ZNSage: Towards Hardware-Agnostic Swap Metadata Management on ZNS SSDs

The flash translation layer (FTL) in SSDs introduces logical-to-physical address mapping, but this mapping alters data layout, leading to performance degradation. This issue is particularly evident in the Linux swap subsystem. While SSDs offer higher performance than HDDs, traditional FTL-based SSDs fail to meet swap performance expectations due to scattered page placement. The introduction of zoned namespace (ZNS) SSDs aims to address this problem by enforcing sequential writes within predefined zones, allowing hosts to directly manage physical data layout and garbage collection. Prior work leveraged this capability to enhance swap performance but introduced severe hardware dependencies, requiring specific logical block addressing (LBA) formats and vendor-specific firmware modifications. To overcome these limitations, we propose ZNSage, a hardware-agnostic swap subsystem for ZNS SSDs. Unlike prior work, ZNSage eliminates hardware dependencies by storing logical-to-physical mapping information in system memory, enabling compatibility with any ZNS SSD. ZNSage not only improves swap performance but also optimizes garbage collection by minimizing page faults during swap zone reclamation. Ultimately, ZNSage provides a generalized and efficient swap solution for next-generation storage architectures.