What operations are blocked by GIL?
In hindsight, the GIL is not ideal, since it prevents multithreaded CPython programs from taking full advantage of multiprocessor systems in certain situations. Luckily, many potentially blocking or long-running operations, such as I/O, image processing, and NumPy number crunching, happen outside the GIL.
Why does GIL still exist?
Why was the GIL chosen as the solution : The GIL is simple to implement and was easily added to Python. It provides a performance increase to single-threaded programs as only one lock needs to be managed.
Why Python is not multi threaded?
Python does have built-in libraries for the most common concurrent programming constructs — multiprocessing and multithreading. The reason is, multithreading in Python is not really multithreading, due to the GIL in Python.
What is Python global interpreter lock (GIL)?
The Python Global Interpreter Lock or GIL, in simple words, is a mutex (or a lock) that allows only one thread to hold the control of the Python interpreter. This means that only one thread can be in a state of execution at any point in time.
How does Gil affect the performance of multi-threaded programs?
In the multi-threaded version the GIL prevented the CPU-bound threads from executing in parellel. The GIL does not have much impact on the performance of I/O-bound multi-threaded programs as the lock is shared between threads while they are waiting for I/O.
Why does Python starve the I/O-bound threads?
In such programs, Python’s GIL was known to starve the I/O-bound threads by not giving them a chance to acquire the GIL from CPU-bound threads. This was because of a mechanism built into Python that forced threads to release the GIL after a fixed interval of continuous use and if nobody else acquired the GIL, the same thread could continue its use.
Should threading be part of the default Gil policy for extensions?
If an extension does need to deal with a threaded environment, it explicitly opts in (by releasing the GIL). Therefore any would-be GIL replacement must provide GIL-like guarantees by default. Threading must remain opt-in for extensions. message on 2009-10-25 by Antoine Pitrou: Reworking the GIL (for 3.2)