Transactional memory support for scalable and transparent parallelization of multiplayer games

In this paper, we study parallelization of multiplayer games using software Transactional Memory (STM) support. We show that the STM provides not only ease of programming, but also better performance than that achievable with state-of-the-art lock-based programming, for this realistic high impact application. For this purpose, we use a game benchmark, SynQuake, that extracts the main data structures and the essential features of the popular game Quake. SynQuake can be driven with a synthetic workload generator that flexibly emulates client game actions and various hot-spot scenarios in the game world. We implement, evaluate and compare the STM version of SynQuake with a state-of-the-art lock-based parallelization of Quake, which we ported to SynQuake. While in STM-SynQuake support for maintaining the consistency of each complex game action is automatic, conservative locking of surrounding objects within a bounding box, for the duration of the game action is inherently needed in lock-based SynQuake. This leads to higher scalability of STM-SynQuake versus lock-based SynQuake, due to a higher degree of false sharing in the latter. Task assignment to threads has a second-order effect on the scalability of STM-SynQuake, due to its impact on the application's true sharing patterns. We show that a dynamic locality-aware task assignment to threads provides the best trade-off between load balancing and conflict reduction.