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The first year of free-threaded Python

(labs.quansight.org)
261 points rbanffy | 1 comments | 16 May 25 09:42 UTC | HN request time: 0.204s | source
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pansa2 ◴[16 May 25 11:38 UTC] No.44004148[source]▶
Does removal of the GIL have any other effects on multi-threaded Python code (other than allowing it to run in parallel)?

My understanding is that the GIL has lasted this long not because multi-threaded Python depends on it, but because removing it:

- Complicates the implementation of the interpreter

- Complicates C extensions, and

- Causes single-threaded code to run slower

Multi-threaded Python code already has to assume that it can be pre-empted on the boundary between any two bytecode instructions. Does free-threaded Python provide the same guarantees, or does it require multi-threaded Python to be written differently, e.g. to use additional locks?

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1. jacob019 ◴[16 May 25 12:02 UTC] No.44004386[source]▶
Your understanding is correct. You can use all the cores but it's much slower per thread and existing libraries may need to be reworked. I tried it with PyTorch, it used 10x more CPU to do half the work. I expect these issues to improve, still great to see after 20 years wishing for it.