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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.
This commit is contained in:
Victor Stinner 2020-12-26 01:45:43 +01:00 committed by GitHub
parent 77fde8dc16
commit 4101018488
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 136 additions and 90 deletions
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22
Include/internal/pycore_interp.h
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@ -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);

3
Include/internal/pycore_object.h
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@ -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().

2
Include/internal/pycore_pylifecycle.h
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@ -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);

1
Misc/NEWS.d/next/Core and Builtins/2020-12-25-23-30-58.bpo-42745.XsFoHS.rst Normal file
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@ -0,0 +1 @@
Make the type attribute lookup cache per-interpreter. Patch by Victor Stinner.

194
Objects/typeobject.c
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@ -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
(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 */
};
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);
}
static struct type_cache*
get_type_cache(void)
{
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 = cache->hits + cache->collisions + cache->misses;
fprintf(stderr, "-- Method cache hits = %zd (%d%%)\n",
cache->hits, (int) (100.0 * cache->hits / total));
fprintf(stderr, "-- Method cache true misses = %zd (%d%%)\n",
cache->misses, (int) (100.0 * cache->misses / total));
fprintf(stderr, "-- Method cache collisions = %zd (%d%%)\n",
cache->collisions, (int) (100.0 * cache->collisions / total));
fprintf(stderr, "-- Method cache size = %zd KiB\n",
sizeof(cache->hashtable) / 1024);
#endif
unsigned int cur_version_tag = next_version_tag - 1;
next_version_tag = 0;
type_cache_clear(cache, 0);
return cur_version_tag;
}
unsigned int
PyType_ClearCache(void)
{
#ifdef MCACHE
Py_ssize_t i;
unsigned int cur_version_tag = next_version_tag - 1;
#if MCACHE_STATS
size_t total = method_cache_hits + method_cache_collisions + method_cache_misses;
fprintf(stderr, "-- Method cache hits = %zd (%d%%)\n",
method_cache_hits, (int) (100.0 * method_cache_hits / total));
fprintf(stderr, "-- Method cache true misses = %zd (%d%%)\n",
method_cache_misses, (int) (100.0 * method_cache_misses / total));
fprintf(stderr, "-- Method cache collisions = %zd (%d%%)\n",
method_cache_collisions, (int) (100.0 * method_cache_collisions / total));
fprintf(stderr, "-- Method cache size = %zd KiB\n",
sizeof(method_cache) / 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;
}
next_version_tag = 0;
/* mark all version tags as invalid */
PyType_Modified(&PyBaseObject_Type);
return cur_version_tag;
#else
return 0;
#endif
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;
}

2
Python/pylifecycle.c
View File

@ -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();

2
Python/pystate.c
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@ -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