pythongh-132042: Remove resolve_slotdups() to speedup class creation (python#132156)

Co-authored-by: Victor Stinner <[email protected]>
Co-authored-by: sobolevn <[email protected]>
Co-authored-by: Kumar Aditya <[email protected]>

Author: 4 people

Include/internal/pycore_interp_structs.h

@@ -672,11 +672,6 @@ struct _Py_interp_cached_objects {
 
     /* object.__reduce__ */
     PyObject *objreduce;
-#ifndef Py_GIL_DISABLED
-    /* resolve_slotdups() */
-    PyObject *type_slots_pname;
-    pytype_slotdef *type_slots_ptrs[MAX_EQUIV];
-#endif
 
     /* TypeVar and related types */
     PyTypeObject *generic_type;

Include/internal/pycore_typeobject.h

@@ -152,6 +152,9 @@ typedef int (*_py_validate_type)(PyTypeObject *);
 extern int _PyType_Validate(PyTypeObject *ty, _py_validate_type validate, unsigned int *tp_version);
 extern int _PyType_CacheGetItemForSpecialization(PyHeapTypeObject *ht, PyObject *descriptor, uint32_t tp_version);
 
+// Precalculates count of non-unique slots and fills wrapperbase.name_count.
+extern int _PyType_InitSlotDefs(PyInterpreterState *interp);
+
 #ifdef __cplusplus
 }
 #endif

Misc/NEWS.d/next/Core_and_Builtins/2025-04-10-01-52-42.gh-issue-132042.fePwlj.rst

@@ -0,0 +1,2 @@
+Improve class creation times by up to 12% by pre-computing type slots
+just once. Patch by Sergey Miryanov.

Objects/typeobject.c

@@ -11422,6 +11422,11 @@ static pytype_slotdef slotdefs[] = {
     {NULL}
 };
 
+/* Stores the number of times where slotdefs has elements with same name.
+   This counter precalculated by _PyType_InitSlotDefs() when the main
+   interpreter starts. */
+static uint8_t slotdefs_name_counts[Py_ARRAY_LENGTH(slotdefs)];
+
 /* Given a type pointer and an offset gotten from a slotdef entry, return a
    pointer to the actual slot.  This is not quite the same as simply adding
    the offset to the type pointer, since it takes care to indirect through the
@@ -11464,61 +11469,6 @@ slotptr(PyTypeObject *type, int ioffset)
     return (void **)ptr;
 }
 
-/* Return a slot pointer for a given name, but ONLY if the attribute has
-   exactly one slot function.  The name must be an interned string. */
-static void **
-resolve_slotdups(PyTypeObject *type, PyObject *name)
-{
-    /* XXX Maybe this could be optimized more -- but is it worth it? */
-
-#ifdef Py_GIL_DISABLED
-    pytype_slotdef *ptrs[MAX_EQUIV];
-    pytype_slotdef **pp = ptrs;
-    /* Collect all slotdefs that match name into ptrs. */
-    for (pytype_slotdef *p = slotdefs; p->name_strobj; p++) {
-        if (p->name_strobj == name)
-            *pp++ = p;
-    }
-    *pp = NULL;
-#else
-    /* pname and ptrs act as a little cache */
-    PyInterpreterState *interp = _PyInterpreterState_GET();
-#define pname _Py_INTERP_CACHED_OBJECT(interp, type_slots_pname)
-#define ptrs _Py_INTERP_CACHED_OBJECT(interp, type_slots_ptrs)
-    pytype_slotdef *p, **pp;
-
-    if (pname != name) {
-        /* Collect all slotdefs that match name into ptrs. */
-        pname = name;
-        pp = ptrs;
-        for (p = slotdefs; p->name_strobj; p++) {
-            if (p->name_strobj == name)
-                *pp++ = p;
-        }
-        *pp = NULL;
-    }
-#endif
-
-    /* Look in all slots of the type matching the name. If exactly one of these
-       has a filled-in slot, return a pointer to that slot.
-       Otherwise, return NULL. */
-    void **res, **ptr;
-    res = NULL;
-    for (pp = ptrs; *pp; pp++) {
-        ptr = slotptr(type, (*pp)->offset);
-        if (ptr == NULL || *ptr == NULL)
-            continue;
-        if (res != NULL)
-            return NULL;
-        res = ptr;
-    }
-#ifndef Py_GIL_DISABLED
-#undef pname
-#undef ptrs
-#endif
-    return res;
-}
-
 // Return true if "name" corresponds to at least one slot definition.  This is
 // a more accurate but more expensive test compared to is_dunder_name().
 static bool
@@ -11645,7 +11595,15 @@ update_one_slot(PyTypeObject *type, pytype_slotdef *p, pytype_slotdef **next_p,
         }
         if (Py_IS_TYPE(descr, &PyWrapperDescr_Type) &&
             ((PyWrapperDescrObject *)descr)->d_base->name_strobj == p->name_strobj) {
-            void **tptr = resolve_slotdups(type, p->name_strobj);
+            void **tptr;
+            size_t index = (p - slotdefs) / sizeof(slotdefs[0]);
+            if (slotdefs_name_counts[index] == 1) {
+                tptr = slotptr(type, p->offset);
+            }
+            else {
+                tptr = NULL;
+            }
+
             if (tptr == NULL || tptr == ptr)
                 generic = p->function;
             d = (PyWrapperDescrObject *)descr;
@@ -11858,6 +11816,76 @@ update_all_slots(PyTypeObject* type)
 
 #endif
 
+int
+_PyType_InitSlotDefs(PyInterpreterState *interp)
+{
+    if (!_Py_IsMainInterpreter(interp)) {
+        return 0;
+    }
+    PyObject *bytearray = NULL;
+    PyObject *cache = PyDict_New();
+    if (!cache) {
+        return -1;
+    }
+
+    pytype_slotdef *p;
+    Py_ssize_t idx = 0;
+    for (p = slotdefs; p->name_strobj; p++, idx++) {
+        assert(idx < 255);
+
+        if (PyDict_GetItemRef(cache, p->name_strobj, &bytearray) < 0) {
+            goto error;
+        }
+
+        if (!bytearray) {
+            Py_ssize_t size = sizeof(uint8_t) * (1 + MAX_EQUIV);
+            bytearray = PyByteArray_FromStringAndSize(NULL, size);
+            if (!bytearray) {
+                goto error;
+            }
+
+            uint8_t *data = (uint8_t *)PyByteArray_AS_STRING(bytearray);
+            data[0] = 0;
+
+            if (PyDict_SetItem(cache, p->name_strobj, bytearray) < 0) {
+                goto error;
+            }
+        }
+
+        assert(PyByteArray_CheckExact(bytearray));
+        uint8_t *data = (uint8_t *)PyByteArray_AS_STRING(bytearray);
+
+        data[0] += 1;
+        assert(data[0] < MAX_EQUIV);
+
+        data[data[0]] = (uint8_t)idx;
+
+        Py_CLEAR(bytearray);
+    }
+
+    memset(slotdefs_name_counts, 0, sizeof(slotdefs_name_counts));
+
+    Py_ssize_t pos = 0;
+    PyObject *key = NULL;
+    PyObject *value = NULL;
+    while (PyDict_Next(cache, &pos, &key, &value)) {
+        uint8_t *data = (uint8_t *)PyByteArray_AS_STRING(value);
+        uint8_t n = data[0];
+        for (uint8_t i = 0; i < n; i++) {
+            uint8_t idx = data[i + 1];
+            slotdefs_name_counts[idx] = n;
+        }
+    }
+
+    Py_DECREF(cache);
+    return 0;
+
+error:
+    Py_XDECREF(bytearray);
+    Py_DECREF(cache);
+    return -1;
+}
+
 
 PyObject *
 _PyType_GetSlotWrapperNames(void)

Python/pylifecycle.c

@@ -836,6 +836,10 @@ pycore_init_builtins(PyThreadState *tstate)
     }
     interp->callable_cache.object__getattribute__ = object__getattribute__;
 
+    if (_PyType_InitSlotDefs(interp) < 0) {
+        return _PyStatus_ERR("failed to init slotdefs");
+    }
+
     if (_PyBuiltins_AddExceptions(bimod) < 0) {
         return _PyStatus_ERR("failed to add exceptions to builtins");
     }

Tools/c-analyzer/cpython/ignored.tsv

@@ -344,6 +344,8 @@ Objects/obmalloc.c	-	obmalloc_state_main	-
 Objects/obmalloc.c	-	obmalloc_state_initialized	-
 Objects/typeobject.c	-	name_op	-
 Objects/typeobject.c	-	slotdefs	-
+# It initialized only once when main interpeter starts
+Objects/typeobject.c	-	slotdefs_name_counts	-
 Objects/unicodeobject.c	-	stripfuncnames	-
 Objects/unicodeobject.c	-	utf7_category	-
 Objects/unicodeobject.c	unicode_decode_call_errorhandler_wchar	argparse	-