Broad Performance Measurement Support for Asynchronous Multi-Tasking with APEX

APEX (Autonomic Performance Environment for eXascale) is a performance measurement library for distributed, asynchronous multitasking runtime systems. It provides support for both lightweight measurement and high concurrency. To support performance measurement in systems that employ user-level threading, APEX uses a dependency chain in addition to the call stack to produce traces and task dependency graphs. APEX also provides a runtime adaptation system based on the observed system performance. In this paper, we describe the evolution of APEX from its design for HPX to support an array of programming models and abstraction layers and describe some of the features that have evolved to help understand the asynchrony and high concurrency of asynchronous tasking models.