bpo-41756: Introduce PyGen_Send C API (GH-22196)
The new API allows to efficiently send values into native generators and coroutines avoiding use of StopIteration exceptions to signal returns. ceval loop now uses this method instead of the old "private" _PyGen_Send C API. This translates to 1.6x increased performance of 'await' calls in micro-benchmarks. Aside from CPython core improvements, this new API will also allow Cython to generate more efficient code, benefiting high-performance IO libraries like uvloop.
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ec8a15b034
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2b05361bf7
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@ -15,6 +15,11 @@ than explicitly calling :c:func:`PyGen_New` or :c:func:`PyGen_NewWithQualName`.
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The C structure used for generator objects.
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.. c:type:: PySendResult
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The enum value used to represent different results of :c:func:`PyGen_Send`.
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.. c:var:: PyTypeObject PyGen_Type
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The type object corresponding to generator objects.
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@ -42,3 +47,13 @@ than explicitly calling :c:func:`PyGen_New` or :c:func:`PyGen_NewWithQualName`.
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with ``__name__`` and ``__qualname__`` set to *name* and *qualname*.
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A reference to *frame* is stolen by this function. The *frame* argument
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must not be ``NULL``.
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.. c:function:: PySendResult PyGen_Send(PyGenObject *gen, PyObject *arg, PyObject **presult)
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Sends the *arg* value into the generator *gen*. Coroutine objects
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are also allowed to be as the *gen* argument but they need to be
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explicitly casted to PyGenObject*. Returns:
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- ``PYGEN_RETURN`` if generator returns. Return value is returned via *presult*.
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- ``PYGEN_NEXT`` if generator yields. Yielded value is returned via *presult*.
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- ``PYGEN_ERROR`` if generator has raised and exception. *presult* is set to ``NULL``.
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@ -959,6 +959,11 @@ PyGen_NewWithQualName:PyFrameObject*:frame:0:
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PyGen_NewWithQualName:PyObject*:name:0:
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PyGen_NewWithQualName:PyObject*:qualname:0:
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PyGen_Send:int:::
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PyGen_Send:PyGenObject*:gen:0:
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PyGen_Send:PyObject*:arg:0:
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PyGen_Send:PyObject**:presult:+1:
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PyCoro_CheckExact:int:::
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PyCoro_CheckExact:PyObject*:ob:0:
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@ -45,6 +45,21 @@ PyAPI_FUNC(PyObject *) _PyGen_Send(PyGenObject *, PyObject *);
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PyObject *_PyGen_yf(PyGenObject *);
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PyAPI_FUNC(void) _PyGen_Finalize(PyObject *self);
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typedef enum {
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PYGEN_RETURN = 0,
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PYGEN_ERROR = -1,
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PYGEN_NEXT = 1,
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} PySendResult;
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/* Sends the value into the generator or the coroutine. Returns:
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- PYGEN_RETURN (0) if generator has returned.
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'result' parameter is filled with return value
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- PYGEN_ERROR (-1) if exception was raised.
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'result' parameter is NULL
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- PYGEN_NEXT (1) if generator has yielded.
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'result' parameter is filled with yielded value. */
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PyAPI_FUNC(PySendResult) PyGen_Send(PyGenObject *, PyObject *, PyObject **);
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#ifndef Py_LIMITED_API
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typedef struct {
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_PyGenObject_HEAD(cr)
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@ -0,0 +1,2 @@
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Add PyGen_Send function to allow sending value into generator/coroutine
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without raising StopIteration exception to signal return
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@ -2621,6 +2621,20 @@ task_set_error_soon(TaskObj *task, PyObject *et, const char *format, ...)
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Py_RETURN_NONE;
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}
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static inline int
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gen_status_from_result(PyObject **result)
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{
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if (*result != NULL) {
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return PYGEN_NEXT;
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}
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if (_PyGen_FetchStopIterationValue(result) == 0) {
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return PYGEN_RETURN;
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}
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assert(PyErr_Occurred());
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return PYGEN_ERROR;
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}
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static PyObject *
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task_step_impl(TaskObj *task, PyObject *exc)
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{
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@ -2679,26 +2693,29 @@ task_step_impl(TaskObj *task, PyObject *exc)
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return NULL;
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}
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int gen_status = PYGEN_ERROR;
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if (exc == NULL) {
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if (PyGen_CheckExact(coro) || PyCoro_CheckExact(coro)) {
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result = _PyGen_Send((PyGenObject*)coro, Py_None);
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gen_status = PyGen_Send((PyGenObject*)coro, Py_None, &result);
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}
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else {
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result = _PyObject_CallMethodIdOneArg(coro, &PyId_send, Py_None);
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gen_status = gen_status_from_result(&result);
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}
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}
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else {
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result = _PyObject_CallMethodIdOneArg(coro, &PyId_throw, exc);
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gen_status = gen_status_from_result(&result);
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if (clear_exc) {
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/* We created 'exc' during this call */
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Py_DECREF(exc);
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}
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}
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if (result == NULL) {
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if (gen_status == PYGEN_RETURN || gen_status == PYGEN_ERROR) {
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PyObject *et, *ev, *tb;
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if (_PyGen_FetchStopIterationValue(&o) == 0) {
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if (result != NULL) {
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/* The error is StopIteration and that means that
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the underlying coroutine has resolved */
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@ -2709,10 +2726,10 @@ task_step_impl(TaskObj *task, PyObject *exc)
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res = future_cancel((FutureObj*)task, task->task_cancel_msg);
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}
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else {
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res = future_set_result((FutureObj*)task, o);
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res = future_set_result((FutureObj*)task, result);
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}
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Py_DECREF(o);
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Py_DECREF(result);
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if (res == NULL) {
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return NULL;
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@ -137,7 +137,7 @@ gen_dealloc(PyGenObject *gen)
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}
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static PyObject *
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gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing)
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gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing, int *is_return_value)
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{
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PyThreadState *tstate = _PyThreadState_GET();
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PyFrameObject *f = gen->gi_frame;
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@ -170,6 +170,10 @@ gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing)
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PyErr_SetNone(PyExc_StopAsyncIteration);
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}
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else {
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if (is_return_value != NULL) {
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*is_return_value = 1;
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Py_RETURN_NONE;
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}
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PyErr_SetNone(PyExc_StopIteration);
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}
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}
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@ -230,18 +234,33 @@ gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing)
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/* Delay exception instantiation if we can */
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if (PyAsyncGen_CheckExact(gen)) {
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PyErr_SetNone(PyExc_StopAsyncIteration);
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Py_CLEAR(result);
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}
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else if (arg) {
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/* Set exception if not called by gen_iternext() */
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PyErr_SetNone(PyExc_StopIteration);
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if (is_return_value != NULL) {
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*is_return_value = 1;
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}
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else {
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/* Set exception if not called by gen_iternext() */
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PyErr_SetNone(PyExc_StopIteration);
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Py_CLEAR(result);
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}
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}
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else {
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Py_CLEAR(result);
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}
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}
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else {
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/* Async generators cannot return anything but None */
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assert(!PyAsyncGen_CheckExact(gen));
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_PyGen_SetStopIterationValue(result);
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if (is_return_value != NULL) {
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*is_return_value = 1;
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}
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else {
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_PyGen_SetStopIterationValue(result);
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Py_CLEAR(result);
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}
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}
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Py_CLEAR(result);
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}
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else if (!result && PyErr_ExceptionMatches(PyExc_StopIteration)) {
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const char *msg = "generator raised StopIteration";
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_PyErr_FormatFromCause(PyExc_RuntimeError, "%s", msg);
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}
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if (!result || _PyFrameHasCompleted(f)) {
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if ((is_return_value && *is_return_value) || !result || _PyFrameHasCompleted(f)) {
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/* generator can't be rerun, so release the frame */
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/* first clean reference cycle through stored exception traceback */
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_PyErr_ClearExcState(&gen->gi_exc_state);
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@ -283,7 +302,19 @@ return next yielded value or raise StopIteration.");
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PyObject *
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_PyGen_Send(PyGenObject *gen, PyObject *arg)
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{
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return gen_send_ex(gen, arg, 0, 0);
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return gen_send_ex(gen, arg, 0, 0, NULL);
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}
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PySendResult
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PyGen_Send(PyGenObject *gen, PyObject *arg, PyObject **result)
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{
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assert(result != NULL);
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int is_return_value = 0;
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if ((*result = gen_send_ex(gen, arg, 0, 0, &is_return_value)) == NULL) {
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return PYGEN_ERROR;
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}
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return is_return_value ? PYGEN_RETURN : PYGEN_NEXT;
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}
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PyDoc_STRVAR(close_doc,
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@ -365,7 +396,7 @@ gen_close(PyGenObject *gen, PyObject *args)
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}
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if (err == 0)
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PyErr_SetNone(PyExc_GeneratorExit);
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retval = gen_send_ex(gen, Py_None, 1, 1);
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retval = gen_send_ex(gen, Py_None, 1, 1, NULL);
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if (retval) {
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const char *msg = "generator ignored GeneratorExit";
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if (PyCoro_CheckExact(gen)) {
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@ -413,7 +444,7 @@ _gen_throw(PyGenObject *gen, int close_on_genexit,
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gen->gi_frame->f_state = state;
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Py_DECREF(yf);
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if (err < 0)
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return gen_send_ex(gen, Py_None, 1, 0);
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return gen_send_ex(gen, Py_None, 1, 0, NULL);
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goto throw_here;
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}
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if (PyGen_CheckExact(yf) || PyCoro_CheckExact(yf)) {
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assert(gen->gi_frame->f_lasti >= 0);
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gen->gi_frame->f_lasti += sizeof(_Py_CODEUNIT);
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if (_PyGen_FetchStopIterationValue(&val) == 0) {
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ret = gen_send_ex(gen, val, 0, 0);
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ret = gen_send_ex(gen, val, 0, 0, NULL);
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Py_DECREF(val);
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} else {
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ret = gen_send_ex(gen, Py_None, 1, 0);
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ret = gen_send_ex(gen, Py_None, 1, 0, NULL);
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}
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}
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return ret;
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@ -522,7 +553,7 @@ throw_here:
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}
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PyErr_Restore(typ, val, tb);
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return gen_send_ex(gen, Py_None, 1, 0);
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return gen_send_ex(gen, Py_None, 1, 0, NULL);
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failed_throw:
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/* Didn't use our arguments, so restore their original refcounts */
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@ -551,7 +582,7 @@ gen_throw(PyGenObject *gen, PyObject *args)
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static PyObject *
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gen_iternext(PyGenObject *gen)
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{
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return gen_send_ex(gen, NULL, 0, 0);
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return gen_send_ex(gen, NULL, 0, 0, NULL);
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}
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/*
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static PyObject *
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coro_wrapper_iternext(PyCoroWrapper *cw)
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{
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return gen_send_ex((PyGenObject *)cw->cw_coroutine, NULL, 0, 0);
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return gen_send_ex((PyGenObject *)cw->cw_coroutine, NULL, 0, 0, NULL);
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}
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static PyObject *
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coro_wrapper_send(PyCoroWrapper *cw, PyObject *arg)
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{
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return gen_send_ex((PyGenObject *)cw->cw_coroutine, arg, 0, 0);
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return gen_send_ex((PyGenObject *)cw->cw_coroutine, arg, 0, 0, NULL);
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}
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static PyObject *
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@ -1570,7 +1601,7 @@ async_gen_asend_send(PyAsyncGenASend *o, PyObject *arg)
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}
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o->ags_gen->ag_running_async = 1;
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result = gen_send_ex((PyGenObject*)o->ags_gen, arg, 0, 0);
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result = gen_send_ex((PyGenObject*)o->ags_gen, arg, 0, 0, NULL);
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result = async_gen_unwrap_value(o->ags_gen, result);
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if (result == NULL) {
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@ -1926,7 +1957,7 @@ async_gen_athrow_send(PyAsyncGenAThrow *o, PyObject *arg)
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assert(o->agt_state == AWAITABLE_STATE_ITER);
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retval = gen_send_ex((PyGenObject *)gen, arg, 0, 0);
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retval = gen_send_ex((PyGenObject *)gen, arg, 0, 0, NULL);
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if (o->agt_args) {
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return async_gen_unwrap_value(o->agt_gen, retval);
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} else {
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@ -2223,29 +2223,53 @@ main_loop:
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case TARGET(YIELD_FROM): {
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PyObject *v = POP();
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PyObject *receiver = TOP();
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int err;
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if (PyGen_CheckExact(receiver) || PyCoro_CheckExact(receiver)) {
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retval = _PyGen_Send((PyGenObject *)receiver, v);
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int is_gen_or_coro = PyGen_CheckExact(receiver) || PyCoro_CheckExact(receiver);
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int gen_status;
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if (tstate->c_tracefunc == NULL && is_gen_or_coro) {
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gen_status = PyGen_Send((PyGenObject *)receiver, v, &retval);
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} else {
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_Py_IDENTIFIER(send);
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if (v == Py_None)
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retval = Py_TYPE(receiver)->tp_iternext(receiver);
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else
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retval = _PyObject_CallMethodIdOneArg(receiver, &PyId_send, v);
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if (is_gen_or_coro) {
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retval = _PyGen_Send((PyGenObject *)receiver, v);
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}
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else {
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_Py_IDENTIFIER(send);
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if (v == Py_None) {
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retval = Py_TYPE(receiver)->tp_iternext(receiver);
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}
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else {
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retval = _PyObject_CallMethodIdOneArg(receiver, &PyId_send, v);
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}
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}
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if (retval == NULL) {
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if (tstate->c_tracefunc != NULL
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&& _PyErr_ExceptionMatches(tstate, PyExc_StopIteration))
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call_exc_trace(tstate->c_tracefunc, tstate->c_traceobj, tstate, f);
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if (_PyGen_FetchStopIterationValue(&retval) == 0) {
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gen_status = PYGEN_RETURN;
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}
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else {
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gen_status = PYGEN_ERROR;
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}
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}
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else {
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gen_status = PYGEN_NEXT;
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}
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}
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Py_DECREF(v);
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if (retval == NULL) {
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PyObject *val;
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if (tstate->c_tracefunc != NULL
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&& _PyErr_ExceptionMatches(tstate, PyExc_StopIteration))
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call_exc_trace(tstate->c_tracefunc, tstate->c_traceobj, tstate, f);
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err = _PyGen_FetchStopIterationValue(&val);
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if (err < 0)
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goto error;
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if (gen_status == PYGEN_ERROR) {
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assert (retval == NULL);
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goto error;
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}
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if (gen_status == PYGEN_RETURN) {
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assert (retval != NULL);
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Py_DECREF(receiver);
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SET_TOP(val);
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SET_TOP(retval);
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retval = NULL;
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DISPATCH();
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}
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assert (gen_status == PYGEN_NEXT);
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/* receiver remains on stack, retval is value to be yielded */
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/* and repeat... */
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assert(f->f_lasti >= (int)sizeof(_Py_CODEUNIT));
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