Locality-Aware Cache Replacement Policy for Graph Traversals

Many graph processing applications consist of read-only workloads that need to perform low-latency traversals over large graphs. These traversals are inherently expensive, and storage and processing systems need to be optimized for them. The performance of secondary storage-based systems can be improved by caching locality-driven data in memory. Exploring the data reuse of graph objects in applications is important to decrease the page faults in the cache. However, graph applications can suffer from poor access locality, making caching of graph data challenging. Locality can be imposed through graph ordering algorithms that can be exploited by cache replacement algorithms. We propose a graph locality-aware cache replacement policy called LAC that exploits the serialization layout obtained by graph ordering techniques. We show that the spatial locality that is captured on disk pages offers temporal locality for subsequent accesses of cache pages, and this information can be used to make improved cache replacement decisions. We evaluate LAC against the popular GCLOCK algorithm for input graphs with different structural properties while running various query types. Our evaluation shows that LAC can outperform GCLOCK through page fault improvements by reducing latency up to 1.42X in simulation studies and up to 1.23X with integration into the Neo4j system.