SplitFS: Reducing Software Overhead in File Systems for Persistent Memory

TL;DR

SplitFS is a novel file system for persistent memory that significantly reduces software overhead by splitting responsibilities between user-space and kernel components, leading to improved application performance.

Contribution

SplitFS introduces a new split of responsibilities and a primitive called relink, enabling efficient file appends and atomic operations with reduced overhead.

Findings

Reduces software overhead by up to 4x compared to NOVA.

Increases application performance by up to 2x in benchmarks.

Supports multiple consistency modes for different applications.

Abstract

We present SplitFS, a file system for persistent memory (PM) that reduces software overhead significantly compared to state-of-the-art PM file systems. SplitFS presents a novel split of responsibilities between a user-space library file system and an existing kernel PM file system. The user-space library file system handles data operations by intercepting POSIX calls, memory-mapping the underlying file, and serving the read and overwrites using processor loads and stores. Metadata operations are handled by the kernel PM file system (ext4 DAX). SplitFS introduces a new primitive termed relink to efficiently support file appends and atomic data operations. SplitFS provides three consistency modes, which different applications can choose from, without interfering with each other. SplitFS reduces software overhead by up-to 4x compared to the NOVA PM file system, and 17x compared to ext4-DAX. On a number of micro-benchmarks and applications such as the LevelDB key-value store running the YCSB benchmark, SplitFS increases application performance by up to 2x compared to ext4 DAX and NOVA while providing similar consistency guarantees.