EuroPython 2018

Addressing multithreading and multiprocessing in transparent and Pythonic ways

Speaker(s) David Liu

With the increase in computing power, harnessing and controlling one’s code out of the single-threaded realm becomes an ever-increasing problem, coupled with the desire to stay in the Python layer. With the recent tools and frameworks that have been published, escaping the GIL cleanly is much easier than before, allow one’s Python code to effectively utilize multi-core and many core architectures in the most Pythonic ways possible. In this talk, learn about how to utilize static multiprocessing for process pinning, and effectively balancing thread pools with a monkey-patched import of threading modules.


Introduction to multithreading and multiprocessing in Python

  • History of multithreading+multiprocessing in Python, classic frameworks

  • Problems that can occur (oversubscription, nested parallelism issues, process hopping, pool resource on shared machines)

  • Python accessing bigger hardware over the last few years (28+ cores, etc)

When to stay in the GIL, and when to escape it

  • The advantages and safety of the GIL

  • Python-level exiting of the GIL; analysis of when to return to single-threaded, and when threading is a deceivingly bad idea

  • Accountability of frameworks that natively exit the GIL

The new multithreading and multiprocessing libraries and techniques

  • static multiprocessing module (smp) (and monkey patching of multiprocessing)

  • thread pool control with command line calls of Python ( python -m tbb -p 8)

Putting it all together

  • Examples of using static multiprocessing on a large machine to stop oversubscription

  • Example of pseudo-daemon process on 4-core machine by processor pinning

  • Thread pool control on a simple NumPy example

Summary - Best practices for using above methods to control multithreading+multiprocessing

  • What needs to be done in the space (frameworks and things that need to be exposed)

  • Problems that still exist in the area


in on Friday 27 July at 10:30 See schedule

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