The Implications of Shared Data Synchronization Techniques on Multi-Core Energy Efficiency

Shared data synchronization is at the heart of the multi-core revolution since it is essential for writing concurrent programs. Ideally, a synchronization technique should be able to fully exploit the available cores, leading to improved performance. However, with the growing demand for energy-efficient systems, it also needs to work within the energy and power budget of the system. In this paper, we perform a detailed study of the performance as well as energy efficiency of popular shared-data synchronization techniques on a commodity multi-core processor. We show that Software Transactional Memory (STM) systems can perform better than locks for workloads where a significant portion of the running time is spent in the critical sections. We also show how power-conserving techniques available on modern processors like C-states and clock frequency scaling impact energy consumption and performance. Finally, we compare the performance of STMs and locks under similar power budgets.