CPU cores in the CSD are not used, and (ii) the latency of foreground I/O increases due to interference with background tasks. For evaluation, we implemented a key-value interface CSD using SPDK. With BTS, the results show that idle CPUs are properly used to process background tasks by guaranteeing the low latency of foreground I/O when the background tasks are set to deduplication.