Profiling Support for Runtime Managed Code: Next Generation Performance Monitoring Units

Given the increase of runtime managed code environments in desktop, server, and mobile segments, agile, flexible, and accurate performance monitoring capabilities are required in order to perform wise code transformations and optimizations. Common profiling strategies, mainly based on instrumentation and current performance monitoring units (PMUs), are not adequate and new innovative designs are necessary. In this paper, we present the desired characteristics of what we call next generation PMUs and advocate for hardware/software collaborative approaches where hardware implements the profiling hooks and mechanisms and software implements the complex heuristics. We then propose a first design in which the hardware uses a small, yet flexible table to profile specific code regions and the software decides what/when/how to profile. This first design meets all required features and we aim it as the seed for future PMUs extensions to enable novel dynamic code transformations and optimizations.