Pyriscope: Precise and Low-Overhead Python Control Flow Tracing via Sparse Hardware-Based Events

Capturing the control-flow and/or coverage profiles of Python code becomes a pressing need for Python development community, which is commonly used in a wide spectrum of tasks including program testing/fuzzing, debugging, understanding, and optimizations. Existing tracing approaches either suffer from prohibitively high overhead or only collect approximate information, which cannot satisfy the practical requirements. In this paper, we propose to leverage modern hardware tracing modules to achieve precise and low-overhead control-flow tracing for Python programs. To this goal, we develop Pyriscope on top of CPython runtime by integrating the effective trace pruning and efficient analysis techniques. Evaluation results demonstrate the efficacy of our system. It incurs an average overhead of only 2.99% for rich-informative control-flow tracing, which is orders of magnitude smaller than that of the state of the arts.