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bpo-29548: Fix some inefficient call API usage #97

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merged 4 commits into from
Feb 16, 2017
Merged

bpo-29548: Fix some inefficient call API usage #97

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4e2f6b4
Fix some inefficient call API usage
methane Feb 14, 2017
4e7d7a4
minor style fix
methane Feb 15, 2017
706f9e3
revert functools changes
methane Feb 15, 2017
044f9fd
remove unused variable. fix inconsistency between arg format and argu…
methane Feb 15, 2017
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25 changes: 6 additions & 19 deletions Modules/_functoolsmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -560,37 +560,25 @@ functools_reduce(PyObject *self, PyObject *args)
return NULL;
}

if ((args = PyTuple_New(2)) == NULL)
goto Fail;

for (;;) {
PyObject *op2;

if (args->ob_refcnt > 1) {
Py_DECREF(args);
if ((args = PyTuple_New(2)) == NULL)
goto Fail;
}

op2 = PyIter_Next(it);
PyObject *op2 = PyIter_Next(it);
if (op2 == NULL) {
if (PyErr_Occurred())
goto Fail;
break;
}
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I expect a ltitle slowdown if the function doesn't support fastcall. For example, a Python object with a call() method.

Can you please try to run a quick benchmark on the following two cases:

  • function supporting FASTCALL, like a builtin function
  • function not supporting FASTCALL

In general, I'm in favor of removing such hack, since playing with reference count can lead to complex and annoying bugs. But I would prefer to first see the cost on performances.

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# operator.add is FASTCALL C function
$ ./python -m perf timeit --compare-to $HOME/work/python/cpython/python -s  'L = [0]*10000' -s 'import functools, operator' -- 'functools.reduce(operator.add, L)'
/home/inada-n/work/python/cpython/python: ..................... 498 us +- 3 us
/home/inada-n/work/python/fix-call-usage/python: ..................... 412 us +- 8 us

Median +- std dev: [/home/inada-n/work/python/cpython/python] 498 us +- 3 us -> [/home/inada-n/work/python/fix-call-usage/python] 412 us +- 8 us: 1.21x faster (-17%)

# lambda is Python function (supports FASTCALL)
$ ./python -m perf timeit --compare-to $HOME/work/python/cpython/python -s  'L = [0]*10000' -s 'import functools' -- 'functools.reduce(lambda x,y: x, L)'
/home/inada-n/work/python/cpython/python: ..................... 831 us +- 7 us
/home/inada-n/work/python/fix-call-usage/python: ..................... 788 us +- 11 us

Median +- std dev: [/home/inada-n/work/python/cpython/python] 831 us +- 7 us -> [/home/inada-n/work/python/fix-call-usage/python] 788 us +- 11 us: 1.06x faster (-5%)

# builtin min and max doesn't support FASTCALL
$ ./python -m perf timeit --compare-to $HOME/work/python/cpython/python -s  'L = [0]*10000' -s 'import functools' -- 'functools.reduce(min, L)'
/home/inada-n/work/python/cpython/python: ..................... 1.23 ms +- 0.00 ms
/home/inada-n/work/python/fix-call-usage/python: ..................... 1.42 ms +- 0.04 ms

Median +- std dev: [/home/inada-n/work/python/cpython/python] 1.23 ms +- 0.00 ms -> [/home/inada-n/work/python/fix-call-usage/python] 1.42 ms +- 0.04 ms: 1.16x slower (+16%)


if (result == NULL)
if (result == NULL) {
result = op2;
}
else {
PyTuple_SetItem(args, 0, result);
PyTuple_SetItem(args, 1, op2);
if ((result = PyEval_CallObject(func, args)) == NULL)
PyObject *args[] = {result, op2};
if ((result = _PyObject_FastCall(func, args, 2)) == NULL) {
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Would you mind to move the assignment out of the if() please? "result = ...; if (result == NULL) ...".

goto Fail;
}
}
}

Py_DECREF(args);

if (result == NULL)
PyErr_SetString(PyExc_TypeError,
"reduce() of empty sequence with no initial value");
Expand All @@ -599,7 +587,6 @@ functools_reduce(PyObject *self, PyObject *args)
return result;

Fail:
Py_XDECREF(args);
Py_XDECREF(result);
Py_DECREF(it);
return NULL;
Expand Down
2 changes: 1 addition & 1 deletion Modules/_testcapimodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3070,7 +3070,7 @@ slot_tp_del(PyObject *self)
/* Execute __del__ method, if any. */
del = _PyObject_LookupSpecial(self, &PyId___tp_del__);
if (del != NULL) {
res = PyEval_CallObject(del, NULL);
res = _PyObject_CallNoArg(del);
if (res == NULL)
PyErr_WriteUnraisable(del);
else
Expand Down
3 changes: 1 addition & 2 deletions Modules/_threadmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -994,8 +994,7 @@ t_bootstrap(void *boot_raw)
_PyThreadState_Init(tstate);
PyEval_AcquireThread(tstate);
nb_threads++;
res = PyEval_CallObjectWithKeywords(
boot->func, boot->args, boot->keyw);
res = PyObject_Call(boot->func, boot->args, boot->keyw);
if (res == NULL) {
if (PyErr_ExceptionMatches(PyExc_SystemExit))
PyErr_Clear();
Expand Down
9 changes: 3 additions & 6 deletions Modules/_tkinter.c
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Expand Up @@ -2417,7 +2417,7 @@ PythonCmd(ClientData clientData, Tcl_Interp *interp, int argc, const char *argv[
}
PyTuple_SET_ITEM(arg, i, s);
}
res = PyEval_CallObject(func, arg);
res = PyObject_Call(func, arg, NULL);
Py_DECREF(arg);

if (res == NULL)
Expand Down Expand Up @@ -2667,10 +2667,7 @@ FileHandler(ClientData clientData, int mask)
func = data->func;
file = data->file;

arg = Py_BuildValue("(Oi)", file, (long) mask);
res = PyEval_CallObject(func, arg);
Py_DECREF(arg);

res = PyObject_CallFunction(func, "Oi", file, (long) mask);
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arg variable is no more used and can be removed, no?

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Thank you. I missed it.
Additionally, argument for "i" format should be int, not (long).

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Additionally, argument for "i" format should be int, not (long).

Right, I spotted it as well, but then I forgot to report it, sorry :-) Hopefully you fixed it!

if (res == NULL) {
errorInCmd = 1;
PyErr_Fetch(&excInCmd, &valInCmd, &trbInCmd);
Expand Down Expand Up @@ -2840,7 +2837,7 @@ TimerHandler(ClientData clientData)

ENTER_PYTHON

res = PyEval_CallObject(func, NULL);
res = _PyObject_CallNoArg(func);
Py_DECREF(func);
Py_DECREF(v); /* See Tktt_New() */

Expand Down
2 changes: 1 addition & 1 deletion Objects/abstract.c
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Expand Up @@ -1329,7 +1329,7 @@ PyNumber_Long(PyObject *o)
}
trunc_func = _PyObject_LookupSpecial(o, &PyId___trunc__);
if (trunc_func) {
result = PyEval_CallObject(trunc_func, NULL);
result = _PyObject_CallNoArg(trunc_func);
Py_DECREF(trunc_func);
if (result == NULL || PyLong_CheckExact(result)) {
return result;
Expand Down
41 changes: 14 additions & 27 deletions Objects/fileobject.c
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Expand Up @@ -49,39 +49,26 @@ PyFile_FromFd(int fd, const char *name, const char *mode, int buffering, const c
PyObject *
PyFile_GetLine(PyObject *f, int n)
{
_Py_IDENTIFIER(readline);
PyObject *result;

if (f == NULL) {
PyErr_BadInternalCall();
return NULL;
}

{
PyObject *reader;
PyObject *args;
_Py_IDENTIFIER(readline);

reader = _PyObject_GetAttrId(f, &PyId_readline);
if (reader == NULL)
return NULL;
if (n <= 0)
args = PyTuple_New(0);
else
args = Py_BuildValue("(i)", n);
if (args == NULL) {
Py_DECREF(reader);
return NULL;
}
result = PyEval_CallObject(reader, args);
Py_DECREF(reader);
Py_DECREF(args);
if (result != NULL && !PyBytes_Check(result) &&
!PyUnicode_Check(result)) {
Py_DECREF(result);
result = NULL;
PyErr_SetString(PyExc_TypeError,
"object.readline() returned non-string");
}
if (n <= 0) {
result = _PyObject_CallMethodIdObjArgs(f, &PyId_readline, NULL);
}
else {
result = _PyObject_CallMethodId(f, &PyId_readline, "i", n);
}
if (result != NULL && !PyBytes_Check(result) &&
!PyUnicode_Check(result)) {
Py_DECREF(result);
result = NULL;
PyErr_SetString(PyExc_TypeError,
"object.readline() returned non-string");
}

if (n < 0 && result != NULL && PyBytes_Check(result)) {
Expand Down Expand Up @@ -197,7 +184,7 @@ PyObject_AsFileDescriptor(PyObject *o)
}
else if ((meth = _PyObject_GetAttrId(o, &PyId_fileno)) != NULL)
{
PyObject *fno = PyEval_CallObject(meth, NULL);
PyObject *fno = _PyObject_CallNoArg(meth);
Py_DECREF(meth);
if (fno == NULL)
return -1;
Expand Down
2 changes: 1 addition & 1 deletion Objects/typeobject.c
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Expand Up @@ -4348,7 +4348,7 @@ _common_reduce(PyObject *self, int proto)
if (!copyreg)
return NULL;

res = PyEval_CallMethod(copyreg, "_reduce_ex", "(Oi)", self, proto);
res = PyObject_CallMethod(copyreg, "_reduce_ex", "Oi", self, proto);
Py_DECREF(copyreg);

return res;
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2 changes: 1 addition & 1 deletion Objects/weakrefobject.c
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Expand Up @@ -461,7 +461,7 @@ proxy_checkref(PyWeakReference *proxy)

WRAP_BINARY(proxy_getattr, PyObject_GetAttr)
WRAP_UNARY(proxy_str, PyObject_Str)
WRAP_TERNARY(proxy_call, PyEval_CallObjectWithKeywords)
WRAP_TERNARY(proxy_call, PyObject_Call)

static PyObject *
proxy_repr(PyWeakReference *proxy)
Expand Down