Clear the internal lookup cache. Return the current version tag.
+ .. versionchanged:: 3.16
+ This function is now a no-op as the type cache is now implemented
+ per-type. It still returns the current version tag.
+
.. c:function:: unsigned long PyType_GetFlags(PyTypeObject* type)
Return the :c:member:`~PyTypeObject.tp_flags` member of *type*. This function is primarily
Porting to Python 3.16
----------------------
-* TODO
+* :c:func:`PyType_ClearCache` is now a no-op as the type cache is now
+ implemented per-type. It still returns the current version tag.
Deprecated C APIs
-----------------
* This function must escape to any code that can result in
* the GC being run, such as Py_DECREF. */
_Py_iteritemfunc _tp_iteritem;
+
+ void *_tp_cache;
};
#define _Py_ATTR_CACHE_UNUSED (30000) // (see tp_versions_used)
uint64_t type_cache_misses;
uint64_t type_cache_dunder_hits;
uint64_t type_cache_dunder_misses;
- uint64_t type_cache_collisions;
+ uint64_t type_cache_too_big;
+ uint64_t type_cache_invalidations;
+ uint64_t type_cache_resizes;
/* Temporary value used during GC */
uint64_t object_visits;
} ObjectStats;
};
-// 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
-#ifdef Py_GIL_DISABLED
- _PySeqLock sequence;
-#endif
- PyObject *name; // reference to exactly a str or None
- PyObject *value; // borrowed reference or NULL
-};
-
-#define MCACHE_SIZE_EXP 12
-
-struct type_cache {
- struct type_cache_entry hashtable[1 << MCACHE_SIZE_EXP];
-};
-
typedef struct {
PyTypeObject *type;
int isbuiltin;
are also some diagnostic uses for the list of weakrefs,
so we still keep it. */
PyObject *tp_weaklist;
+ /* Per-interpreter attribute lookup cache (struct type_cache *).
+ For static builtin types the cache must be per-interpreter
+ because tp_dict and the values it stores are per-interpreter. */
+ void *_tp_cache;
} managed_static_type_state;
#define TYPE_VERSION_CACHE_SIZE (1<<12) /* Must be a power of 2 */
where all those lower numbers are used for core static types. */
unsigned int next_version_tag;
- struct type_cache type_cache;
-
/* Every static builtin type is initialized for each interpreter
during its own initialization, including for the main interpreter
during global runtime initialization. This is done by calling
return ((type->tp_flags) & feature) != 0;
}
-extern void _PyType_InitCache(PyInterpreterState *interp);
-
extern PyStatus _PyObject_InitState(PyInterpreterState *interp);
extern void _PyObject_FiniState(PyInterpreterState *interp);
extern bool _PyRefchain_IsTraced(PyInterpreterState *interp, PyObject *obj);
--- /dev/null
+#ifndef PY_INTERNAL_TYPECACHE_H
+#define PY_INTERNAL_TYPECACHE_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef Py_BUILD_CORE
+# error "this header requires Py_BUILD_CORE define"
+#endif
+
+#include "pycore_stackref.h"
+
+
+#define _Py_TYPECACHE_MINSIZE (1 << 3)
+#define _Py_TYPECACHE_MAXSIZE (1 << 16)
+
+struct type_cache_entry {
+ PyObject *name; // name of the attribute or method, interned string, NULL if the entry is empty
+ PyObject *value; // borrowed reference or NULL
+};
+
+// Per-type attribute lookup cache: speed up attribute and method lookups,
+// see _PyTypeCache_Lookup().
+struct type_cache {
+ uint32_t mask; // mask for indexing into hashtable, i.e. size of hashtable is mask + 1
+ uint32_t available; // number of available entries in hashtable
+ uint32_t used; // number of used entries in hashtable
+ unsigned int version_tag; // initialized from type->tp_version_tag
+ struct type_cache_entry hashtable[_Py_TYPECACHE_MINSIZE]; // hashtable entries
+};
+
+struct _PyTypeCacheLookupResult {
+ _PyStackRef value; // value is a stack reference to the cached attribute or method, or NULL if not found
+ int cache_hit; // 1 if the cache entry is valid and matches the type's version tag, 0 otherwise
+ unsigned int version_tag; // version tag of the type when the value was cached
+};
+
+
+extern void _PyTypeCache_InitType(PyTypeObject *type);
+extern void _PyTypeCache_Insert(PyTypeObject *type, PyObject *name, PyObject *value);
+PyAPI_FUNC(struct _PyTypeCacheLookupResult) _PyTypeCache_Lookup(PyTypeObject *type, PyObject *name);
+PyAPI_FUNC(void) _PyTypeCache_Invalidate(PyTypeObject *type);
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* PY_INTERNAL_TYPECACHE_H */
extern void _PyTypes_FiniTypes(PyInterpreterState *);
extern void _PyTypes_FiniExtTypes(PyInterpreterState *interp);
extern void _PyTypes_Fini(PyInterpreterState *);
-extern void _PyTypes_AfterFork(void);
extern void _PyTypes_FiniCachedDescriptors(PyInterpreterState *);
static inline PyObject **
from concurrent.futures import ThreadPoolExecutor
from threading import Barrier, Thread
from unittest import TestCase
+import sys
+from test.support import import_helper, threading_helper
-from test.support import threading_helper
+_testinternalcapi = import_helper.import_module("_testinternalcapi")
self.run_one(writer_func, reader_func)
+ def test_attr_cache_mortal(self):
+ class C:
+ x = object()
+
+ class D(C):
+ pass
+
+ def writer_func():
+ for _ in range(3000):
+ C.x = object()
+
+ def reader_func():
+ for _ in range(3000):
+ C.x
+ D.x
+
+ self.run_one(writer_func, reader_func)
+
def test___class___modification(self):
loops = 200
self.run_one(writer, reader)
+ def test_per_type_cache_concurrent_reads(self):
+ class C:
+ pass
+
+ names = [sys.intern(f"attr_{i}") for i in range(
+ _testinternalcapi._Py_TYPECACHE_MINSIZE * 4)]
+ for name in names:
+ setattr(C, name, name)
+ # Prime the cache.
+ for name in names:
+ getattr(C, name)
+
+ lookup = _testinternalcapi.type_cache_lookup
+
+ def reader():
+ for _ in range(500):
+ for name in names:
+ hit, value, _ = lookup(C, name)
+ self.assertEqual(hit, 1, name)
+ self.assertEqual(value, name)
+
+ threading_helper.run_concurrently(reader, nthreads=NTHREADS)
+
+ def test_per_type_cache_concurrent_invalidate(self):
+ class C:
+ x = "value"
+
+ # Prime the cache.
+ C.x
+ hit, value, version = _testinternalcapi.type_cache_lookup(C, "x")
+ self.assertEqual(hit, 1)
+ self.assertIs(value, "value")
+ self.assertGreater(version, 0)
+
+ def reader():
+ for _ in range(10_000):
+ self.assertIs(C.x, "value")
+
+ def invalidator():
+ for _ in range(10_000):
+ _testinternalcapi.type_cache_invalidate(C)
+
+ workers = [invalidator] + [reader] * (NTHREADS - 1)
+ threading_helper.run_concurrently(workers)
+
def test_race_type_attr_added(self):
NROUNDS = 50
NSTOPPERS = 4
check((1,2,3), vsize('') + self.P + 3*self.P)
# type
# static type: PyTypeObject
- fmt = 'P2nPI13Pl4Pn9Pn12PI2Pc'
+ fmt = 'P2nPI13Pl4Pn9Pn12PI2PcP'
s = vsize(fmt)
check(int, s)
typeid = 'n' if support.Py_GIL_DISABLED else ''
""" Tests for the internal type cache in CPython. """
import collections.abc
import dis
+import sys
import unittest
import warnings
from test import support
self._check_specialization(to_bool_2, H(), "TO_BOOL", should_specialize=False)
+@support.cpython_only
+class PerTypeLookupCacheTests(unittest.TestCase):
+ """Tests for the per-type lookup cache."""
+
+ type_cache_lookup = staticmethod(_testinternalcapi.type_cache_lookup)
+ type_cache_invalidate = staticmethod(_testinternalcapi.type_cache_invalidate)
+
+ def _make_type(self):
+ class C:
+ x = "x-value"
+ return C
+
+ def test_lookup_miss_on_empty_cache(self):
+ # A freshly-created type has not cached any names yet; the cache
+ # should report a miss for an arbitrary name.
+ C = self._make_type()
+ hit, value, version = self.type_cache_lookup(C, "x")
+ self.assertEqual(hit, 0)
+ self.assertIsNone(value)
+ self.assertEqual(version, 0)
+
+ def test_lookup_hit_after_access(self):
+ # Reading an attribute goes through _PyType_Lookup which
+ # caches the result. Subsequent lookups for the same name
+ # should hit the cache.
+ C = self._make_type()
+ hit, value, version = self.type_cache_lookup(C, "x")
+ self.assertEqual(hit, 0)
+ attr = C.x
+ hit, value, version = self.type_cache_lookup(C, "x")
+ self.assertEqual(hit, 1)
+ self.assertIs(value, attr)
+ self.assertNotEqual(version, 0)
+ self.assertEqual(version, type_get_version(C))
+
+ def test_lookup_caches_missing_name(self):
+ # _PyType_Lookup caches negative results too: a name that is not in
+ # the MRO should still produce a cache hit with a None value.
+ C = self._make_type()
+ with self.assertRaises(AttributeError):
+ C.does_not_exist
+ hit, value, _ = self.type_cache_lookup(C, "does_not_exist")
+ self.assertEqual(hit, 1)
+ self.assertIsNone(value)
+
+ def test_lookup_on_static_type(self):
+ # The cache for static types is stored on interpreter for isolation
+ # between subinterpreters, test that cache works for them as well.
+ self.type_cache_invalidate(int)
+ name = sys.intern("bit_length")
+ self.assertEqual(self.type_cache_lookup(int, name)[0], 0)
+ attr = getattr(int, name)
+ hit, value, _ = self.type_cache_lookup(int, name)
+ self.assertEqual(hit, 1)
+ self.assertIs(value, attr)
+
+ def test_invalidate_clears_cache(self):
+ C = self._make_type()
+ C.x # populate cache
+ self.assertEqual(self.type_cache_lookup(C, "x")[0], 1)
+
+ self.type_cache_invalidate(C)
+ hit, value, _ = self.type_cache_lookup(C, "x")
+ self.assertEqual(hit, 0)
+ self.assertIsNone(value)
+
+ def test_setattr_invalidates_cache(self):
+ # Mutating a type's attributes must invalidate any cached entries
+ # for that type.
+ C = self._make_type()
+ C.x
+ self.assertEqual(self.type_cache_lookup(C, "x")[0], 1)
+
+ C.x = "new-value"
+ hit, _, _ = self.type_cache_lookup(C, "x")
+ self.assertEqual(hit, 0)
+
+ # The next access should re-populate the cache with the new value.
+ self.assertEqual(C.x, "new-value")
+ hit, value, _ = self.type_cache_lookup(C, "x")
+ self.assertEqual(hit, 1)
+ self.assertEqual(value, "new-value")
+
+ def test_setattr_on_subclass_preserves_base(self):
+ # Adding an attribute to a subclass changes the lookup result for
+ # the subclass, so its cache must be invalidated, but the base's
+ # cache for the same name stays valid.
+ class Base:
+ x = "base"
+ class Sub(Base):
+ pass
+
+ self.assertEqual(Sub.x, "base")
+ self.assertEqual(Base.x, "base")
+ self.assertEqual(self.type_cache_lookup(Sub, "x")[0], 1)
+ self.assertEqual(self.type_cache_lookup(Base, "x")[0], 1)
+
+ Sub.x = "sub"
+ # Sub's cache should be invalidated.
+ self.assertEqual(self.type_cache_lookup(Sub, "x")[0], 0)
+ # Base is untouched.
+ hit, value, _ = self.type_cache_lookup(Base, "x")
+ self.assertEqual(hit, 1)
+ self.assertEqual(value, "base")
+
+ def test_setattr_on_base_invalidates_subclass(self):
+ class Base:
+ x = "base"
+ class Sub(Base):
+ pass
+
+ Sub.x
+ self.assertEqual(self.type_cache_lookup(Sub, "x")[0], 1)
+
+ Base.x = "new-base"
+ # Modifying the base must invalidate the subclass cache too.
+ self.assertEqual(self.type_cache_lookup(Sub, "x")[0], 0)
+
+ def test_lookup_detects_stale_cache_version(self):
+ # The cache stores the type's tp_version_tag alongside its entries
+ # and re-checks it after locating a hit. If the type version moves
+ # forward without the cache being invalidated (the race window in
+ # lock-free invalidation), the consistency check must downgrade
+ # the hit to a miss.
+ C = self._make_type()
+ C.x # populate cache
+ orig_version = type_get_version(C)
+ self.assertNotEqual(orig_version, 0)
+ self.assertEqual(self.type_cache_lookup(C, "x")[0], 1)
+
+ # Bump the type version directly without touching the cache slot
+ # (PyType_Modified would also invalidate, defeating the test).
+ type_assign_specific_version_unsafe(C, orig_version + 1)
+ self.assertEqual(type_get_version(C), orig_version + 1)
+
+ hit, value, _ = self.type_cache_lookup(C, "x")
+ self.assertEqual(hit, 0)
+ self.assertIsNone(value)
+
+ def test_setattr_on_unrelated_type_preserves_cache(self):
+ # Modifying one type must not invalidate a sibling's cache.
+ class A:
+ x = "a"
+ class B:
+ x = "b"
+
+ A.x
+ B.x
+ self.assertEqual(self.type_cache_lookup(A, "x")[0], 1)
+ self.assertEqual(self.type_cache_lookup(B, "x")[0], 1)
+
+ B.x = "b2"
+ # A's cache is unaffected.
+ hit, value, _ = self.type_cache_lookup(A, "x")
+ self.assertEqual(hit, 1)
+ self.assertEqual(value, "a")
+
+
if __name__ == "__main__":
unittest.main()
Python/thread.o \
Python/traceback.o \
Python/tracemalloc.o \
+ Python/typecache.o \
Python/uniqueid.o \
Python/getopt.o \
Python/pystrcmp.o \
$(srcdir)/Include/internal/pycore_tracemalloc.h \
$(srcdir)/Include/internal/pycore_tstate.h \
$(srcdir)/Include/internal/pycore_tuple.h \
+ $(srcdir)/Include/internal/pycore_typecache.h \
$(srcdir)/Include/internal/pycore_typedefs.h \
$(srcdir)/Include/internal/pycore_typeobject.h \
$(srcdir)/Include/internal/pycore_typevarobject.h \
--- /dev/null
+The internal method cache used for types is now a per-type cache instead of a global per-interpreter one, improving performance and reducing cache misses. Patch by Kumar Aditya.
@MODULE_XXSUBTYPE_TRUE@xxsubtype xxsubtype.c
@MODULE__XXTESTFUZZ_TRUE@_xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
@MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
-@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tuple.c
+@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tuple.c _testinternalcapi/typecache.c
@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c _testcapi/weakref.c
@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c _testlimitedcapi/run.c
@MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c
if (_PyTestInternalCapi_Init_Tuple(module) < 0) {
return 1;
}
+ if (_PyTestInternalCapi_Init_TypeCache(module) < 0) {
+ return 1;
+ }
Py_ssize_t sizeof_gc_head = 0;
#ifndef Py_GIL_DISABLED
int _PyTestInternalCapi_Init_Complex(PyObject *module);
int _PyTestInternalCapi_Init_CriticalSection(PyObject *module);
int _PyTestInternalCapi_Init_Tuple(PyObject *module);
+int _PyTestInternalCapi_Init_TypeCache(PyObject *module);
#endif // Py_TESTINTERNALCAPI_PARTS_H
--- /dev/null
+// Test wrappers for the per-type lookup cache (pycore_typecache.h).
+//
+// Insertion is exercised indirectly through normal attribute access (which
+// calls _PyType_Lookup); only Lookup and Invalidate need direct wrappers.
+
+#include "parts.h"
+
+#include "pycore_critical_section.h"
+#include "pycore_pystate.h" // _PyInterpreterState_GET()
+#include "pycore_stackref.h" // PyStackRef_AsPyObjectSteal()
+#include "pycore_typecache.h" // _PyTypeCache_Lookup()
+
+
+static int
+require_type(PyObject *obj)
+{
+ if (!PyType_Check(obj)) {
+ PyErr_SetString(PyExc_TypeError, "expected a type");
+ return -1;
+ }
+ return 0;
+}
+
+static PyObject *
+intern_name(PyObject *name)
+{
+ if (!PyUnicode_CheckExact(name)) {
+ PyErr_SetString(PyExc_TypeError, "name must be a str");
+ return NULL;
+ }
+ Py_INCREF(name);
+ PyUnicode_InternInPlace(&name);
+ return name;
+}
+
+// type_cache_lookup(type, name) -> (cache_hit, value_or_None, version_tag)
+static PyObject *
+type_cache_lookup(PyObject *Py_UNUSED(self), PyObject *args)
+{
+ PyObject *type_obj, *name;
+ if (!PyArg_ParseTuple(args, "OU", &type_obj, &name)) {
+ return NULL;
+ }
+ if (require_type(type_obj) < 0) {
+ return NULL;
+ }
+ name = intern_name(name);
+ if (name == NULL) {
+ return NULL;
+ }
+ struct _PyTypeCacheLookupResult r =
+ _PyTypeCache_Lookup((PyTypeObject *)type_obj, name);
+ Py_DECREF(name);
+ PyObject *value;
+ if (PyStackRef_IsNull(r.value)) {
+ value = Py_NewRef(Py_None);
+ }
+ else {
+ value = PyStackRef_AsPyObjectSteal(r.value);
+ }
+ return Py_BuildValue("(iNk)",
+ r.cache_hit, value,
+ (unsigned long)r.version_tag);
+}
+
+static PyObject *
+type_cache_invalidate(PyObject *Py_UNUSED(self), PyObject *type_obj)
+{
+ if (require_type(type_obj) < 0) {
+ return NULL;
+ }
+ Py_BEGIN_CRITICAL_SECTION_MUTEX(&_PyInterpreterState_GET()->types.mutex);
+ _PyTypeCache_Invalidate((PyTypeObject *)type_obj);
+ Py_END_CRITICAL_SECTION();
+ Py_RETURN_NONE;
+}
+
+
+static PyMethodDef test_methods[] = {
+ {"type_cache_lookup", type_cache_lookup, METH_VARARGS},
+ {"type_cache_invalidate", type_cache_invalidate, METH_O},
+ {NULL},
+};
+
+int
+_PyTestInternalCapi_Init_TypeCache(PyObject *m)
+{
+ if (PyModule_AddFunctions(m, test_methods) < 0) {
+ return -1;
+ }
+ if (PyModule_AddIntMacro(m, _Py_TYPECACHE_MINSIZE) < 0) {
+ return -1;
+ }
+ return 0;
+}
#include "pycore_slots.h" // _PySlotIterator_Init
#include "pycore_symtable.h" // _Py_Mangle()
#include "pycore_tuple.h" // _PyTuple_FromPair
-#include "pycore_typeobject.h" // struct type_cache
+#include "pycore_typecache.h" // _PyTypeCache_Lookup()
+#include "pycore_typeobject.h" // _PyTypes_InitTypes()
#include "pycore_unicodeobject.h" // _PyUnicode_Copy
#include "pycore_unionobject.h" // _Py_union_type_or
#include "pycore_weakref.h" // _PyWeakref_GET_REF()
/* Support type attribute lookup cache */
-/* The cache can keep references to the names alive for longer than
- they normally would. This is why the maximum size is limited to
- MCACHE_MAX_ATTR_SIZE, since it might be a problem if very large
- strings are used as attribute names. */
-#define MCACHE_MAX_ATTR_SIZE 100
-#define MCACHE_HASH(version, name_hash) \
- (((unsigned int)(version) ^ (unsigned int)(name_hash)) \
- & ((1 << MCACHE_SIZE_EXP) - 1))
-
-#define MCACHE_HASH_METHOD(type, name) \
- MCACHE_HASH(FT_ATOMIC_LOAD_UINT_RELAXED((type)->tp_version_tag), \
- ((Py_ssize_t)(name)) >> 3)
-#define MCACHE_CACHEABLE_NAME(name) \
- (PyUnicode_CheckExact(name) && \
- (PyUnicode_GET_LENGTH(name) <= MCACHE_MAX_ATTR_SIZE))
+#define MCACHE_CACHEABLE_NAME(name) (PyUnicode_CheckExact(name) && PyUnicode_CHECK_INTERNED(name))
#define NEXT_VERSION_TAG(interp) \
(interp)->types.next_version_tag
}
-static struct type_cache*
-get_type_cache(void)
-{
- PyInterpreterState *interp = _PyInterpreterState_GET();
- return &interp->types.type_cache;
-}
-
-
-static void
-type_cache_clear(struct type_cache *cache, PyObject *value)
-{
- for (Py_ssize_t i = 0; i < (1 << MCACHE_SIZE_EXP); i++) {
- struct type_cache_entry *entry = &cache->hashtable[i];
-#ifdef Py_GIL_DISABLED
- _PySeqLock_LockWrite(&entry->sequence);
-#endif
- entry->version = 0;
- Py_XSETREF(entry->name, _Py_XNewRef(value));
- entry->value = NULL;
-#ifdef Py_GIL_DISABLED
- _PySeqLock_UnlockWrite(&entry->sequence);
-#endif
- }
-}
-
-
-void
-_PyType_InitCache(PyInterpreterState *interp)
-{
- struct type_cache *cache = &interp->types.type_cache;
- for (Py_ssize_t i = 0; i < (1 << MCACHE_SIZE_EXP); i++) {
- struct type_cache_entry *entry = &cache->hashtable[i];
- assert(entry->name == NULL);
-
- entry->version = 0;
- // Set to None so _PyType_LookupRef() can use Py_SETREF(),
- // rather than using slower Py_XSETREF().
- entry->name = Py_None;
- entry->value = NULL;
- }
-}
-
-
-static unsigned int
-_PyType_ClearCache(PyInterpreterState *interp)
-{
- struct type_cache *cache = &interp->types.type_cache;
- // Set to None, rather than NULL, so _PyType_LookupRef() can
- // use Py_SETREF() rather than using slower Py_XSETREF().
- type_cache_clear(cache, Py_None);
-
- return NEXT_VERSION_TAG(interp) - 1;
-}
-
-
unsigned int
PyType_ClearCache(void)
{
PyInterpreterState *interp = _PyInterpreterState_GET();
- return _PyType_ClearCache(interp);
+ return NEXT_VERSION_TAG(interp) - 1;
}
void
_PyTypes_Fini(PyInterpreterState *interp)
{
- struct type_cache *cache = &interp->types.type_cache;
- type_cache_clear(cache, NULL);
-
// All the managed static types should have been finalized already.
assert(interp->types.for_extensions.num_initialized == 0);
for (size_t i = 0; i < _Py_MAX_MANAGED_STATIC_EXT_TYPES; i++) {
}
set_version_unlocked(type, 0); /* 0 is not a valid version tag */
+ _PyTypeCache_Invalidate(type);
if (PyType_HasFeature(type, Py_TPFLAGS_HEAPTYPE)) {
// This field *must* be invalidated if the type is modified (see the
// comment on struct _specialization_cache):
clear:
assert(!(type->tp_flags & _Py_TPFLAGS_STATIC_BUILTIN));
set_version_unlocked(type, 0); /* 0 is not a valid version tag */
+ _PyTypeCache_Invalidate(type);
type->tp_versions_used = _Py_ATTR_CACHE_UNUSED;
if (PyType_HasFeature(type, Py_TPFLAGS_HEAPTYPE)) {
// This field *must* be invalidated if the type is modified (see the
return 0;
}
-static PyObject *
-update_cache(struct type_cache_entry *entry, PyObject *name, unsigned int version_tag, PyObject *value)
-{
- _Py_atomic_store_ptr_relaxed(&entry->value, value); /* borrowed */
- assert(PyUnstable_Unicode_GET_CACHED_HASH(name) != -1);
- OBJECT_STAT_INC_COND(type_cache_collisions, entry->name != Py_None && entry->name != name);
- // We're releasing this under the lock for simplicity sake because it's always a
- // exact unicode object or Py_None so it's safe to do so.
- PyObject *old_name = entry->name;
- _Py_atomic_store_ptr_relaxed(&entry->name, Py_NewRef(name));
- // We must write the version last to avoid _Py_TryXGetStackRef()
- // operating on an invalid (already deallocated) value inside
- // _PyType_LookupRefAndVersion(). If we write the version first then a
- // reader could pass the "entry_version == type_version" check but could
- // be using the old entry value.
- _Py_atomic_store_uint32_release(&entry->version, version_tag);
- return old_name;
-}
-
-#if Py_GIL_DISABLED
-
-static void
-update_cache_gil_disabled(struct type_cache_entry *entry, PyObject *name,
- unsigned int version_tag, PyObject *value)
-{
- _PySeqLock_LockWrite(&entry->sequence);
-
- // update the entry
- if (entry->name == name &&
- entry->value == value &&
- entry->version == version_tag) {
- // We raced with another update, bail and restore previous sequence.
- _PySeqLock_AbandonWrite(&entry->sequence);
- return;
- }
-
- PyObject *old_value = update_cache(entry, name, version_tag, value);
-
- // Then update sequence to the next valid value
- _PySeqLock_UnlockWrite(&entry->sequence);
-
- Py_DECREF(old_value);
-}
-
-#endif
-
-void
-_PyTypes_AfterFork(void)
-{
-#ifdef Py_GIL_DISABLED
- struct type_cache *cache = get_type_cache();
- for (Py_ssize_t i = 0; i < (1 << MCACHE_SIZE_EXP); i++) {
- struct type_cache_entry *entry = &cache->hashtable[i];
- if (_PySeqLock_AfterFork(&entry->sequence)) {
- // Entry was in the process of updating while forking, clear it...
- entry->value = NULL;
- Py_SETREF(entry->name, Py_None);
- entry->version = 0;
- }
- }
-#endif
-}
-
/* Internal API to look for a name through the MRO.
This returns a strong reference, and doesn't set an exception!
If nonzero, version is set to the value of type->tp_version at the time of
unsigned int
_PyType_LookupStackRefAndVersion(PyTypeObject *type, PyObject *name, _PyStackRef *out)
{
- unsigned int h = MCACHE_HASH_METHOD(type, name);
- struct type_cache *cache = get_type_cache();
- struct type_cache_entry *entry = &cache->hashtable[h];
-#ifdef Py_GIL_DISABLED
- // synchronize-with other writing threads by doing an acquire load on the sequence
- while (1) {
- uint32_t sequence = _PySeqLock_BeginRead(&entry->sequence);
- uint32_t entry_version = _Py_atomic_load_uint32_acquire(&entry->version);
- uint32_t type_version = _Py_atomic_load_uint32_acquire(&type->tp_version_tag);
- if (entry_version == type_version &&
- _Py_atomic_load_ptr_relaxed(&entry->name) == name) {
+ int cacheable = MCACHE_CACHEABLE_NAME(name);
+ if (cacheable) {
+ struct _PyTypeCacheLookupResult r = _PyTypeCache_Lookup(type, name);
+ if (r.cache_hit) {
OBJECT_STAT_INC_COND(type_cache_hits, !is_dunder_name(name));
OBJECT_STAT_INC_COND(type_cache_dunder_hits, is_dunder_name(name));
- if (_Py_TryXGetStackRef(&entry->value, out)) {
- // If the sequence is still valid then we're done
- if (_PySeqLock_EndRead(&entry->sequence, sequence)) {
- return entry_version;
- }
- PyStackRef_XCLOSE(*out);
- }
- else {
- // If we can't incref the object we need to fallback to locking
- break;
- }
- }
- else {
- // cache miss
- break;
+ *out = r.value;
+ return r.version_tag;
}
}
-#else
- if (entry->version == type->tp_version_tag && entry->name == name) {
- assert(type->tp_version_tag);
- OBJECT_STAT_INC_COND(type_cache_hits, !is_dunder_name(name));
- OBJECT_STAT_INC_COND(type_cache_dunder_hits, is_dunder_name(name));
- *out = entry->value ? PyStackRef_FromPyObjectNew(entry->value) : PyStackRef_NULL;
- return entry->version;
- }
-#endif
OBJECT_STAT_INC_COND(type_cache_misses, !is_dunder_name(name));
OBJECT_STAT_INC_COND(type_cache_dunder_misses, is_dunder_name(name));
PyInterpreterState *interp = _PyInterpreterState_GET();
unsigned int version_tag = FT_ATOMIC_LOAD_UINT(type->tp_version_tag);
- if (should_assign_version_tag(type, name, version_tag)) {
+ if (cacheable &&
+ (version_tag != 0 || should_assign_version_tag(type, name, version_tag)))
+ {
BEGIN_TYPE_LOCK();
- assign_version_tag(interp, type);
version_tag = type->tp_version_tag;
+ if (version_tag == 0) {
+ assign_version_tag(interp, type);
+ version_tag = type->tp_version_tag;
+ }
res = find_name_in_mro(type, name, out);
+ // find_name_in_mro can release the type lock and another thread can
+ // modify the type, so we need to check version tag again before caching the result.
+ if (res >= 0 && version_tag != 0 && version_tag == type->tp_version_tag) {
+ _PyTypeCache_Insert(type, name, PyStackRef_AsPyObjectBorrow(*out));
+ }
END_TYPE_LOCK();
}
else {
+ version_tag = 0;
res = find_name_in_mro(type, name, out);
}
return 0;
}
- if (version_tag == 0 || !MCACHE_CACHEABLE_NAME(name)) {
- return 0;
- }
-
- PyObject *res_obj = PyStackRef_AsPyObjectBorrow(*out);
-#if Py_GIL_DISABLED
- update_cache_gil_disabled(entry, name, version_tag, res_obj);
-#else
- PyObject *old_value = update_cache(entry, name, version_tag, res_obj);
- Py_DECREF(old_value);
-#endif
return version_tag;
}
done:
Py_DECREF(name);
Py_XDECREF(descr);
- Py_XDECREF(old_value);
+ // delay decref of the old value as lock-free type cache readers may access it
+ if (old_value != NULL && !_Py_IsImmortal(old_value)) {
+ _PyObject_XDecRefDelayed(old_value);
+ }
return res;
}
if (final) {
Py_CLEAR(type->tp_cache);
}
+ _PyTypeCache_Invalidate(type);
clear_tp_dict(type);
clear_tp_bases(type, final);
clear_tp_mro(type, final);
Py_XDECREF(type->tp_mro);
Py_XDECREF(type->tp_cache);
clear_tp_subclasses(type);
+ _PyTypeCache_Invalidate(type);
/* A type's tp_doc is heap allocated, unlike the tp_doc slots
* of most other objects. It's okay to cast it to char *.
goto error;
}
+ _PyTypeCache_InitType(type);
+
#ifdef Py_TRACE_REFS
/* PyType_Ready is the closest thing we have to a choke point
* for type objects, so is the best place I can think of to try
<ClCompile Include="..\Python\thread.c" />
<ClCompile Include="..\Python\traceback.c" />
<ClCompile Include="..\Python\tracemalloc.c" />
+ <ClCompile Include="..\Python\typecache.c" />
<ClCompile Include="..\Python\uniqueid.c" />
</ItemGroup>
<ItemGroup>
<ClCompile Include="..\Python\tracemalloc.c">
<Filter>Source Files</Filter>
</ClCompile>
+ <ClCompile Include="..\Python\typecache.c">
+ <Filter>Source Files</Filter>
+ </ClCompile>
<ClCompile Include="..\Python\uniqueid.c">
<Filter>Source Files</Filter>
</ClCompile>
<ClCompile Include="..\Modules\_testinternalcapi\complex.c" />
<ClCompile Include="..\Modules\_testinternalcapi\interpreter.c" />
<ClCompile Include="..\Modules\_testinternalcapi\tuple.c" />
+ <ClCompile Include="..\Modules\_testinternalcapi\typecache.c" />
</ItemGroup>
<ItemGroup>
<ResourceCompile Include="..\PC\python_nt.rc" />
<ClCompile Include="..\Modules\_testinternalcapi\tuple.c">
<Filter>Source Files</Filter>
</ClCompile>
+ <ClCompile Include="..\Modules\_testinternalcapi\typecache.c">
+ <Filter>Source Files</Filter>
+ </ClCompile>
</ItemGroup>
<ItemGroup>
<ResourceCompile Include="..\PC\python_nt.rc">
<ClInclude Include="..\Include\internal\pycore_tracemalloc.h" />
<ClInclude Include="..\Include\internal\pycore_tstate.h" />
<ClInclude Include="..\Include\internal\pycore_tuple.h" />
+ <ClInclude Include="..\Include\internal\pycore_typecache.h" />
<ClInclude Include="..\Include\internal\pycore_typedefs.h" />
<ClInclude Include="..\Include\internal\pycore_typeobject.h" />
<ClInclude Include="..\Include\internal\pycore_typevarobject.h" />
<ClCompile Include="..\Python\thread.c" />
<ClCompile Include="..\Python\traceback.c" />
<ClCompile Include="..\Python\tracemalloc.c" />
+ <ClCompile Include="..\Python\typecache.c" />
<ClCompile Include="..\Python\uniqueid.c" />
</ItemGroup>
<ItemGroup Condition="$(IncludeExternals)">
<ClInclude Include="..\Include\internal\pycore_tuple.h">
<Filter>Include\internal</Filter>
</ClInclude>
+ <ClInclude Include="..\Include\internal\pycore_typecache.h">
+ <Filter>Include\internal</Filter>
+ </ClInclude>
<ClInclude Include="..\Include\internal\pycore_typedefs.h">
<Filter>Include\internal</Filter>
</ClInclude>
<ClCompile Include="..\Python\tracemalloc.c">
<Filter>Python</Filter>
</ClCompile>
+ <ClCompile Include="..\Python\typecache.c">
+ <Filter>Python</Filter>
+ </ClCompile>
<ClCompile Include="..\Python\uniqueid.c">
<Filter>Python</Filter>
</ClCompile>
#include "pycore_freelist.h" // _PyObject_ClearFreeLists()
#include "pycore_initconfig.h" // _PyStatus_OK()
#include "pycore_interpframe.h" // _PyThreadState_HasStackSpace()
-#include "pycore_object.h" // _PyType_InitCache(), _Py_ClearImmortal()
+#include "pycore_object.h" // _Py_ClearImmortal()
#include "pycore_obmalloc.h" // _PyMem_obmalloc_state_on_heap()
#include "pycore_opcode_utils.h" // NUM_COMMON_CONSTANTS
#include "pycore_optimizer.h" // JIT_CLEANUP_THRESHOLD
}
#endif
- _PyTypes_AfterFork();
-
_PyThread_AfterFork(&runtime->threads);
return _PyStatus_OK();
_PyEval_InitState(interp);
_PyGC_InitState(&interp->gc);
PyConfig_InitPythonConfig(&interp->config);
- _PyType_InitCache(interp);
#ifdef Py_GIL_DISABLED
_Py_brc_init_state(interp);
#endif
fprintf(out, "Object materialize dict (str subclass): %" PRIu64 "\n", stats->dict_materialized_str_subclass);
fprintf(out, "Object method cache hits: %" PRIu64 "\n", stats->type_cache_hits);
fprintf(out, "Object method cache misses: %" PRIu64 "\n", stats->type_cache_misses);
- fprintf(out, "Object method cache collisions: %" PRIu64 "\n", stats->type_cache_collisions);
+ fprintf(out, "Object method cache too big: %" PRIu64 "\n", stats->type_cache_too_big);
fprintf(out, "Object method cache dunder hits: %" PRIu64 "\n", stats->type_cache_dunder_hits);
fprintf(out, "Object method cache dunder misses: %" PRIu64 "\n", stats->type_cache_dunder_misses);
+ fprintf(out, "Object method cache invalidations: %" PRIu64 "\n", stats->type_cache_invalidations);
+ fprintf(out, "Object method cache resizes: %" PRIu64 "\n", stats->type_cache_resizes);
}
static void
dest->type_cache_misses += src->type_cache_misses;
dest->type_cache_dunder_hits += src->type_cache_dunder_hits;
dest->type_cache_dunder_misses += src->type_cache_dunder_misses;
- dest->type_cache_collisions += src->type_cache_collisions;
+ dest->type_cache_too_big += src->type_cache_too_big;
+ dest->type_cache_invalidations += src->type_cache_invalidations;
+ dest->type_cache_resizes += src->type_cache_resizes;
dest->object_visits += src->object_visits;
}
--- /dev/null
+// Per-type method cache implementation
+
+// The cache is used for method and attribute lookups on type objects.
+// The stored names are always interned strings, and the
+// stored values are borrowed references to the corresponding method or attribute object.
+// For static types, the cache is stored on the per-interpreter managed_static_type_state,
+// and for heap types the cache is stored in the `PyTypeObject._tp_cache` field.
+
+#include "Python.h"
+#include "pycore_typecache.h"
+#include "pycore_interp.h" // PyInterpreterState
+#include "pycore_pymem.h"
+#include "pycore_pystate.h" // _PyInterpreterState_GET()
+#include "pycore_pyatomic_ft_wrappers.h"
+#include "pycore_typeobject.h" // _PyStaticType_GetState()
+#include "pycore_stats.h" // OBJECT_STAT_INC
+
+
+// The empty cache is statically allocated and shared across all the types,
+// when a type is modified, the cache of type is set to the empty cache
+// and when a cache entry is inserted to the empty cache, a new cache is
+// allocated for the type and the entry is inserted to the new cache.
+static struct type_cache empty_cache = {
+ .mask = _Py_TYPECACHE_MINSIZE - 1,
+ .version_tag = 0,
+ .available = 0,
+ .used = 0,
+};
+
+static inline uint32_t
+cache_size(struct type_cache *cache)
+{
+ return cache->mask + 1;
+}
+
+static inline size_t
+cache_nbytes(struct type_cache *cache)
+{
+ return offsetof(struct type_cache, hashtable)
+ + (size_t)cache_size(cache) * sizeof(struct type_cache_entry);
+}
+
+static struct type_cache *
+cache_allocate(uint32_t size)
+{
+ // size must be a power of two
+ assert((size & (size - 1)) == 0);
+ size_t nbytes = offsetof(struct type_cache, hashtable)
+ + (size_t)size * sizeof(struct type_cache_entry);
+ struct type_cache *cache = PyMem_Calloc(1, nbytes);
+ if (cache == NULL) {
+ return NULL;
+ }
+ cache->mask = size - 1;
+ // load factor of 0.75
+ cache->available = size - (size >> 2);
+ cache->used = 0;
+ return cache;
+}
+
+static void
+cache_free_delayed(struct type_cache *cache)
+{
+ if (cache == NULL || cache == &empty_cache) {
+ return;
+ }
+#ifndef Py_GIL_DISABLED
+ // On gil-enabled builds, the cache owns strong references to the interned strings,
+ // so we need to decref them before freeing the cache memory.
+ for (uint32_t i = 0; i < cache_size(cache); i++) {
+ if (cache->hashtable[i].name != NULL) {
+ Py_DECREF(cache->hashtable[i].name);
+ }
+ }
+#endif
+ // Delay the freeing of old cache for concurrent lock-free readers
+ _PyMem_FreeDelayed(cache, cache_nbytes(cache));
+}
+
+
+static inline void **
+cache_slot(PyTypeObject *type)
+{
+ if (type->tp_flags & _Py_TPFLAGS_STATIC_BUILTIN) {
+ PyInterpreterState *interp = _PyInterpreterState_GET();
+ managed_static_type_state *state = _PyStaticType_GetState(interp, type);
+ assert(state != NULL);
+ return &state->_tp_cache;
+ }
+ return &type->_tp_cache;
+}
+
+static inline struct type_cache *
+cache_get(PyTypeObject *type)
+{
+ return (struct type_cache *)FT_ATOMIC_LOAD_PTR_ACQUIRE(*cache_slot(type));
+}
+
+static inline void
+cache_set(PyTypeObject *type, struct type_cache *cache)
+{
+ FT_ATOMIC_STORE_PTR_RELEASE(*cache_slot(type), cache);
+}
+
+void
+_PyTypeCache_InitType(PyTypeObject *type)
+{
+ *cache_slot(type) = &empty_cache;
+}
+
+static inline void
+cache_insert(struct type_cache *cache, PyObject *name,
+ PyObject *value)
+{
+ Py_hash_t hash = PyUnstable_Unicode_GET_CACHED_HASH(name);
+ assert(hash != -1);
+ uint32_t index = hash & cache->mask;
+ for (;;) {
+ if (cache->hashtable[index].name == NULL) {
+#ifndef Py_GIL_DISABLED
+ // On free-threading, all interned strings are immortal.
+ Py_INCREF(name);
+#endif
+ cache->hashtable[index].value = value;
+ FT_ATOMIC_STORE_PTR_RELEASE(cache->hashtable[index].name, name);
+ cache->used++;
+ cache->available--;
+ return;
+ }
+ else if (cache->hashtable[index].name == name) {
+ /* someone else added the entry before us. */
+ return;
+ }
+ index = (index + 1) & cache->mask;
+ }
+}
+
+static inline int
+cache_resize(PyTypeObject *type, struct type_cache *cache)
+{
+ uint32_t old_size = cache_size(cache);
+ uint32_t new_size;
+ if (cache->used == 0) {
+ // the cache is the empty cache, we need to allocate a new cache with the minimum size
+ new_size = _Py_TYPECACHE_MINSIZE;
+ }
+ else {
+ // double the cache size when resizing
+ new_size = old_size * 2;
+ }
+ if (new_size > _Py_TYPECACHE_MAXSIZE) {
+ // The new size is too big, don't resize and just return.
+ OBJECT_STAT_INC(type_cache_too_big);
+ return -1;
+ }
+ struct type_cache *new_cache = cache_allocate(new_size);
+ if (new_cache == NULL) {
+ return -1;
+ }
+ OBJECT_STAT_INC(type_cache_resizes);
+ for (uint32_t i = 0; i < old_size; i++) {
+ if (cache->hashtable[i].name != NULL) {
+ cache_insert(new_cache, cache->hashtable[i].name, cache->hashtable[i].value);
+ }
+ }
+ new_cache->version_tag = type->tp_version_tag;
+ cache_set(type, new_cache);
+ cache_free_delayed(cache);
+ return 0;
+}
+
+// Insert a new entry to the type cache.
+// The TYPE_LOCK should be held while calling this function.
+void
+_PyTypeCache_Insert(PyTypeObject *type, PyObject *name, PyObject *value)
+{
+ struct type_cache *cache = cache_get(type);
+ // If the cache is full, resize it before inserting the new entry.
+ // this also handles the case of empty cache where available is 0 but there are no entries.
+ if (cache->available == 0) {
+ if (cache_resize(type, cache) == -1) {
+ // out of memory, don't cache the value
+ return;
+ }
+ cache = cache_get(type);
+ assert(cache->available > 0);
+ }
+ assert(cache->version_tag == type->tp_version_tag);
+ cache_insert(cache, name, value);
+}
+
+
+// Lookup the given name in the type cache.
+// The cache is lock-free so it is possible that cache becomes stale during the lookup,
+// to prevent returning stale cache entry, the cache version is compared with the type version tag.
+struct _PyTypeCacheLookupResult
+_PyTypeCache_Lookup(PyTypeObject *type, PyObject *name)
+{
+ assert(PyUnicode_CheckExact(name) && PyUnicode_CHECK_INTERNED(name));
+ struct _PyTypeCacheLookupResult miss = {PyStackRef_NULL, 0, 0};
+ struct type_cache *cache = cache_get(type);
+ if (cache == NULL) {
+ return miss;
+ }
+ Py_hash_t hash = PyUnstable_Unicode_GET_CACHED_HASH(name);
+ assert(hash != -1);
+ uint32_t index = hash & cache->mask;
+ _PyStackRef out_ref;
+ for (;;) {
+ PyObject *entry_name = FT_ATOMIC_LOAD_PTR_ACQUIRE(cache->hashtable[index].name);
+ if (entry_name == name) {
+#ifdef Py_GIL_DISABLED
+ if (!_Py_TryXGetStackRef(&cache->hashtable[index].value, &out_ref)) {
+ return miss;
+ }
+#else
+ PyObject *v = cache->hashtable[index].value;
+ out_ref = v ? PyStackRef_FromPyObjectNew(v) : PyStackRef_NULL;
+#endif
+ break;
+ }
+ else if (entry_name == NULL) {
+ return miss;
+ }
+ index = (index + 1) & cache->mask;
+ }
+ // Check the cache version against the type version tag to maintain
+ // consistency with find_name_in_mro and prevent stale cache reads
+ if (cache->version_tag != FT_ATOMIC_LOAD_UINT_RELAXED(type->tp_version_tag)) {
+ PyStackRef_XCLOSE(out_ref);
+ return miss;
+ }
+ return (struct _PyTypeCacheLookupResult){out_ref, 1, cache->version_tag};
+}
+
+// Invalidate the type cache of the type.
+// The cache is set to the empty cache and the old cache is freed with QSBR.
+// The TYPE_LOCK should be held while calling this function.
+void
+_PyTypeCache_Invalidate(PyTypeObject *type)
+{
+ OBJECT_STAT_INC(type_cache_invalidations);
+ struct type_cache *cache = cache_get(type);
+ cache_set(type, &empty_cache);
+ cache_free_delayed(cache);
+}
## thread-safe hashtable (internal locks)
Python/parking_lot.c - buckets -
+## shared empty sentinel for the per-type method cache
+Python/typecache.c - empty_cache -
+
## data needed for introspecting asyncio state from debuggers and profilers
Modules/_asynciomodule.c - _Py_AsyncioDebug -
MyEnum.Y
MyEnum.Z
+_MCACHE_NUM_TYPES = 1 << 14
+_MCACHE_PAIRS = [
+ (type(f"C{i}", (), {f"m{i}": i % 256})(), sys.intern(f"m{i}"))
+ for i in range(_MCACHE_NUM_TYPES)
+]
+
+@register_benchmark
+def type_lookup():
+ pairs = _MCACHE_PAIRS
+ for _ in range(WORK_SCALE // 10):
+ for inst, name in pairs:
+ getattr(inst, name)
+
def bench_one_thread(func):
t0 = time.perf_counter_ns()
projects / thirdparty / Python / cpython.git / commitdiff
