From 41010184880151d6ae02a226dbacc796e5c90d11 Mon Sep 17 00:00:00 2001 From: Victor Stinner Date: Sat, 26 Dec 2020 01:45:43 +0100 Subject: 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. --- Include/internal/pycore_interp.h | 22 +++ Include/internal/pycore_object.h | 3 + Include/internal/pycore_pylifecycle.h | 2 +- .../2020-12-25-23-30-58.bpo-42745.XsFoHS.rst | 1 + Objects/typeobject.c | 178 ++++++++++++--------- Python/pylifecycle.c | 2 +- Python/pystate.c | 2 + 7 files changed, 128 insertions(+), 82 deletions(-) create mode 100644 Misc/NEWS.d/next/Core and Builtins/2020-12-25-23-30-58.bpo-42745.XsFoHS.rst 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); diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-12-25-23-30-58.bpo-42745.XsFoHS.rst b/Misc/NEWS.d/next/Core and Builtins/2020-12-25-23-30-58.bpo-42745.XsFoHS.rst new file mode 100644 index 0000000..fb7de9c --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2020-12-25-23-30-58.bpo-42745.XsFoHS.rst @@ -0,0 +1 @@ +Make the type attribute lookup cache per-interpreter. Patch by Victor Stinner. diff --git a/Objects/typeobject.c b/Objects/typeobject.c index 83bc877..661ccb7 100644 --- a/Objects/typeobject.c +++ b/Objects/typeobject.c @@ -20,20 +20,13 @@ class object "PyObject *" "&PyBaseObject_Type" #include "clinic/typeobject.c.h" -/* bpo-40521: Type method cache is shared by all subinterpreters */ -#ifndef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS -# define MCACHE -#endif - -#ifdef MCACHE -/* Support type attribute cache */ +/* 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_SIZE_EXP 12 #define MCACHE_HASH(version, name_hash) \ (((unsigned int)(version) ^ (unsigned int)(name_hash)) \ & ((1 << MCACHE_SIZE_EXP) - 1)) @@ -44,30 +37,16 @@ class object "PyObject *" "&PyBaseObject_Type" #define MCACHE_CACHEABLE_NAME(name) \ PyUnicode_CheckExact(name) && \ PyUnicode_IS_READY(name) && \ - PyUnicode_GET_LENGTH(name) <= MCACHE_MAX_ATTR_SIZE - -struct method_cache_entry { - unsigned int version; - PyObject *name; /* reference to exactly a str or None */ - PyObject *value; /* borrowed */ -}; + (PyUnicode_GET_LENGTH(name) <= MCACHE_MAX_ATTR_SIZE) -static struct method_cache_entry method_cache[1 << MCACHE_SIZE_EXP]; +// Used to set PyTypeObject.tp_version_tag static unsigned int next_version_tag = 0; -#endif typedef struct PySlot_Offset { short subslot_offset; short slot_offset; } PySlot_Offset; -#define MCACHE_STATS 0 - -#if MCACHE_STATS -static size_t method_cache_hits = 0; -static size_t method_cache_misses = 0; -static size_t method_cache_collisions = 0; -#endif /* bpo-40521: Interned strings are shared by all subinterpreters */ #ifndef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS @@ -229,46 +208,93 @@ _PyType_GetTextSignatureFromInternalDoc(const char *name, const char *internal_d return PyUnicode_FromStringAndSize(start, end - start); } -unsigned int -PyType_ClearCache(void) + +static struct type_cache* +get_type_cache(void) { -#ifdef MCACHE - Py_ssize_t i; - unsigned int cur_version_tag = next_version_tag - 1; + PyInterpreterState *interp = _PyInterpreterState_GET(); + return &interp->type_cache; +} + +static void +type_cache_clear(struct type_cache *cache, int use_none) +{ + for (Py_ssize_t i = 0; i < (1 << MCACHE_SIZE_EXP); i++) { + struct type_cache_entry *entry = &cache->hashtable[i]; + entry->version = 0; + if (use_none) { + // Set to None so _PyType_Lookup() can use Py_SETREF(), + // rather than using slower Py_XSETREF(). + Py_XSETREF(entry->name, Py_NewRef(Py_None)); + } + else { + Py_CLEAR(entry->name); + } + entry->value = NULL; + } + + // Mark all version tags as invalid + PyType_Modified(&PyBaseObject_Type); +} + + +void +_PyType_InitCache(PyInterpreterState *interp) +{ + struct type_cache *cache = &interp->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_Lookup() can use Py_SETREF(), + // rather than using slower Py_XSETREF(). + entry->name = Py_NewRef(Py_None); + entry->value = NULL; + } +} + + +static unsigned int +_PyType_ClearCache(struct type_cache *cache) +{ #if MCACHE_STATS - size_t total = method_cache_hits + method_cache_collisions + method_cache_misses; + size_t total = cache->hits + cache->collisions + cache->misses; fprintf(stderr, "-- Method cache hits = %zd (%d%%)\n", - method_cache_hits, (int) (100.0 * method_cache_hits / total)); + cache->hits, (int) (100.0 * cache->hits / total)); fprintf(stderr, "-- Method cache true misses = %zd (%d%%)\n", - method_cache_misses, (int) (100.0 * method_cache_misses / total)); + cache->misses, (int) (100.0 * cache->misses / total)); fprintf(stderr, "-- Method cache collisions = %zd (%d%%)\n", - method_cache_collisions, (int) (100.0 * method_cache_collisions / total)); + cache->collisions, (int) (100.0 * cache->collisions / total)); fprintf(stderr, "-- Method cache size = %zd KiB\n", - sizeof(method_cache) / 1024); + sizeof(cache->hashtable) / 1024); #endif - for (i = 0; i < (1 << MCACHE_SIZE_EXP); i++) { - method_cache[i].version = 0; - Py_CLEAR(method_cache[i].name); - method_cache[i].value = NULL; - } + unsigned int cur_version_tag = next_version_tag - 1; next_version_tag = 0; - /* mark all version tags as invalid */ - PyType_Modified(&PyBaseObject_Type); + type_cache_clear(cache, 0); + return cur_version_tag; -#else - return 0; -#endif } + +unsigned int +PyType_ClearCache(void) +{ + struct type_cache *cache = get_type_cache(); + return _PyType_ClearCache(cache); +} + + void -_PyType_Fini(void) +_PyType_Fini(PyThreadState *tstate) { - PyType_ClearCache(); + _PyType_ClearCache(&tstate->interp->type_cache); clear_slotdefs(); } + void PyType_Modified(PyTypeObject *type) { @@ -370,9 +396,8 @@ type_mro_modified(PyTypeObject *type, PyObject *bases) { Py_TPFLAGS_VALID_VERSION_TAG); } -#ifdef MCACHE static int -assign_version_tag(PyTypeObject *type) +assign_version_tag(struct type_cache *cache, PyTypeObject *type) { /* Ensure that the tp_version_tag is valid and set Py_TPFLAGS_VALID_VERSION_TAG. To respect the invariant, this @@ -393,31 +418,22 @@ assign_version_tag(PyTypeObject *type) /* for stress-testing: next_version_tag &= 0xFF; */ if (type->tp_version_tag == 0) { - /* wrap-around or just starting Python - clear the whole - cache by filling names with references to Py_None. - Values are also set to NULL for added protection, as they - are borrowed reference */ - for (i = 0; i < (1 << MCACHE_SIZE_EXP); i++) { - method_cache[i].value = NULL; - Py_INCREF(Py_None); - Py_XSETREF(method_cache[i].name, Py_None); - } - /* mark all version tags as invalid */ - PyType_Modified(&PyBaseObject_Type); + // Wrap-around or just starting Python - clear the whole cache + type_cache_clear(cache, 1); return 1; } + bases = type->tp_bases; n = PyTuple_GET_SIZE(bases); for (i = 0; i < n; i++) { PyObject *b = PyTuple_GET_ITEM(bases, i); assert(PyType_Check(b)); - if (!assign_version_tag((PyTypeObject *)b)) + if (!assign_version_tag(cache, (PyTypeObject *)b)) return 0; } type->tp_flags |= Py_TPFLAGS_VALID_VERSION_TAG; return 1; } -#endif static PyMemberDef type_members[] = { @@ -3316,20 +3332,19 @@ _PyType_Lookup(PyTypeObject *type, PyObject *name) PyObject *res; int error; -#ifdef MCACHE if (MCACHE_CACHEABLE_NAME(name) && _PyType_HasFeature(type, Py_TPFLAGS_VALID_VERSION_TAG)) { /* fast path */ unsigned int h = MCACHE_HASH_METHOD(type, name); - if (method_cache[h].version == type->tp_version_tag && - method_cache[h].name == name) { + struct type_cache *cache = get_type_cache(); + struct type_cache_entry *entry = &cache->hashtable[h]; + if (entry->version == type->tp_version_tag && entry->name == name) { #if MCACHE_STATS - method_cache_hits++; + cache->hits++; #endif - return method_cache[h].value; + return entry->value; } } -#endif /* We may end up clearing live exceptions below, so make sure it's ours. */ assert(!PyErr_Occurred()); @@ -3351,22 +3366,25 @@ _PyType_Lookup(PyTypeObject *type, PyObject *name) return NULL; } -#ifdef MCACHE - if (MCACHE_CACHEABLE_NAME(name) && assign_version_tag(type)) { - unsigned int h = MCACHE_HASH_METHOD(type, name); - method_cache[h].version = type->tp_version_tag; - method_cache[h].value = res; /* borrowed */ - Py_INCREF(name); - assert(((PyASCIIObject *)(name))->hash != -1); + if (MCACHE_CACHEABLE_NAME(name)) { + struct type_cache *cache = get_type_cache(); + if (assign_version_tag(cache, type)) { + unsigned int h = MCACHE_HASH_METHOD(type, name); + struct type_cache_entry *entry = &cache->hashtable[h]; + entry->version = type->tp_version_tag; + entry->value = res; /* borrowed */ + assert(((PyASCIIObject *)(name))->hash != -1); #if MCACHE_STATS - if (method_cache[h].name != Py_None && method_cache[h].name != name) - method_cache_collisions++; - else - method_cache_misses++; + if (entry->name != Py_None && entry->name != name) { + cache->collisions++; + } + else { + cache->misses++; + } #endif - Py_SETREF(method_cache[h].name, name); + Py_SETREF(entry->name, Py_NewRef(name)); + } } -#endif return res; } diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c index 8d744c7..c3c1aa2 100644 --- a/Python/pylifecycle.c +++ b/Python/pylifecycle.c @@ -1750,7 +1750,7 @@ Py_FinalizeEx(void) _PyImport_Fini(); /* Cleanup typeobject.c's internal caches. */ - _PyType_Fini(); + _PyType_Fini(tstate); /* unload faulthandler module */ _PyFaulthandler_Fini(); diff --git a/Python/pystate.c b/Python/pystate.c index 231144b..c791b23 100644 --- a/Python/pystate.c +++ b/Python/pystate.c @@ -4,6 +4,7 @@ #include "Python.h" #include "pycore_ceval.h" #include "pycore_initconfig.h" +#include "pycore_object.h" // _PyType_InitCache() #include "pycore_pyerrors.h" #include "pycore_pylifecycle.h" #include "pycore_pymem.h" // _PyMem_SetDefaultAllocator() @@ -223,6 +224,7 @@ PyInterpreterState_New(void) _PyGC_InitState(&interp->gc); PyConfig_InitPythonConfig(&interp->config); + _PyType_InitCache(interp); interp->eval_frame = _PyEval_EvalFrameDefault; #ifdef HAVE_DLOPEN -- cgit v0.12