[diek]

> It is not an issue for apps which spend most of the time doing I/O.

This is a common misconception that doesn't seem to be backed up by any data.

Dave Beazley did a number of performance tests with profiling, looking at GIL contention in a multi-core scenario: http://www.dabeaz.com/python/GIL.pdf

The results were that even IO-bound workloads still suffered because of the poor implementation of the GIL (details on slide 35 or so). This was an issue up until Python 3.2 (!) when a new GIL implementation was added, which he also profiled: http://www.dabeaz.com/python/NewGIL.pdf

[xapata]

Not backed up by data? Maybe because it's so easy to document that no one bothers to write about it?

Multithreaded IO-bound tasks don't care about the GIL.

Yeah the old implementations of the language were not as good as the latest. It doesn't seem right to criticize the language for problems that have already been fixed.

[diek]

"IO-bound multithreading is fine" has been the Python mantra for the last 20 years. Lo and behold, someone actually gathers some data and comes to find out that is absolutely wrong. For the last few years they've had a revamped version of the GIL, but that still has a burden of proof that can only be validated by profiling real-world applications.

A community can't make flat-out invalid claims for two decades and then expect everyone to take them at their word that everything is fine now.