TreeSLS: A Whole-system Persistent Microkernel with Tree-structured State Checkpoint on NVM

Whole-system persistence promises simplified application deployment and near-instantaneous recovery. This can be implemented using single-level store (SLS) through periodic checkpointing of ephemeral state to persistent devices. However, traditional SLSs suffer from two main issues on checkpointing efficiency and external synchrony, which are critical for low-latency services with persistence need.

In this paper, we note that the decentralized state of microkernel-based systems can be exploited to simplify and optimize state checkpointing. To this end, we propose TreeSLS, a whole-system persistent microkernel that simplifies the whole-system state maintenance to a capability tree and a failure-resilient checkpoint manager. TreeSLS further exploits the emerging non-volatile memory to minimize checkpointing pause time by eliminating the distinction between ephemeral and persistent devices. With efficient state maintenance, TreeSLS further proposes delayed external visibility to provide transparent external synchrony with little overhead. Evaluation on microbenchmarks and real-world applications (e.g., Memcached, Redis and RocksDB) show that TreeSLS can complete a whole-system persistence in around 100 𝜇s and even take a checkpoint every 1 ms with reasonable overhead to applications.