LIME: A Framework for Debugging Load Imbalance in Multi-threaded Execution

Jungju Oh, Christopher J. Hughes, Guru Venkataramani, and Milos Prvulovic
Georgia Institute of Technology, USA; Intel Corporation, USA; George Washington University, USA

With the ubiquity of multi-core processors, software must make effective use of multiple cores to obtain good performance on modern hardware. One of the biggest roadblocks to this is load imbalance, or the uneven distribution of work across cores. We propose LIME, a framework for analyzing parallel programs and reporting the cause of load imbalance in application source code. This framework uses statistical techniques to pinpoint load imbalance problems stemming from both control flow issues (e.g., unequal iteration counts) and interactions between the application and hardware (e.g., unequal cache miss rates). We evaluate LIME on applications from widely used parallel benchmark suites, and show that LIME accurately reports the causes of load imbalance, their nature and origin in the code, and their relative importance.