[Python-3000] the future of the GIL (original) (raw)

Talin talin at acm.org
Thu May 10 04:21:34 CEST 2007

Greg Ewing wrote:

Giovanni Bajo wrote:

using multiple processes cause some headaches with frozen distributions (PyInstaller, py2exe, etc.), like those usually found on Windows, specifically because Windows does not have fork(). Isn't that just a problem with Windows generally? I don't see what the method of packaging has to do with it. Also, I've seen it suggested that there may actually be a way of doing something equivalent to a fork in Windows, even though it doesn't have a fork() system call as such. Does anyone know more about this?

I also wonder about embedded systems and game consoles. I don't know how many embedded microprocessors support fork(), but I know that modern consoles such as PS/3 and Xbox do not, since they have no support for virtual memory at all.

Also remember that the PS/3 is supposed to be one of the poster children for multiprocessing -- the whole 'cell processor' thing. You can't write an efficient game on the PS/3 unless it uses multiple processors.

Admittedly, not many current console-based games use Python, but that need not always be the case in the future, and a number of PC-based games are using it already.

This much I agree: There's no point in talking about supporting multiple processors using threads as long as we're living in a refcounting world.

Thought experiment: Suppose you were writing and brand-new dynamic language today, designed to work efficiently on multi-processor systems. Forget all of Python's legacy implementation details such as GILs and refcounts and such. What would it look like, and how well would it perform? (And I don't mean purely functional languages a la Erlang.)

For example, in a language that is based on continuations at a very deep level, there need not be any "global interpreter" at all. Each separate flow of execution is merely a pointer to a call frame, the evaluation of which produces a pointer to another call frame (or perhaps the same one). Yes, there would still be some shared state that would have to be managed, but I wouldn't think that the performance penalty of managing that would be horrible.

-- Talin

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