New submission from STINNER Victor <vstin...@redhat.com>:
On the following code, f() uses CALL_FUNCTION_EX bytecode to call g(). The
bytecode loads 'kw' variable which is a dictionary. But internally, the
dictionary is converted to a temporary tuple, and later a new dictionary is
created. Maybe the temporary tuple could be avoided?
def g(*args, **kw):
...
def f(*args, **kw):
g(*args, **kw)
In Python 3.6, before FASTCALL, CALL_FUNCTION_EX calls:
* do_call_core(): kw dict
* PyObject_Call(): kw dict
* function_call(): kw dict -> create a temporary tuple of keys and names:
(key[0], value[0], ...)
* _PyEval_EvalCodeWithName(): if CO_VARKEYWORDS, rebuild a new dictionary for
keyword arguments (**kw)
In Python master branch (future 3.8) with FASTCALL, CALL_FUNCTION_EX calls:
* do_call_core(): kw dict
* _PyFunction_FastCallDict(): kw dict -> a temporary tuple for keyword names
('kwnames') is created
* _PyEval_EvalCodeWithName(): if CO_VARKEYWORDS, rebuild a new dictionary for
keyword arguments (**kw)
To be clear: FASTCALL didn't make this specific function call (Python => Python
with **kw) worse nor better.
----------
components: Interpreter Core
messages: 321400
nosy: inada.naoki, serhiy.storchaka, vstinner
priority: normal
severity: normal
status: open
title: Python function call optimization: avoid temporary tuple to pass **kwargs
type: performance
versions: Python 3.8
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue34090>
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