LUC: Limiting the Unintended Consequences of Power Scaling on Parallel Transaction-Oriented Workloads

Following an exhaustive set of experiments, we identify slowdowns in I/O performance that occur when processor power and frequency are increased. Our initial analyses indicate slowdowns are more likely to occur and more acute when the number of parallel I/O threads increases and the variability between runs is high. We use a micro benchmark-driven methodology to simplify isolation of the root causes of I/O performance loss. We classify the observed performance loss into two categories: file synchronization and file write delays. We introduce LUC, a runtime system to Limit the Unintended Consequences of power scaling and dynamically improve I/O performance. We demonstrate the effectiveness of the LUC system running on two platforms for two critical parallel transaction-oriented workloads including a mail server (vermeil) and online transaction processing (lotp).