Combining software and hardware monitoring for improved power and performance tuning

By anticipating when resources will be idle, it is possible to reconfigure the hardware to reduce power consumption without significantly reducing performance. This requires predicting what the resource requirements will be for an application. In the past, researchers have taken one of two approaches: design hardware monitors that can measure recent performance, or profile the application to determine the most likely behavior for each block of code. This paper explores a third option which is to combine hardware monitoring with software profiling to achieve lower power utilization than either method alone. We demonstrate the potential for this approach in two ways. First, we compare hardware monitoring and software profiling of IPC for code blocks and show that they capture different information. By combining them, we can control issue width and ALU usage more effectively to save more power. Second, we show that anticipating stalls due to critical load misses in the L2 cache can enable fetch halting. Again, hardware monitoring and software profiling must be used together to effectively predict misses and criticality of loads.