Montage: A General System for Buffered Durably Linearizable Data Structures

TL;DR

Montage is a novel system that enables efficient, buffered durably linearizable persistent data structures using nonvolatile memory, minimizing write-back overhead and ensuring data consistency across crashes.

Contribution

It introduces a general-purpose approach and system, Montage, for building buffered durably linearizable data structures with minimal persistence overhead.

Findings

Unprecedented throughput for persistent queues, sets, and graphs

Effective minimal data persistence after crashes

Correctness of the Montage system

Abstract

The recent emergence of fast, dense, nonvolatile main memory suggests that certain long-lived data might remain in its natural pointer-rich format across program runs and hardware reboots. Operations on such data must be instrumented with explicit write-back and fence instructions to ensure consistency in the wake of a crash. Techniques to minimize the cost of this instrumentation are an active topic of research. We present what we believe to be the first general-purpose approach to building buffered durably linearizable persistent data structures, and a system, Montage, to support that approach. Montage is built on top of the Ralloc nonblocking persistent allocator. It employs a slow-ticking epoch clock, and ensures that no operation appears to span an epoch boundary. It also arranges to persist only that data minimally required to reconstruct the structure after a crash. If a crash occurs in epoch $e$, all work performed in epochs $e$ and $e-1$ is lost, but work from prior epochs is preserved. We describe the implementation of Montage, argue its correctness, and report unprecedented throughput for persistent queues, sets/mappings, and general graphs.