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bpo-36012: Avoid linear slot search when it's easy to know that we are not looking for a slot name #11907

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Merged
rhettinger merged 12 commits into from
Feb 20, 2019
Merged

bpo-36012: Avoid linear slot search when it's easy to know that we are not looking for a slot name #11907

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22d7036
bpo-36012: Avoid linear slot search when it's easy to know that we ar…
scoder Feb 17, 2019
a5c0079
bpo-36012: Constrain slot name check even more to reduce false positi…
scoder Feb 17, 2019
72e318c
bpo-36012: Reduce data dependencies in slot name check to speed up th…
scoder Feb 17, 2019
cb701a5
bpo-36012: Rewrite "name_looks_like_slot()" helper function in a dens…
scoder Feb 18, 2019
3569a80
Move "PyType_Modified()" call out of "update_slot()" to avoid calling…
scoder Feb 18, 2019
15e9d0c
bpo-36012: Move "is_dunder_name()" helper function to a better place …
scoder Feb 18, 2019
64b68ac
bpo-36012: Use more common "&&" for joining comparisons instead of "&…
scoder Feb 19, 2019
5925e22
Remove unintended newline.
scoder Feb 19, 2019
9152bf7
bpo-36012: Reorder chain of conditions to place the most selective fi…
scoder Feb 19, 2019
cb6006c
Add NEWS and Whatsnew entries
rhettinger Feb 19, 2019
826fa5b
Fix trailing whitespace
rhettinger Feb 19, 2019
588f098
Test PyUnicode_CHECK_INTERNED() to bypass PyUnicode_InternInPlace() w…
rhettinger Feb 19, 2019
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5 changes: 5 additions & 0 deletions Doc/whatsnew/3.8.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -375,6 +375,11 @@ Optimizations
This makes the created list 12% smaller on average. (Contributed by
Raymond Hettinger and Pablo Galindo in :issue:`33234`.)

* Doubled the speed of class variable writes. When a non-dunder attribute
was updated, there was an unnecessary call to update slots.
(Contributed by Stefan Behnel, Pablo Galindo Salgado, Raymond Hettinger,
Comment thread
scoder marked this conversation as resolved.
Neil Schemenauer, and Serhiy Storchaka in :issue:`36012`.)


Build and C API Changes
=======================
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2019-02-19-10-47-51.bpo-36012.xq7C9E.rst
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@@ -0,0 +1,2 @@
Doubled the speed of class variable writes. When a non-dunder attribute was
updated, there was an unnecessary call to update slots.
51 changes: 38 additions & 13 deletions Objects/typeobject.c
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Expand Up @@ -3164,6 +3164,24 @@ _PyType_LookupId(PyTypeObject *type, struct _Py_Identifier *name)
return _PyType_Lookup(type, oname);
}

/* Check if the "readied" PyUnicode name
is a double-underscore special name. */
static int
is_dunder_name(PyObject *name)
{
Py_ssize_t length = PyUnicode_GET_LENGTH(name);
int kind = PyUnicode_KIND(name);
/* Special names contain at least "__x__" and are always ASCII. */
if (length > 4 && kind == PyUnicode_1BYTE_KIND) {
Py_UCS1 *characters = PyUnicode_1BYTE_DATA(name);
return (
((characters[length-2] == '_') && (characters[length-1] == '_')) &&
((characters[0] == '_') && (characters[1] == '_'))
);
}
return 0;
}

/* This is similar to PyObject_GenericGetAttr(),
but uses _PyType_Lookup() instead of just looking in type->tp_dict. */
static PyObject *
Expand Down Expand Up @@ -3275,12 +3293,14 @@ type_setattro(PyTypeObject *type, PyObject *name, PyObject *value)
if (name == NULL)
return -1;
}
PyUnicode_InternInPlace(&name);
if (!PyUnicode_CHECK_INTERNED(name)) {
PyErr_SetString(PyExc_MemoryError,
"Out of memory interning an attribute name");
Py_DECREF(name);
return -1;
PyUnicode_InternInPlace(&name);
if (!PyUnicode_CHECK_INTERNED(name)) {
PyErr_SetString(PyExc_MemoryError,
"Out of memory interning an attribute name");
Py_DECREF(name);
return -1;
}
}
}
else {
Expand All @@ -3289,7 +3309,16 @@ type_setattro(PyTypeObject *type, PyObject *name, PyObject *value)
}
res = _PyObject_GenericSetAttrWithDict((PyObject *)type, name, value, NULL);
if (res == 0) {
res = update_slot(type, name);
/* Clear the VALID_VERSION flag of 'type' and all its
subclasses. This could possibly be unified with the
update_subclasses() recursion in update_slot(), but carefully:
they each have their own conditions on which to stop
recursing into subclasses. */
PyType_Modified(type);

if (is_dunder_name(name)) {
res = update_slot(type, name);
}
assert(_PyType_CheckConsistency(type));
}
Py_DECREF(name);
Expand Down Expand Up @@ -7233,13 +7262,6 @@ update_slot(PyTypeObject *type, PyObject *name)
assert(PyUnicode_CheckExact(name));
assert(PyUnicode_CHECK_INTERNED(name));

/* Clear the VALID_VERSION flag of 'type' and all its
subclasses. This could possibly be unified with the
update_subclasses() recursion below, but carefully:
they each have their own conditions on which to stop
recursing into subclasses. */
PyType_Modified(type);

init_slotdefs();
pp = ptrs;
for (p = slotdefs; p->name; p++) {
Expand Down Expand Up @@ -7278,6 +7300,9 @@ update_all_slots(PyTypeObject* type)
{
slotdef *p;

/* Clear the VALID_VERSION flag of 'type' and all its subclasses. */
PyType_Modified(type);
Comment thread
rhettinger marked this conversation as resolved.

init_slotdefs();
for (p = slotdefs; p->name; p++) {
/* update_slot returns int but can't actually fail */
Expand Down