dimberman commented on issue #5788: [POC] multi-threading using asyncio URL: https://github.com/apache/airflow/pull/5788#issuecomment-570361064 @a > > @ash recently made some changes to the LocalExecutor to use os.fork instead of processes, this makes the multithreading in the LocalExecutor much faster and lighter weight. > > That's curious. AFAIK, `os.fork` is a child process, not a thread. In python, the GIL effectively makes all threading run with preemptive scheduling as though it is running in a single thread and the performance gains are almost none and sometimes it can hurt performance because the system threads start thrashing to get a hold of the GIL. The threads do not run in parallel because of the GIL, so parallel performance requires multiprocessing with a process pool. I recently delved into a good article on this topic, with a lot of good references for more details: > > * https://realpython.com/async-io-python > * https://realpython.com/python-gil/ > * plus links to talks by David Beazley and the gilectomy etc. @ashb perhaps you could speak to this better than I can?
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