Distributed Logless Atomic Durability with Persistent Memory

Datacenter operators have started deploying Persistent Memory (PM), leveraging its combination of fast access and persistence for significant performance gains. A key challenge for PM-aware software is to maintain high performance while achieving atomic durability. The latter typically requires the use of logging, which introduces considerable overhead with additional CPU cycles, write traffic, and ordering requirements. In this paper, we exploit the data multiversioning inherent in the memory hierarchy to achieve atomic durability without logging. Our design, LAD, relies on persistent buffering space at the memory controllers (MCs)—already present in modern CPUs—to speculatively accumulate all of a transaction’s updates before they are all atomically committed to PM. LAD employs an on-chip distributed commit protocol in hardware to manage the distributed speculative state each transaction accumulates across multiple MCs. We demonstrate that LAD is a practical design relying on modest hardware modifications to provide atomically durable transactions, while delivering up to 80% of ideal—i.e., PM-oblivious software’s—performance.