Efficient Logging in Non-Volatile Memory by Exploiting Coherency Protocols

TL;DR

This paper introduces an efficient logging protocol for non-volatile memory that leverages cache coherence protocols to minimize write latency, requiring only one round trip for logging and persistent set operations.

Contribution

It presents a novel logging protocol that exploits coherency protocols to reduce the number of memory round trips needed for atomic operations in NVM.

Findings

Single round trip logging protocol developed

Extended protocol supports persistent set operations

Reduces latency and computational overhead

Abstract

Non-volatile memory (NVM) technologies such as PCM, ReRAM and STT-RAM allow processors to directly write values to persistent storage at speeds that are significantly faster than previous durable media such as hard drives or SSDs. Many applications of NVM are constructed on a logging subsystem, which enables operations to appear to execute atomically and facilitates recovery from failures. Writes to NVM, however, pass through a processor's memory system, which can delay and reorder them and can impair the correctness and cost of logging algorithms. Reordering arises because of out-of-order execution in a CPU and the inter-processor cache coherence protocol. By carefully considering the properties of these reorderings, this paper develops a logging protocol that requires only one round trip to non-volatile memory while avoiding expensive computations. We show how to extend the logging protocol to building a persistent set (hash map) that also requires only a single round trip to non-volatile memory for insertion, updating, or deletion.