bpo-39465: Fix _PyUnicode_FromId() for subinterpreters (GH-20058)

Make _PyUnicode_FromId() function compatible with subinterpreters.
Each interpreter now has an array of identifier objects (interned
strings decoded from UTF-8).

* Add PyInterpreterState.unicode.identifiers: array of identifiers
  objects.
* Add _PyRuntimeState.unicode_ids used to allocate unique indexes
  to _Py_Identifier.
* Rewrite the _Py_Identifier structure.

Microbenchmark on _PyUnicode_FromId(&PyId_a) with _Py_IDENTIFIER(a):

[ref] 2.42 ns +- 0.00 ns -> [atomic] 3.39 ns +- 0.00 ns: 1.40x slower

This change adds 1 ns per _PyUnicode_FromId() call in average.
This commit is contained in:
Victor Stinner 2020-12-26 00:41:46 +01:00 committed by GitHub
parent f0853bcedf
commit ba3d67c2fb
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 102 additions and 37 deletions

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@ -35,12 +35,13 @@ PyAPI_FUNC(Py_ssize_t) _Py_GetRefTotal(void);
_PyObject_{Get,Set,Has}AttrId are __getattr__ versions using _Py_Identifier*.
*/
typedef struct _Py_Identifier {
struct _Py_Identifier *next;
const char* string;
PyObject *object;
// Index in PyInterpreterState.unicode.ids.array. It is process-wide
// unique and must be initialized to -1.
Py_ssize_t index;
} _Py_Identifier;
#define _Py_static_string_init(value) { .next = NULL, .string = value, .object = NULL }
#define _Py_static_string_init(value) { .string = value, .index = -1 }
#define _Py_static_string(varname, value) static _Py_Identifier varname = _Py_static_string_init(value)
#define _Py_IDENTIFIER(varname) _Py_static_string(PyId_##varname, #varname)

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@ -64,6 +64,11 @@ struct _Py_bytes_state {
PyBytesObject *characters[256];
};
struct _Py_unicode_ids {
Py_ssize_t size;
PyObject **array;
};
struct _Py_unicode_state {
// The empty Unicode object is a singleton to improve performance.
PyObject *empty_string;
@ -71,6 +76,8 @@ struct _Py_unicode_state {
shared as well. */
PyObject *latin1[256];
struct _Py_unicode_fs_codec fs_codec;
// Unicode identifiers (_Py_Identifier): see _PyUnicode_FromId()
struct _Py_unicode_ids ids;
};
struct _Py_float_state {

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@ -49,6 +49,11 @@ typedef struct _Py_AuditHookEntry {
void *userData;
} _Py_AuditHookEntry;
struct _Py_unicode_runtime_ids {
PyThread_type_lock lock;
Py_ssize_t next_index;
};
/* Full Python runtime state */
typedef struct pyruntimestate {
@ -106,6 +111,8 @@ typedef struct pyruntimestate {
void *open_code_userdata;
_Py_AuditHookEntry *audit_hook_head;
struct _Py_unicode_runtime_ids unicode_ids;
// XXX Consolidate globals found via the check-c-globals script.
} _PyRuntimeState;

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@ -0,0 +1,3 @@
Make :c:func:`_PyUnicode_FromId` function compatible with subinterpreters.
Each interpreter now has an array of identifier objects (interned strings
decoded from UTF-8). Patch by Victor Stinner.

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@ -41,6 +41,7 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
#define PY_SSIZE_T_CLEAN
#include "Python.h"
#include "pycore_abstract.h" // _PyIndex_Check()
#include "pycore_atomic_funcs.h" // _Py_atomic_size_get()
#include "pycore_bytes_methods.h" // _Py_bytes_lower()
#include "pycore_format.h" // F_LJUST
#include "pycore_initconfig.h" // _PyStatus_OK()
@ -302,9 +303,6 @@ unicode_decode_utf8(const char *s, Py_ssize_t size,
_Py_error_handler error_handler, const char *errors,
Py_ssize_t *consumed);
/* List of static strings. */
static _Py_Identifier *static_strings = NULL;
/* Fast detection of the most frequent whitespace characters */
const unsigned char _Py_ascii_whitespace[] = {
0, 0, 0, 0, 0, 0, 0, 0,
@ -2312,42 +2310,85 @@ PyUnicode_FromString(const char *u)
return PyUnicode_DecodeUTF8Stateful(u, (Py_ssize_t)size, NULL, NULL);
}
PyObject *
_PyUnicode_FromId(_Py_Identifier *id)
{
if (id->object) {
return id->object;
PyInterpreterState *interp = _PyInterpreterState_GET();
struct _Py_unicode_ids *ids = &interp->unicode.ids;
int index = _Py_atomic_size_get(&id->index);
if (index < 0) {
struct _Py_unicode_runtime_ids *rt_ids = &interp->runtime->unicode_ids;
PyThread_acquire_lock(rt_ids->lock, WAIT_LOCK);
// Check again to detect concurrent access. Another thread can have
// initialized the index while this thread waited for the lock.
index = _Py_atomic_size_get(&id->index);
if (index < 0) {
assert(rt_ids->next_index < PY_SSIZE_T_MAX);
index = rt_ids->next_index;
rt_ids->next_index++;
_Py_atomic_size_set(&id->index, index);
}
PyThread_release_lock(rt_ids->lock);
}
assert(index >= 0);
PyObject *obj;
obj = PyUnicode_DecodeUTF8Stateful(id->string,
strlen(id->string),
if (index < ids->size) {
obj = ids->array[index];
if (obj) {
// Return a borrowed reference
return obj;
}
}
obj = PyUnicode_DecodeUTF8Stateful(id->string, strlen(id->string),
NULL, NULL);
if (!obj) {
return NULL;
}
PyUnicode_InternInPlace(&obj);
assert(!id->next);
id->object = obj;
id->next = static_strings;
static_strings = id;
return id->object;
if (index >= ids->size) {
// Overallocate to reduce the number of realloc
Py_ssize_t new_size = Py_MAX(index * 2, 16);
Py_ssize_t item_size = sizeof(ids->array[0]);
PyObject **new_array = PyMem_Realloc(ids->array, new_size * item_size);
if (new_array == NULL) {
PyErr_NoMemory();
return NULL;
}
memset(&new_array[ids->size], 0, (new_size - ids->size) * item_size);
ids->array = new_array;
ids->size = new_size;
}
// The array stores a strong reference
ids->array[index] = obj;
// Return a borrowed reference
return obj;
}
static void
unicode_clear_static_strings(void)
unicode_clear_identifiers(PyThreadState *tstate)
{
_Py_Identifier *tmp, *s = static_strings;
while (s) {
Py_CLEAR(s->object);
tmp = s->next;
s->next = NULL;
s = tmp;
PyInterpreterState *interp = _PyInterpreterState_GET();
struct _Py_unicode_ids *ids = &interp->unicode.ids;
for (Py_ssize_t i=0; i < ids->size; i++) {
Py_XDECREF(ids->array[i]);
}
static_strings = NULL;
ids->size = 0;
PyMem_Free(ids->array);
ids->array = NULL;
// Don't reset _PyRuntime next_index: _Py_Identifier.id remains valid
// after Py_Finalize().
}
/* Internal function, doesn't check maximum character */
PyObject*
@ -16238,9 +16279,7 @@ _PyUnicode_Fini(PyThreadState *tstate)
Py_CLEAR(state->latin1[i]);
}
if (_Py_IsMainInterpreter(tstate)) {
unicode_clear_static_strings();
}
unicode_clear_identifiers(tstate);
_PyUnicode_FiniEncodings(&tstate->interp->unicode.fs_codec);
}

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@ -73,18 +73,24 @@ _PyRuntimeState_Init_impl(_PyRuntimeState *runtime)
runtime->interpreters.mutex = PyThread_allocate_lock();
if (runtime->interpreters.mutex == NULL) {
return _PyStatus_ERR("Can't initialize threads for interpreter");
return _PyStatus_NO_MEMORY();
}
runtime->interpreters.next_id = -1;
runtime->xidregistry.mutex = PyThread_allocate_lock();
if (runtime->xidregistry.mutex == NULL) {
return _PyStatus_ERR("Can't initialize threads for cross-interpreter data registry");
return _PyStatus_NO_MEMORY();
}
// Set it to the ID of the main thread of the main interpreter.
runtime->main_thread = PyThread_get_thread_ident();
runtime->unicode_ids.lock = PyThread_allocate_lock();
if (runtime->unicode_ids.lock == NULL) {
return _PyStatus_NO_MEMORY();
}
runtime->unicode_ids.next_index = 0;
return _PyStatus_OK();
}
@ -108,17 +114,17 @@ _PyRuntimeState_Fini(_PyRuntimeState *runtime)
/* Force the allocator used by _PyRuntimeState_Init(). */
PyMemAllocatorEx old_alloc;
_PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
if (runtime->interpreters.mutex != NULL) {
PyThread_free_lock(runtime->interpreters.mutex);
runtime->interpreters.mutex = NULL;
#define FREE_LOCK(LOCK) \
if (LOCK != NULL) { \
PyThread_free_lock(LOCK); \
LOCK = NULL; \
}
if (runtime->xidregistry.mutex != NULL) {
PyThread_free_lock(runtime->xidregistry.mutex);
runtime->xidregistry.mutex = NULL;
}
FREE_LOCK(runtime->interpreters.mutex);
FREE_LOCK(runtime->xidregistry.mutex);
FREE_LOCK(runtime->unicode_ids.lock);
#undef FREE_LOCK
PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
}
@ -139,12 +145,14 @@ _PyRuntimeState_ReInitThreads(_PyRuntimeState *runtime)
int reinit_interp = _PyThread_at_fork_reinit(&runtime->interpreters.mutex);
int reinit_main_id = _PyThread_at_fork_reinit(&runtime->interpreters.main->id_mutex);
int reinit_xidregistry = _PyThread_at_fork_reinit(&runtime->xidregistry.mutex);
int reinit_unicode_ids = _PyThread_at_fork_reinit(&runtime->unicode_ids.lock);
PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
if (reinit_interp < 0
|| reinit_main_id < 0
|| reinit_xidregistry < 0)
|| reinit_xidregistry < 0
|| reinit_unicode_ids < 0)
{
return _PyStatus_ERR("Failed to reinitialize runtime locks");