Joseph Izraelevitz

Linearizability of Persistent Memory Objects Under a Full-System-Crash Failure Model

This paper provides a theoretical and practical framework for crash-resilient data structures on a machine with persistent (nonvolatile) memory but transient registers and cache. In contrast to certain prior work, but in keeping with “real world” systems, we assume a full-system failure model, in which all transient state (of all processes) is lost on a crash. We introduce the notion of durable linearizability to govern the safety of concurrent objects under this failure model and a corresponding relaxed, buffered variant which ensures that the persistent state in the event of a crash is consistent but not necessarily up to date.

Failure-Atomic Persistent Memory Updates via JUSTDO Logging

Persistent memory invites applications to manipulate persistent data via load and store instructions. Because failures during updates may destroy transient data (e.g., in CPU registers), preserving data integrity in the presence of failures requires failure-atomic bundles of updates. Prior failure atomicity approaches for persistent memory entail overheads due to logging and CPU cache flushing. Persistent caches can eliminate the need for flushing, but conventional logging remains complex and memory intensive. We present the design and implementation of JUSTDO logging, a new failure atomicity mechanism that greatly reduces the memory footprint of logs, simplifies log management, and enables fast parallel recovery following failure. Crash-injection tests confirm that JUSTDO logging preserves application data integrity and performance evaluations show that it improves throughput 3x or more compared with a state-of-the-art alternative for a spectrum of data-intensive algorithms.

Brief announcement: fast dual ring queues

In this paper, we introduce two new FIFO dual queues. Like all dual queues, they arrange for dequeue operations to block when the queue is empty, and to complete in the original order when data becomes available. Compared to alternatives in which dequeues on an empty queue return an error code and force the caller to retry, dual queues provide a valuable guarantee of fairness. Our algorithms, based on the LCRQ of Morrison and Afek, outperform existing dual queues - notably the one in java.util.concurrent - by a factor of four to six. For both of our algorithms, we present extensions that guarantee lock freedom, albeit at some cost in performance.

Brief announcement: a generic construction for nonblocking dual containers

A dual container has the property that when it is empty, the remove method will insert an explicit reservation (antidata) into the container, rather than returning an error flag. This convention gives the container explicit control over the order in which pending requests will be satisfied once data becomes available. The dual pattern also allows the methods caller to spin on a thread-local flag, avoiding memory contention. In this paper we introduce a new nonblocking construction that allows any nonblocking container for data to be paired with almost any nonblocking container for antidata. This construction provides a composite ordering discipline - e.g., it can satisfy pending pops from a stack in FIFO order, or satisfy pending dequeues in order of thread priority.

Generality and Speed in Nonblocking Dual Containers

Nonblocking dual data structures extend traditional notions of nonblocking progress to accommodate partial methods, both by bounding the number of steps that a thread can execute after its preconditions have been satisfied and by ensuring that a waiting thread performs no remote memory accesses that could interfere with the execution of other threads. A nonblocking dual container, in particular, is designed to hold either data or requests. An insert operation either adds data to the container or removes and satisfies a request; a remove operation either takes data out of the container or inserts a request. We present the first general-purpose construction for nonblocking dual containers, allowing any nonblocking container for data to be paired with almost any nonblocking container for requests. We also present new custom algorithms, based on the LCRQ of Morrison and Afek, that outperform the fastest previously known dual containers by factors of four to six.

An Unbounded Nonblocking Double-Ended Queue

We introduce a new algorithm for an unbounded concurrent double-ended queue (deque). Like the bounded deque of Herlihy, Luchangco, and Moir on which it is based, the new algorithm is simple and obstruction free, has no pathological long-latency scenarios, avoids interference between operations at opposite ends, and requires no special hardware support beyond the usual compare-and-swap. To the best of our knowledge, no prior concurrent deque combines these properties with unbounded capacity, or provides consistently better performance across a wide range of concurrent workloads.