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diff --git a/Doc/glossary.rst b/Doc/glossary.rst index 32ad8e3..9ec61de 100644 --- a/Doc/glossary.rst +++ b/Doc/glossary.rst @@ -102,9 +102,10 @@ Glossary See :pep:`343`. CPython - The canonical implementation of the Python programming language. The - term "CPython" is used in contexts when necessary to distinguish this - implementation from others such as Jython or IronPython. + The canonical implementation of the Python programming language, as + distributed on `python.org <http://python.org>`_. The term "CPython" + is used when necessary to distinguish this implementation from others + such as Jython or IronPython. decorator A function returning another function, usually applied as a function @@ -263,16 +264,25 @@ Glossary See :term:`global interpreter lock`. global interpreter lock - The lock used by Python threads to assure that only one thread - executes in the :term:`CPython` :term:`virtual machine` at a time. - This simplifies the CPython implementation by assuring that no two - processes can access the same memory at the same time. Locking the - entire interpreter makes it easier for the interpreter to be - multi-threaded, at the expense of much of the parallelism afforded by - multi-processor machines. Efforts have been made in the past to - create a "free-threaded" interpreter (one which locks shared data at a - much finer granularity), but so far none have been successful because - performance suffered in the common single-processor case. + The mechanism used by the :term:`CPython` interpreter to assure that + only one thread executes Python :term:`bytecode` at a time. + This simplifies the CPython implementation by making the object model + (including critical built-in types such as :class:`dict`) implicitly + safe against concurrent access. Locking the entire interpreter + makes it easier for the interpreter to be multi-threaded, at the + expense of much of the parallelism afforded by multi-processor + machines. + + However, some extension modules, either standard or third-party, + are designed so as to release the GIL when doing computationally-intensive + tasks such as compression or hashing. Also, the GIL is always released + when doing I/O. + + Past efforts to create a "free-threaded" interpreter (one which locks + shared data at a much finer granularity) have not been successful + because performance suffered in the common single-processor case. It + is believed that overcoming this performance issue would make the + implementation much more complicated and therefore costlier to maintain. hashable An object is *hashable* if it has a hash value which never changes during |