Exploring the Asynchrony of Slow Memory Filesystem with EasyIO

We introduce EasyIO, a new approach to explore asynchronous I/O on filesystems designed for (disaggregated) nonvolatile memories to improve CPU efficiency. EasyIO offloads expensive memory movement operations to the on-chip DMA engine and harvests the unleashed CPU cycles by transparently interleaving asynchronous I/Os with fine-grained application tasks. We further adopt a completion buffer-centric design to improve EasyIO's efficiency and schedulability; internally, orderless file operation and two-level locking are incorporated to break the serial order between file metadata and data, thus accelerating read and write operations and defusing deadlock risks. EasyIO also introduces a traffic-aware channel manager to fulfill the diverse performance goals of applications. Extensive experimental results show that, compared to conventional synchronous filesystems, EasyIO significantly reduces CPU consumption (using less than 88% of cores at most) while achieving comparable peak bandwidth; EasyIO also achieves 1.03-2.3× speedups across eight real-world applications. When achieving these goals, EasyIO exhibits higher but tolerable latencies for read operations due to the task interleaving.