High-performance transaction processing in journaling file systems

Abstract

Journaling file systems provide crash-consistency to applications by keeping track of uncommitted changes in the journal area (journaling) and writing committed changes to their original area at a certain point (checkpointing). They generally use coarse-grained locking to access shared data structures and perform I/O operations by a single thread. For these reasons, journaling file systems often face the problem of lock contention and underutilization of I/O bandwidth on multi-cores with high-performance storage. To address these issues, we design journaling and checkpointing schemes that enable concurrent updates on data structures and parallelize I/O operations. We implement our schemes in EXT4/JBD2 and evaluate them on a 72-core machine with a high-performance NVMe SSD. The experimental results show that our optimized file system improves the performance by up to about 2.2x and 1.5x compared to the existing EXT4 file system and a recent scalable file system, respectively.