This patch adds a new method type (flags) METH_ARGS
(yeah, the name could be better) that is used in
PyMethodDef.  METH_ARGS means the min and max # of
arguments are specified in the PyMethodDef by adding 2
new fields.  This information can be used in ceval to
call the method.  No tuple packing/unpacking is
required since the C stack is used.
The original patch only modifies Python/bltinmodule.c.
 If the approach is desirable, Objects/*.c should be
modified and so should code in Modules/ (probably).
The benefits are:
 * faster function calls
 * simplify function call machinery by removing
METH_NOARGS, METH_O, and possibly METH_VARARGS
 * more introspection info for C functions (ie, min/max
arg count)
The primary drawback is:
 * the defn of the MethodDef (# args) is separate from
the function defn
 * potentially more error prone to write C methods???
I've measured between 13-22% speed improvement when
doing simple tests like:
  ./python ./Lib/timeit.py -v 'pow(3, 5)'
I think the difference tends to be fairly constant at
about .3 usec per loop.
I'm not sure of the effect on memory usage.  I wouldn't
expect it to be much in either direction.
Note:  This patch does not make the min/max arg count
available to Python code.  If this patch is accepted,
that seems like it should also be done.
It's possible that METH_VARARGS may not be able to go away.

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Also see,
http://mail.python.org/pipermail/python-dev/2005-January/051251.html

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Martin pointed out that chr(5.3) is mishandled by this patch
and needs to be corrected.

This appears to be a feature request that could now go into 3.2 at the earliest, or even 3.3 if it were to violate the core change moratorium. But I do not know if it even applies to the 3.x series.

I tried making this work early last year as part of Unladen Swallow, and even though I got it working and it does speed up certain builtin calls, it didn't move overall application performance at all. I believe this was due to cache effects, branch mispredicts or something else. Based on that experience, I don't believe this is really worth pursuing on its own.
That said, something like this is included in Unladen Swallow, which uses it to make direct calls to certain C functions. I'm going to close this accordingly.

messages: + msg107980

type: enhancement