Cuckoo Hashing with Pages

TL;DR

This paper explores a variant of cuckoo hashing optimized for memory systems with large pages, demonstrating experimentally that it can achieve high load factors with minimal page accesses, thus reducing lookup costs.

Contribution

It introduces and experimentally evaluates cuckoo hashing with pages, a new approach that minimizes page accesses while maintaining high load factors, addressing practical lookup cost issues.

Findings

Nearly the same load as traditional cuckoo hashing with more choices

Most lookups require only one page access

Experimental results suggest promising practical efficiency

Abstract

Although cuckoo hashing has significant applications in both theoretical and practical settings, a relevant downside is that it requires lookups to multiple locations. In many settings, where lookups are expensive, cuckoo hashing becomes a less compelling alternative. One such standard setting is when memory is arranged in large pages, and a major cost is the number of page accesses. We propose the study of cuckoo hashing with pages, advocating approaches where each key has several possible locations, or cells, on a single page, and additional choices on a second backup page. We show experimentally that with k cell choices on one page and a single backup cell choice, one can achieve nearly the same loads as when each key has k+1 random cells to choose from, with most lookups requiring just one page access, even when keys are placed online using a simple algorithm. While our results are currently experimental, they suggest several interesting new open theoretical questions for cuckoo hashing with pages.