Transaction Execution Models in Partially Replicated Transactional Memory: The Case for Data-Flow and Control-Flow

Abstract

In this chapter we describe solutions for managing concurrency of distributed transactional memory accesses in partially replicated deployments. A system is classified as partially replicated if, for each shared object, there is more than one node responsible for storing the object, thus resulting in multiple copies available in the system. In contrast to full replication, where all objects are replicated on all nodes, partial replication allows storing a huge amount of data that, by nature, cannot fit in a single node and improving scalability by (significantly) increasing the number of node serving transaction requests. Solutions that assume partially replicated deployments are categorized according to the mobility of shared objects. In the control-flow approach shared objects are pinned to nodes for the entire system’s lifetime, whereas in the data-flow objects are allowed to change residence node (also called owner) whenever a transaction commits a new version of the object. Intuitively, adopting the data-flow model, objects follow committing transactions whereas, relying on the control-flow model, transactions’ flow is routed towards objects. There is a number of key factors to be evaluated before preferring one transaction execution model to another. This chapter surveys all of them and provides solutions suited for different deployments. The chapter aims for helping designers to understand the execution model that better fits their requirements.