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Asked: 2026-05-13T16:37:08+00:00

While developing a Django app deployed on Apache mod_wsgi I found that in case

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While developing a Django app deployed on Apache mod_wsgi I found that in case of multithreading (Python threads; mod_wsgi processes=1 threads=8) Python won’t use all available processors. With the multiprocessing approach (mod_wsgi processes=8 threads=1) all is fine and I can load my machine at full.

So the question: is this Python behavior normal? I doubt it because using 1 process with few threads is the default mod_wsgi approach.

The system is:

2xIntel Xeon 5XXX series (8 cores (16 with hyperthreading)) on FreeBSD 7.2 AMD64 and Python 2.6.4

Thanks all for answers.
We all found that this behavior is normal because of GIL. Here is a good explanation:
http://jessenoller.com/2009/02/01/python-threads-and-the-global-interpreter-lock/
or stackoverflow GIL discussion: What is a global interpreter lock (GIL)?.

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1 Answer

  1. Editorial Team

    Will Python use all processors in thread mode? No.

    Python won’t use all available processors; is this Python behavior normal? Yes, it’s normal because of the GIL.

    For a discussion see http://mail.python.org/pipermail/python-3000/2007-May/007414.html.

    You may find that having a couple (or 4) of threads per core/process can still improve performance if there is some blocking, for example waiting for a response from the database would cause that process to block other connections otherwise.

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