General-purpose Asynchronous Periodic Checkpointing in Hybrid Memory

Non-volatile memory (NVM) is attractive because it enables us to make in-memory data structures persistent without serialization overhead. To implement persistent data structures durable against crashes, periodic checkpointing in NVM has been well studied. A remarkable technique that takes advantage of both DRAM and NVM (i.e., hybrid memory) for periodic checkpointing is mirroring with epoch-based write-address tracking. Its straightforward adoption, however, results in user thread blocking to checkpoint data structures mirrored in DRAM into NVM, from which applications suffer in throughput and responsiveness. To resolve this problem, we incorporate epoch-based versioning into this mirroring technique. The proposed method enables us to delegate checkpointing of data structures mirrored in DRAM into NVM to dedicated background threads that do not block user threads. We develop a system based on our method and evaluate it through experiments with memcached. Our system achieved +13% better throughput than an existing synchronous counterpart and such responsiveness that more than 50% of the performance of the original memcached kept for any time window of 0.5 ms in 99.83% of the entire execution.