Progress on the Gilectomy

[Stefan Behnel]

Serhiy Storchaka schrieb am 11.06.2017 um 07:11:
> 10.06.17 15:54, Steve D'Aprano пише:
>> Larry Hastings is working on removing the GIL from CPython:
>>
>> https://lwn.net/Articles/723949/
>>
>> For those who don't know the background:
>>
>> - The GIL (Global Interpreter Lock) is used to ensure that only one piece of
>> code can update references to an object at a time.
>>
>> - The downside of the GIL is that CPython cannot take advantage of
>> multiple CPU
>> cores effectively. Hence multi-threaded code is not as fast as it could be.
>>
>> - Past attempts to remove the GIL caused unacceptable slow-downs for
>> single-threaded programs and code run on single-core CPUs.
>>
>> - And also failed to show the expected performance gains for multi-threaded
>> programs on multi-core CPUs. (There was some gain, but not much.)
>>
>>
>> Thanks Larry for your experiments on this!
> 
> And also GIL is used for guaranteeing atomicity of many operations and
> consistencity of internal structures without using additional locks. Many
> parts of the core and the stdlib would just not work correctly in
> multithread environment without GIL.

And the same applies to external extension modules. The GIL is really handy
when it comes to reasoning about safety and correctness of algorithms under
the threat of thread concurrency. Especially in native code, where the
result of an unanticipated race condition is usually a crash rather than an
exception.

Stefan