{"id":6654,"library":"gilknocker","title":"GIL Knocker (gilknocker)","description":"gilknocker is a Python library, with core components implemented in Rust, designed to measure Global Interpreter Lock (GIL) contention in Python applications. It provides a quick and dirty metric by spawning a background thread that periodically attempts to acquire the GIL and records the time taken. This is particularly useful for identifying GIL-bound sections of code without the overhead of a full profiler like `py-spy`. The current version is 0.4.2, and it supports Python 3.9 and newer.","status":"active","version":"0.4.2","language":"en","source_language":"en","source_url":"https://github.com/milesgranger/gilknocker","tags":["performance","profiling","GIL","concurrency","python internals","rust-extension"],"install":[{"cmd":"pip install gilknocker","lang":"bash","label":"Install latest version"}],"dependencies":[],"imports":[{"symbol":"Knocker","correct":"from gilknocker import Knocker"}],"quickstart":{"code":"import time\nfrom gilknocker import Knocker\n\ndef my_gil_heavy_function():\n    # Simulate some GIL-bound work\n    _ = [i*i for i in range(1_000_000)]\n\nknocker = Knocker(\n    polling_interval_micros=1000, # How frequently to re-acquire GIL\n    sampling_interval_micros=10000, # How long to run polling routine\n    sleeping_interval_micros=100000 # How long to sleep between sampling\n)\n\nprint(\"Starting GIL contention measurement...\")\nknocker.start()\n\nmy_gil_heavy_function()\n\nknocker.stop()\nprint(\"Stopping GIL contention measurement.\")\n\nmetrics = knocker.get_metrics()\nprint(f\"Average GIL acquisition time: {metrics.avg_acquisition_time_micros:.2f} microseconds\")\nprint(f\"Max GIL acquisition time: {metrics.max_acquisition_time_micros:.2f} microseconds\")\nprint(f\"Total samples: {metrics.total_samples}\")\n","lang":"python","description":"This example demonstrates how to use the `Knocker` class to measure GIL contention during the execution of a Python function. It initializes `Knocker` with recommended default intervals, starts the measurement, runs a simulated GIL-heavy function, stops the measurement, and then prints the collected metrics."},"warnings":[{"fix":"Adjust `polling_interval_micros` and other interval parameters based on your application's sensitivity to overhead and the desired measurement granularity.","message":"The `polling_interval_micros` parameter directly impacts both the accuracy of the GIL contention measurement and the performance overhead introduced by `gilknocker`. Setting this value too low increases accuracy but can significantly slow down your program by increasing competition for the GIL. Users should experiment to find an appropriate balance, with `polling_interval_micros=1_000` often suggested as a reasonable starting point.","severity":"gotcha","affected_versions":"All versions"},{"fix":"For holistic performance debugging, integrate `gilknocker` alongside broader profiling tools.","message":"`gilknocker` is designed for quick, specific GIL contention metrics within defined code blocks. It is not intended as a replacement for comprehensive profiling tools like `py-spy` or `cProfile` for general performance analysis, as it focuses solely on GIL activity rather than overall CPU or memory usage.","severity":"gotcha","affected_versions":"All versions"},{"fix":"Monitor `gilknocker`'s release notes for compatibility updates with newer Python versions, especially those implementing GIL-related changes.","message":"The Python Global Interpreter Lock (GIL) is an evolving part of CPython. Future versions of CPython (e.g., Python 3.13+) are exploring options to make the GIL optional (as proposed by PEP 703), and Python 3.12 introduced a per-interpreter GIL. If the GIL is eventually removed or its internal behavior changes significantly in future Python releases, `gilknocker`'s core functionality may be impacted or become obsolete, requiring updates to remain compatible or relevant.","severity":"gotcha","affected_versions":"Potentially future Python 3.13+ versions"}],"env_vars":null,"last_verified":"2026-04-15T00:00:00.000Z","next_check":"2026-07-14T00:00:00.000Z","problems":[]}