gilknocker 0.2.0

Knock on the Python GIL, determine how busy it is.

GIL Knocker

pip install gilknocker

When you thought the GIL was available, and you find yourself suspecting it might be spending time with another.

You probably want py-spy, however if you're looking for a quick-and-dirty way to slip in a GIL contention metric within a specific chunk of code, this might help you.

How?

Unfortunately, there doesn't appear to be any explicit C-API for checking how busy the GIL is. PyGILState_Check won't really work, that's limited to the current thread. PyInterpreterState is an opaque struct, and the PyRuntimeState and other goodies are private in CPython.

So, in ~200 lines of Rusty code, I've conjured up a basic metric that seems to align with what is reported by py-spy when running the same test case. This works by spawning a thread which, at regular intervals, re-acquires the GIL and checks how long it took for the GIL to answer.

Note, the interval (interval_micros) is configurable. The lower the value, the more accurate the metric, but will be more likely to cause a deadlock and/or slow your program down.. because it will play a larger role in competing for the GIL's attention.

Use

Look at the tests

from gilknocker import KnockKnock

knocker = KnockKnock(interval_micros=1000, timeout_secs=1)
knocker.start()

... smart code here ...

knocker.stop()
knocker.contention_metric  # float between 0-1 indicating roughly how busy the GIL was.

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License

Unlicense or MIT, at your discretion.