Accelerating Virtual Machine File Systems with TimeFS

Virtualized storage systems leverage high-performance storage devices (e.g., NVMe SSDs), log-structured block devices, and low-latency virtualization techniques (e.g., vhost) to deliver exceptional performance and meet the growing demands of modern cloud applications. However, as volume utilization increases, performance can degrade significantly due to frequent garbage collection, which undermines the full potential of vhost and NVMe SSDs.We propose a cross-layered I/O stack called TimeFS. TimeFS introduces an expiration time estimation technique, which addresses the issue of semantic isolation between the virtual machine file system and the log-structured block device. Additionally, TimeFS implements a hotness-aware data layout strategy, which organizes the data layout based on estimated expiration timestamps, thereby reducing the overhead during garbage collection. Furthermore, TimeFS introduces a bucket sort-based garbage collection algorithm, which optimizes the garbage collection process in coordination with the data layout adjustments to achieve greater efficiency. Our evaluations demonstrate that TimeFS effectively reduces garbage collection overhead, enhances garbage collection efficiency, and improves system I/O performance. We compared TimeFS with the F2FS over vhost virtualized I/O stack. TimeFS achieved performance improvements of 18%–25% in FIO write-intensive workloads and 5%–21% in Filebench, YCSB, and Mobibench workloads.