bpo-42745: Make the type cache per-interpreter (GH-23947)

Make the type attribute lookup cache per-interpreter.

Add private _PyType_InitCache() function, called by PyInterpreterState_New().

Continue to share next_version_tag between interpreters, since static
types are still shared by interpreters.

Remove MCACHE macro: the cache is no longer disabled if the
EXPERIMENTAL_ISOLATED_SUBINTERPRETERS macro is defined.

3 files changed, 26 insertions, 1 deletions

diff --git a/Include/internal/pycore_interp.h b/Include/internal/pycore_interp.h
index 8c61802..339c2c4 100644
--- a/Include/internal/pycore_interp.h
+++ b/Include/internal/pycore_interp.h
@@ -180,6 +180,27 @@ struct atexit_state {
 };
 
 
+// Type attribute lookup cache: speed up attribute and method lookups,
+// see _PyType_Lookup().
+struct type_cache_entry {
+    unsigned int version;  // initialized from type->tp_version_tag
+    PyObject *name;        // reference to exactly a str or None
+    PyObject *value;       // borrowed reference or NULL
+};
+
+#define MCACHE_SIZE_EXP 12
+#define MCACHE_STATS 0
+
+struct type_cache {
+    struct type_cache_entry hashtable[1 << MCACHE_SIZE_EXP];
+#if MCACHE_STATS
+    size_t hits;
+    size_t misses;
+    size_t collisions;
+#endif
+};
+
+
 /* interpreter state */
 
 #define _PY_NSMALLPOSINTS           257
@@ -284,6 +305,7 @@ struct _is {
     struct _Py_exc_state exc_state;
 
     struct ast_state ast;
+    struct type_cache type_cache;
 };
 
 extern void _PyInterpreterState_ClearModules(PyInterpreterState *interp);
diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h
index edd0031..3975765 100644
--- a/Include/internal/pycore_object.h
+++ b/Include/internal/pycore_object.h
@@ -27,6 +27,9 @@ _PyType_HasFeature(PyTypeObject *type, unsigned long feature) {
     return ((type->tp_flags & feature) != 0);
 }
 
+extern void _PyType_InitCache(PyInterpreterState *interp);
+
+
 /* Inline functions trading binary compatibility for speed:
    _PyObject_Init() is the fast version of PyObject_Init(), and
    _PyObject_InitVar() is the fast version of PyObject_InitVar().
diff --git a/Include/internal/pycore_pylifecycle.h b/Include/internal/pycore_pylifecycle.h
index d1c23c8..c9e6947 100644
--- a/Include/internal/pycore_pylifecycle.h
+++ b/Include/internal/pycore_pylifecycle.h
@@ -76,7 +76,7 @@ extern void _PyExc_Fini(PyThreadState *tstate);
 extern void _PyImport_Fini(void);
 extern void _PyImport_Fini2(void);
 extern void _PyGC_Fini(PyThreadState *tstate);
-extern void _PyType_Fini(void);
+extern void _PyType_Fini(PyThreadState *tstate);
 extern void _Py_HashRandomization_Fini(void);
 extern void _PyUnicode_Fini(PyThreadState *tstate);
 extern void _PyUnicode_ClearInterned(PyThreadState *tstate);