Scalene: a high-performance, high-precision CPU, GPU, and memory profiler for Python

Scalene v2.2.1

Bug Fixes

• sys.monitoring tool ID conflict with PyTorch (#1015, #1019): Fixed SIGSEGV crash when using Scalene with PyTorch Lightning on Python 3.12+. When PROFILER_ID is already claimed by another tool, Scalene now falls back to alternative tool IDs (3 or 4), or gracefully uses the legacy PyEval_SetTrace tracer.

• TensorFlow 2.21+ compatibility (#1018): Fixed compatibility with TensorFlow 2.21+ where trace.enabled changed from a callable to a bool. Scalene now applies a compatibility fix at profiler start time.

• Multiprocessing resource tracker (#1017): Fixed BrokenPipeError on NixOS with Python 3.13/3.14 when the resource tracker subprocess dies during semaphore creation. Scalene now falls back from spawn/forkserver to fork context.

• Subprocess profiling (#1013): Fixed profiling failing when Python interpreter flags (like -B or -u) precede -c or -m in subprocess invocations.

• Windows timer thread shutdown (#1012): Fixed fatal gilstate_tss_set error on Windows when the timer thread shuts down.

• Windows --on/--off support (#1010): Added support for --on and --off flags on Windows using Named Events.

• __future__ flags in exec/eval (#1008): Fixed __future__ compiler flags not being propagated in exec/eval/compile replacements.

• Windows multiprocessing (#1005, #998): Fixed spawn-mode multiprocessing Pool support on Windows, including pickle corruption and memoryview cleanup issues.

New Features

• Async-aware profiling (#1006): Added async-aware profiling support using sys.monitoring on Python 3.12+.

• C23 allocator support (#1011): Added support for C23 free_sized and free_aligned_sized functions in SampleHeap.

Other Changes

• Improved shell script portability for NixOS/Guix using #!/usr/bin/env bash
• Code formatting updates via Black

Full Changelog: https://github.com/plasma-umass/scalene/compare/v2.1.4...v2.2.1