Re: GIL cpu multi core usage problem

[Gabriel Genellina]

En Mon, 09 Jun 2008 15:26:09 -0300, Pau Freixes <pf******@gmail.com>
escribió:

Surly this is a recurring theme into python dev world, but I need your
help
for confirm if the follow image it's really

http://www.milnou.net/~pfreixes/img/cpu_usage_gil_problem.png<http://www.milnou.net/%7Epfreixes/img/cpu_usage_gil_problem.png>

I'm writing a brief article for my blog and I need to make sure about the
current problem with GIL and multi core environments, this picture try to
explain with images the problem for scheduling multiple threads running
python code of same interpreter into multiple cpu cores. Can anyone
confirm
to me this picture ?

Yes, if both threads are executing pure Python code, they can't run
simultaneously.

Note that:
- C extensions (usually) release the GIL when they don't call into any
Python code
- The interpreter also releases the GIL before any I/O operation
If the process is I/O bound then the GIL is not so important, and if it's
CPU bound you may benefit from reimplementing the critical parts in C (by
example, using NumPy for a number-crunching process). Another alternative
is to use multiple processes with some form of IPC instead of multiple
threads.
These are the usual arguments against "fear of GIL". You should consider
your specific application to see if the GIL is actually a problem in your
case or not.

--
Gabriel Genellina