This document describes critical performance bugs in PyCharm's pydevd_pep_669_tracing.py that cause 11-156x slowdown when debugging Python code, even when no breakpoints are set in the executing code. The fixes improve performance from 4.34 seconds to 0.28 seconds for a test script that calls a simple function 10 million times.
- Before: 4.34 seconds (no breakpoints) / 43.06 seconds (with module-level breakpoint)
- After: 0.277 seconds (no breakpoints) / 0.276 seconds (with module-level breakpoint)
- Speedup: 15x faster (no breakpoints), 156x faster (module-level breakpoint)