Reducing energy consumption of queries in memory-resident database systems

The tremendous growth of system memories has increased the capacities and capabilities of memory-resident embedded databases, yet current embedded databases need to be tuned in order to take advantage of new memory technologies. In this paper, we study the implications of hosting memory resident databases, and propose hardware and software (query-driven) techniques to improve their performance and energy consumption. We exploit the structured organization of memories, which enables a selective mode of operation in which banks are accessed selectively. Unused banks are placed in a lower power mode based on access pattern information. We propose hardware techniques that dynamically control the memory by making the system adapt to the access patterns that arise from queries. We also propose a software (query-directed) scheme that directly modifies the queries to reduce the energy consumption by ensuring uniform bank accesses. Our results show that these optimizations could lead to at the least 40% reduction in memory energy. We also show that query-directed schemes better utilize the low-power modes, achieving up to 68% improvement.