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bpo-40521: Optimize PyBytes_FromStringAndSize(str, 0) (GH-21142) 

Always create the empty bytes string singleton.

Optimize PyBytes_FromStringAndSize(str, 0): it no longer has to check
if the empty string singleton was created or not, it is always
available.

Add functions:

* _PyBytes_Init()
* bytes_get_empty(), bytes_new_empty()
* bytes_create_empty_string_singleton()
* unicode_create_empty_string_singleton()

_Py_unicode_state: rename empty structure member to empty_string.
This commit is contained in:
Victor Stinner 2020-06-25 14:07:40 +02:00 committed by GitHub
parent 0f8ec1fff0
commit 91698d8caa
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
5 changed files with 107 additions and 53 deletions
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4
Include/internal/pycore_interp.h
View File

@ -66,13 +66,13 @@ struct _Py_unicode_fs_codec {
};
struct _Py_bytes_state {
PyObject *empty_string;
PyBytesObject *characters[256];
PyBytesObject *empty_string;
};
struct _Py_unicode_state {
// The empty Unicode object is a singleton to improve performance.
PyObject *empty;
PyObject *empty_string;
/* Single character Unicode strings in the Latin-1 range are being
shared as well. */
PyObject *latin1[256];

1
Include/internal/pycore_pylifecycle.h
View File

@ -32,6 +32,7 @@ PyAPI_FUNC(int) _Py_IsLocaleCoercionTarget(const char *ctype_loc);
/* Various one-time initializers */
extern PyStatus _PyUnicode_Init(PyThreadState *tstate);
extern PyStatus _PyBytes_Init(PyThreadState *tstate);
extern int _PyStructSequence_Init(void);
extern int _PyLong_Init(PyThreadState *tstate);
extern PyStatus _PyTuple_Init(PyThreadState *tstate);

91
Objects/bytesobject.c
View File

@ -4,8 +4,9 @@
#include "Python.h"
#include "pycore_abstract.h" // _PyIndex_Check()
#include "pycore_bytes_methods.h"
#include "pycore_object.h"
#include "pycore_bytes_methods.h" // _Py_bytes_startswith()
#include "pycore_initconfig.h" // _PyStatus_OK()
#include "pycore_object.h" // _PyObject_GC_TRACK
#include "pycore_pymem.h" // PYMEM_CLEANBYTE
#include "pystrhex.h"
@ -41,6 +42,44 @@ get_bytes_state(void)
}
// Return a borrowed reference to the empty bytes string singleton.
static inline PyObject* bytes_get_empty(void)
{
struct _Py_bytes_state *state = get_bytes_state();
// bytes_get_empty() must not be called before _PyBytes_Init()
// or after _PyBytes_Fini()
assert(state->empty_string != NULL);
return state->empty_string;
}
// Return a strong reference to the empty bytes string singleton.
static inline PyObject* bytes_new_empty(void)
{
PyObject *empty = bytes_get_empty();
Py_INCREF(empty);
return (PyObject *)empty;
}
static int
bytes_create_empty_string_singleton(struct _Py_bytes_state *state)
{
// Create the empty bytes string singleton
PyBytesObject *op = (PyBytesObject *)PyObject_Malloc(PyBytesObject_SIZE);
if (op == NULL) {
return -1;
}
_PyObject_InitVar((PyVarObject*)op, &PyBytes_Type, 0);
op->ob_shash = -1;
op->ob_sval[0] = '\0';
assert(state->empty_string == NULL);
state->empty_string = (PyObject *)op;
return 0;
}
/*
For PyBytes_FromString(), the parameter `str' points to a null-terminated
string containing exactly `size' bytes.
@ -70,12 +109,7 @@ _PyBytes_FromSize(Py_ssize_t size, int use_calloc)
assert(size >= 0);
if (size == 0) {
struct _Py_bytes_state *state = get_bytes_state();
op = state->empty_string;
if (op != NULL) {
Py_INCREF(op);
return (PyObject *)op;
}
return bytes_new_empty();
}
if ((size_t)size > (size_t)PY_SSIZE_T_MAX - PyBytesObject_SIZE) {
@ -94,13 +128,8 @@ _PyBytes_FromSize(Py_ssize_t size, int use_calloc)
}
_PyObject_InitVar((PyVarObject*)op, &PyBytes_Type, size);
op->ob_shash = -1;
if (!use_calloc)
if (!use_calloc) {
op->ob_sval[size] = '\0';
/* empty byte string singleton */
if (size == 0) {
struct _Py_bytes_state *state = get_bytes_state();
Py_INCREF(op);
state->empty_string = op;
}
return (PyObject *) op;
}
@ -122,6 +151,9 @@ PyBytes_FromStringAndSize(const char *str, Py_ssize_t size)
return (PyObject *)op;
}
}
if (size == 0) {
return bytes_new_empty();
}
op = (PyBytesObject *)_PyBytes_FromSize(size, 0);
if (op == NULL)
@ -155,11 +187,7 @@ PyBytes_FromString(const char *str)
struct _Py_bytes_state *state = get_bytes_state();
if (size == 0) {
op = state->empty_string;
if (op != NULL) {
Py_INCREF(op);
return (PyObject *)op;
}
return bytes_new_empty();
}
else if (size == 1) {
op = state->characters[*str & UCHAR_MAX];
@ -178,11 +206,8 @@ PyBytes_FromString(const char *str)
op->ob_shash = -1;
memcpy(op->ob_sval, str, size+1);
/* share short strings */
if (size == 0) {
Py_INCREF(op);
state->empty_string = op;
}
else if (size == 1) {
if (size == 1) {
assert(state->characters[*str & UCHAR_MAX] == NULL);
Py_INCREF(op);
state->characters[*str & UCHAR_MAX] = op;
}
@ -1272,7 +1297,7 @@ PyBytes_AsStringAndSize(PyObject *obj,
/* -------------------------------------------------------------------- */
/* Methods */
#define STRINGLIB_GET_EMPTY() get_bytes_state()->empty_string
#define STRINGLIB_GET_EMPTY() bytes_get_empty()
#include "stringlib/stringdefs.h"
@ -3053,9 +3078,9 @@ _PyBytes_Resize(PyObject **pv, Py_ssize_t newsize)
goto error;
}
if (newsize == 0) {
*pv = _PyBytes_FromSize(0, 0);
*pv = bytes_new_empty();
Py_DECREF(v);
return (*pv == NULL) ? -1 : 0;
return 0;
}
/* XXX UNREF/NEWREF interface should be more symmetrical */
#ifdef Py_REF_DEBUG
@ -3084,6 +3109,18 @@ error:
return -1;
}
PyStatus
_PyBytes_Init(PyThreadState *tstate)
{
struct _Py_bytes_state *state = &tstate->interp->bytes;
if (bytes_create_empty_string_singleton(state) < 0) {
return _PyStatus_NO_MEMORY();
}
return _PyStatus_OK();
}
void
_PyBytes_Fini(PyThreadState *tstate)
{

59
Objects/unicodeobject.c
View File

@ -41,16 +41,15 @@ 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_bytes_methods.h"
#include "pycore_fileutils.h"
#include "pycore_initconfig.h"
#include "pycore_bytes_methods.h" // _Py_bytes_lower()
#include "pycore_initconfig.h" // _PyStatus_OK()
#include "pycore_interp.h" // PyInterpreterState.fs_codec
#include "pycore_object.h"
#include "pycore_pathconfig.h"
#include "pycore_pylifecycle.h"
#include "pycore_object.h" // _PyObject_GC_TRACK()
#include "pycore_pathconfig.h" // _Py_DumpPathConfig()
#include "pycore_pylifecycle.h" // _Py_SetFileSystemEncoding()
#include "pycore_pystate.h" // _PyInterpreterState_GET()
#include "ucnhash.h"
#include "stringlib/eq.h"
#include "ucnhash.h" // _PyUnicode_Name_CAPI
#include "stringlib/eq.h" // unicode_eq()
#ifdef MS_WINDOWS
#include <windows.h>
@ -236,10 +235,12 @@ static inline PyObject* unicode_get_empty(void)
struct _Py_unicode_state *state = get_unicode_state();
// unicode_get_empty() must not be called before _PyUnicode_Init()
// or after _PyUnicode_Fini()
assert(state->empty != NULL);
return state->empty;
assert(state->empty_string != NULL);
return state->empty_string;
}
// Return a strong reference to the empty string singleton.
static inline PyObject* unicode_new_empty(void)
{
PyObject *empty = unicode_get_empty();
@ -1385,6 +1386,26 @@ _PyUnicode_Dump(PyObject *op)
}
#endif
static int
unicode_create_empty_string_singleton(struct _Py_unicode_state *state)
{
// Use size=1 rather than size=0, so PyUnicode_New(0, maxchar) can be
// optimized to always use state->empty_string without having to check if
// it is NULL or not.
PyObject *empty = PyUnicode_New(1, 0);
if (empty == NULL) {
return -1;
}
PyUnicode_1BYTE_DATA(empty)[0] = 0;
_PyUnicode_LENGTH(empty) = 0;
assert(_PyUnicode_CheckConsistency(empty, 1));
assert(state->empty_string == NULL);
state->empty_string = empty;
return 0;
}
PyObject *
PyUnicode_New(Py_ssize_t size, Py_UCS4 maxchar)
{
@ -1972,7 +1993,7 @@ static int
unicode_is_singleton(PyObject *unicode)
{
struct _Py_unicode_state *state = get_unicode_state();
if (unicode == state->empty) {
if (unicode == state->empty_string) {
return 1;
}
PyASCIIObject *ascii = (PyASCIIObject *)unicode;
@ -15542,20 +15563,10 @@ _PyUnicode_Init(PyThreadState *tstate)
0x2029, /* PARAGRAPH SEPARATOR */
};
// Use size=1 rather than size=0, so PyUnicode_New(0, maxchar) can be
// optimized to always use state->empty without having to check if it is
// NULL or not.
PyObject *empty = PyUnicode_New(1, 0);
if (empty == NULL) {
struct _Py_unicode_state *state = &tstate->interp->unicode;
if (unicode_create_empty_string_singleton(state) < 0) {
return _PyStatus_NO_MEMORY();
}
PyUnicode_1BYTE_DATA(empty)[0] = 0;
_PyUnicode_LENGTH(empty) = 0;
assert(_PyUnicode_CheckConsistency(empty, 1));
struct _Py_unicode_state *state = &tstate->interp->unicode;
assert(state->empty == NULL);
state->empty = empty;
if (_Py_IsMainInterpreter(tstate)) {
/* initialize the linebreak bloom filter */
@ -16223,7 +16234,7 @@ _PyUnicode_Fini(PyThreadState *tstate)
#endif /* __INSURE__ */
}
Py_CLEAR(state->empty);
Py_CLEAR(state->empty_string);
for (Py_ssize_t i = 0; i < 256; i++) {
Py_CLEAR(state->latin1[i]);

5
Python/pylifecycle.c
View File

@ -607,6 +607,11 @@ pycore_init_types(PyThreadState *tstate)
return status;
}
status = _PyBytes_Init(tstate);
if (_PyStatus_EXCEPTION(status)) {
return status;
}
status = _PyExc_Init(tstate);
if (_PyStatus_EXCEPTION(status)) {
return status;