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gh-126868: Add freelist for compact int objects#126865
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1 @@ | ||
| Increase performance of :class:`int` by adding a freelist for compact ints. |
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -6,6 +6,7 @@ | ||
| #include "pycore_bitutils.h" // _Py_popcount32() | ||
| #include "pycore_initconfig.h" // _PyStatus_OK() | ||
| #include "pycore_call.h" // _PyObject_MakeTpCall | ||
| #include "pycore_freelist.h" // _Py_FREELIST_FREE, _Py_FREELIST_POP | ||
| #include "pycore_long.h" // _Py_SmallInts | ||
| #include "pycore_object.h" // _PyObject_Init() | ||
| #include "pycore_runtime.h" // _PY_NSMALLPOSINTS | ||
| @@ -42,7 +43,7 @@ static inline void | ||
| _Py_DECREF_INT(PyLongObject *op) | ||
| { | ||
| assert(PyLong_CheckExact(op)); | ||
| _Py_DECREF_SPECIALIZED((PyObject *)op, _PyLong_ExactDealloc); | ||
| } | ||
| static inline int | ||
| @@ -220,15 +221,18 @@ _PyLong_FromMedium(sdigit x) | ||
| { | ||
| assert(!IS_SMALL_INT(x)); | ||
| assert(is_medium_int(x)); | ||
| PyLongObject *v = (PyLongObject *)_Py_FREELIST_POP(PyLongObject, ints); | ||
| if (v == NULL) { | ||
| v = PyObject_Malloc(sizeof(PyLongObject)); | ||
| if (v == NULL) { | ||
| PyErr_NoMemory(); | ||
| return NULL; | ||
| } | ||
| _PyObject_Init((PyObject*)v, &PyLong_Type); | ||
| } | ||
| digit abs_x = x < 0 ? -x : x; | ||
| _PyLong_SetSignAndDigitCount(v, x<0?-1:1, 1); | ||
| v->long_value.ob_digit[0] = abs_x; | ||
| return (PyObject*)v; | ||
| } | ||
| @@ -3611,24 +3615,60 @@ long_richcompare(PyObject *self, PyObject *other, int op) | ||
| Py_RETURN_RICHCOMPARE(result, 0, op); | ||
| } | ||
| static inline int | ||
| compact_int_is_small(PyObject *self) | ||
| { | ||
| PyLongObject *pylong = (PyLongObject *)self; | ||
| assert(_PyLong_IsCompact(pylong)); | ||
| stwodigits ival = medium_value(pylong); | ||
| if (IS_SMALL_INT(ival)) { | ||
| PyLongObject *small_pylong = (PyLongObject *)get_small_int((sdigit)ival); | ||
| if (pylong == small_pylong) { | ||
| return 1; | ||
| } | ||
| } | ||
| return 0; | ||
| } | ||
| void | ||
| _PyLong_ExactDealloc(PyObject *self) | ||
| { | ||
| assert(PyLong_CheckExact(self)); | ||
| if (_PyLong_IsCompact((PyLongObject *)self)) { | ||
| #ifndef Py_GIL_DISABLED | ||
| if (compact_int_is_small(self)) { | ||
| // See PEP 683, section Accidental De-Immortalizing for details | ||
| _Py_SetImmortal(self); | ||
| return; | ||
| } | ||
| #endif | ||
| _Py_FREELIST_FREE(ints, self, PyObject_Free); | ||
There was a problem hiding this comment. I just realised that we didnt check for if it's a smallint cached value here. It should be rejected there Member There was a problem hiding this comment. Nevermind. It's not needed because (theoretically) the refcount of a smallint never hits 0 due to it being immortal, so this code will never be called on it. Can you add an assert to be safe? There was a problem hiding this comment. This also means my comment about the small ints was wrong. Could you remove that please? ContributorAuthor There was a problem hiding this comment. The comment has been adapted. If the refcount can never become zero, then the code in ContributorAuthor There was a problem hiding this comment. @Fidget-Spinner I think your first remark was right after all and we do need to check for smallints (at least in the 32-bit stable ABI build). I will add the check once there is consensus on #127120 (which might very well be the status quo) | ||
| return; | ||
| } | ||
| PyObject_Free(self); | ||
| } | ||
| static void | ||
| long_dealloc(PyObject *self) | ||
| { | ||
| assert(self); | ||
| if (_PyLong_IsCompact((PyLongObject *)self)) { | ||
| if (compact_int_is_small(self)) { | ||
| /* This should never get called, but we also don't want to SEGV if | ||
| * we accidentally decref small Ints out of existence. Instead, | ||
| * since small Ints are immortal, re-set the reference count. | ||
| * | ||
| * See PEP 683, section Accidental De-Immortalizing for details | ||
| */ | ||
| _Py_SetImmortal(self); | ||
| return; | ||
| } | ||
| if (PyLong_CheckExact(self)) { | ||
| _Py_FREELIST_FREE(ints, self, PyObject_Free); | ||
| return; | ||
| } | ||
| } | ||
| Py_TYPE(self)->tp_free(self); | ||
| } | ||
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Do you need it to be exported like that or could you live with a simple
extern? If not, can you explain which file needs this export?Uh oh!
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It's needed by the JIT on Windows, as it's used in bytecodes.c. This is a pretty common pattern in the internal C API unfortunately
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For semantic purposes, would it be better to have a macro named differently? (it would be a simple alias but it could help semantics and reviewers)