Optimizing Access to Memory Pages in Software-Implemented Global Page Cache Systems

This paper is based on a dissertation “Techniques for organizing shared access to distributed memory pages in cloud computing systems” defended at the Igor Sikorsky Kyiv Polytechnic Institute in 2017. The paper describes distributed page processing in Oracle Real Application Clusters (Oracle RAC) and compares it with other well-known processing methods. The comparison includes analysis of different architectures (including shared nothing, shared disk, and replication-based architectures) in terms of SQL query processing and asserts the soundness of the distributed page approach (also known as global cache fusion) to cloud database management systems (DBMSs). As a result of analyzing the global cache fusion approach, the main drawback of Oracle RAC systems—increasing queue problem—is revealed; it causes the impossibility to process queries once their rate exceeds a certain threshold inversely proportional to the packet delivery time between nodes. To eliminate the increasing queue problem when accessing distributed pages, a new access method is proposed that introduces an additional page state—unloading state—which improves the efficiency of distributed page processing by reducing the number of transfers between nodes during hot page processing. In addition to cloud DBMSs, the proposed method can also be used in other cloud systems with page-organized distributed memory architecture.