bpo-44590: Lazily allocate frame objects (GH-27077)

* Convert "specials" array to InterpreterFrame struct, adding f_lasti, f_state and other non-debug FrameObject fields to it. * Refactor, calls pushing the call to the interpreter upward toward _PyEval_Vector. * Compute f_back when on thread stack, only filling in value when frame object outlives stack invocation. * Move ownership of InterpreterFrame in generator from frame object to generator object. * Do not create frame objects for Python calls. * Do not create frame objects for generators.

Author: markshannon

Include/cpython/ceval.h

@@ -19,7 +19,7 @@ PyAPI_FUNC(PyObject *) _PyEval_GetBuiltinId(_Py_Identifier *);
  flag was set, else return 0. */
 PyAPI_FUNC(int) PyEval_MergeCompilerFlags(PyCompilerFlags *cf);
 
-PyAPI_FUNC(PyObject *) _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int exc);
+PyAPI_FUNC(PyObject *) _PyEval_EvalFrameDefault(PyThreadState *tstate, struct _interpreter_frame *f, int exc);
 
 PyAPI_FUNC(void) _PyEval_SetSwitchInterval(unsigned long microseconds);
 PyAPI_FUNC(unsigned long) _PyEval_GetSwitchInterval(void);

Include/cpython/frameobject.h

@@ -4,50 +4,17 @@
 # error "this header file must not be included directly"
 #endif
 
-/* These values are chosen so that the inline functions below all
- * compare f_state to zero.
- */
-enum _framestate {
- FRAME_CREATED = -2,
- FRAME_SUSPENDED = -1,
- FRAME_EXECUTING = 0,
- FRAME_RETURNED = 1,
- FRAME_UNWINDING = 2,
- FRAME_RAISED = 3,
- FRAME_CLEARED = 4
-};
-
-typedef signed char PyFrameState;
-
 struct _frame {
  PyObject_HEAD
  struct _frame *f_back; /* previous frame, or NULL */
- PyObject **f_valuestack; /* points after the last local */
+ struct _interpreter_frame *f_frame; /* points to the frame data */
  PyObject *f_trace; /* Trace function */
- /* Borrowed reference to a generator, or NULL */
- PyObject *f_gen;
- int f_stackdepth; /* Depth of value stack */
- int f_lasti; /* Last instruction if called */
  int f_lineno; /* Current line number. Only valid if non-zero */
- PyFrameState f_state; /* What state the frame is in */
  char f_trace_lines; /* Emit per-line trace events? */
  char f_trace_opcodes; /* Emit per-opcode trace events? */
  char f_own_locals_memory; /* This frame owns the memory for the locals */
- PyObject **f_localsptr; /* Pointer to locals, cells, free */
 };
 
-static inline int _PyFrame_IsRunnable(struct _frame *f) {
- return f->f_state < FRAME_EXECUTING;
-}
-
-static inline int _PyFrame_IsExecuting(struct _frame *f) {
- return f->f_state == FRAME_EXECUTING;
-}
-
-static inline int _PyFrameHasCompleted(struct _frame *f) {
- return f->f_state > FRAME_EXECUTING;
-}
-
 /* Standard object interface */
 
 PyAPI_DATA(PyTypeObject) PyFrame_Type;
@@ -59,7 +26,7 @@ PyAPI_FUNC(PyFrameObject *) PyFrame_New(PyThreadState *, PyCodeObject *,
 
 /* only internal use */
 PyFrameObject*
-_PyFrame_New_NoTrack(PyThreadState *, PyFrameConstructor *, PyObject *, PyObject **);
+_PyFrame_New_NoTrack(struct _interpreter_frame *, int);
 
 
 /* The rest of the interface is specific for frame objects */

Include/cpython/pystate.h

@@ -78,7 +78,7 @@ struct _ts {
  PyInterpreterState *interp;
 
  /* Borrowed reference to the current frame (it can be NULL) */
- PyFrameObject *frame;
+ struct _interpreter_frame *frame;
  int recursion_depth;
  int recursion_headroom; /* Allow 50 more calls to handle any errors. */
  int stackcheck_counter;
@@ -223,7 +223,7 @@ PyAPI_FUNC(void) PyThreadState_DeleteCurrent(void);
 
 /* Frame evaluation API */
 
-typedef PyObject* (*_PyFrameEvalFunction)(PyThreadState *tstate, PyFrameObject *, int);
+typedef PyObject* (*_PyFrameEvalFunction)(PyThreadState *tstate, struct _interpreter_frame *, int);
 
 PyAPI_FUNC(_PyFrameEvalFunction) _PyInterpreterState_GetEvalFrameFunc(
  PyInterpreterState *interp);

Include/genobject.h

@@ -16,9 +16,9 @@ extern "C" {
 #define _PyGenObject_HEAD(prefix) \
  PyObject_HEAD \
  /* Note: gi_frame can be NULL if the generator is "finished" */ \
- PyFrameObject *prefix##_frame;  \
+ struct _interpreter_frame *prefix##_xframe; \
  /* The code object backing the generator */ \
- PyCodeObject *prefix##_code;  \
+ PyCodeObject *prefix##_code; \
  /* List of weak reference. */ \
  PyObject *prefix##_weakreflist; \
  /* Name of the generator. */ \

Include/internal/pycore_ceval.h

@@ -41,9 +41,9 @@ extern PyObject *_PyEval_BuiltinsFromGlobals(
 
 
 static inline PyObject*
-_PyEval_EvalFrame(PyThreadState *tstate, PyFrameObject *f, int throwflag)
+_PyEval_EvalFrame(PyThreadState *tstate, struct _interpreter_frame *frame, int throwflag)
 {
- return tstate->interp->eval_frame(tstate, f, throwflag);
+ return tstate->interp->eval_frame(tstate, frame, throwflag);
 }
 
 extern PyObject *
@@ -107,6 +107,9 @@ static inline void _Py_LeaveRecursiveCall_inline(void) {
 
 #define Py_LeaveRecursiveCall() _Py_LeaveRecursiveCall_inline()
 
+struct _interpreter_frame *_PyEval_GetFrame(void);
+
+PyObject *_Py_MakeCoro(PyFrameConstructor *, struct _interpreter_frame *);
 
 #ifdef __cplusplus
 }

Include/internal/pycore_frame.h

@@ -4,41 +4,123 @@
 extern "C" {
 #endif
 
-enum {
- FRAME_SPECIALS_GLOBALS_OFFSET = 0,
- FRAME_SPECIALS_BUILTINS_OFFSET = 1,
- FRAME_SPECIALS_LOCALS_OFFSET = 2,
- FRAME_SPECIALS_CODE_OFFSET = 3,
- FRAME_SPECIALS_SIZE = 4
+/* These values are chosen so that the inline functions below all
+ * compare f_state to zero.
+ */
+enum _framestate {
+ FRAME_CREATED = -2,
+ FRAME_SUSPENDED = -1,
+ FRAME_EXECUTING = 0,
+ FRAME_RETURNED = 1,
+ FRAME_UNWINDING = 2,
+ FRAME_RAISED = 3,
+ FRAME_CLEARED = 4
 };
 
-static inline PyObject **
-_PyFrame_Specials(PyFrameObject *f) {
- return &f->f_valuestack[-FRAME_SPECIALS_SIZE];
+typedef signed char PyFrameState;
+
+typedef struct _interpreter_frame {
+ PyObject *f_globals;
+ PyObject *f_builtins;
+ PyObject *f_locals;
+ PyCodeObject *f_code;
+ PyFrameObject *frame_obj;
+ /* Borrowed reference to a generator, or NULL */
+ PyObject *generator;
+ struct _interpreter_frame *previous;
+ int f_lasti; /* Last instruction if called */
+ int stackdepth; /* Depth of value stack */
+ int nlocalsplus;
+ PyFrameState f_state; /* What state the frame is in */
+ PyObject *stack[1];
+} InterpreterFrame;
+
+static inline int _PyFrame_IsRunnable(InterpreterFrame *f) {
+ return f->f_state < FRAME_EXECUTING;
+}
+
+static inline int _PyFrame_IsExecuting(InterpreterFrame *f) {
+ return f->f_state == FRAME_EXECUTING;
 }
 
-/* Returns a *borrowed* reference. */
-static inline PyObject *
-_PyFrame_GetGlobals(PyFrameObject *f)
+static inline int _PyFrameHasCompleted(InterpreterFrame *f) {
+ return f->f_state > FRAME_EXECUTING;
+}
+
+#define FRAME_SPECIALS_SIZE ((sizeof(InterpreterFrame)-1)/sizeof(PyObject *))
+
+InterpreterFrame *
+_PyInterpreterFrame_HeapAlloc(PyFrameConstructor *con, PyObject *locals);
+
+static inline void
+_PyFrame_InitializeSpecials(
+ InterpreterFrame *frame, PyFrameConstructor *con,
+ PyObject *locals, int nlocalsplus)
 {
- return _PyFrame_Specials(f)[FRAME_SPECIALS_GLOBALS_OFFSET];
+ frame->f_code = (PyCodeObject *)Py_NewRef(con->fc_code);
+ frame->f_builtins = Py_NewRef(con->fc_builtins);
+ frame->f_globals = Py_NewRef(con->fc_globals);
+ frame->f_locals = Py_XNewRef(locals);
+ frame->nlocalsplus = nlocalsplus;
+ frame->stackdepth = 0;
+ frame->frame_obj = NULL;
+ frame->generator = NULL;
+ frame->f_lasti = -1;
+ frame->f_state = FRAME_CREATED;
 }
 
-/* Returns a *borrowed* reference. */
-static inline PyObject *
-_PyFrame_GetBuiltins(PyFrameObject *f)
+/* Gets the pointer to the locals array
+ * that precedes this frame.
+ */
+static inline PyObject**
+_PyFrame_GetLocalsArray(InterpreterFrame *frame)
 {
- return _PyFrame_Specials(f)[FRAME_SPECIALS_BUILTINS_OFFSET];
+ return ((PyObject **)frame) - frame->nlocalsplus;
 }
 
-/* Returns a *borrowed* reference. */
-static inline PyCodeObject *
-_PyFrame_GetCode(PyFrameObject *f)
+/* For use by _PyFrame_GetFrameObject
+ Do not call directly. */
+PyFrameObject *
+_PyFrame_MakeAndSetFrameObject(InterpreterFrame *frame);
+
+/* Gets the PyFrameObject for this frame, lazily
+ * creating it if necessary.
+ * Returns a borrowed referennce */
+static inline PyFrameObject *
+_PyFrame_GetFrameObject(InterpreterFrame *frame)
 {
- return (PyCodeObject *)_PyFrame_Specials(f)[FRAME_SPECIALS_CODE_OFFSET];
+ PyFrameObject *res = frame->frame_obj;
+ if (res != NULL) {
+ return res;
+ }
+ return _PyFrame_MakeAndSetFrameObject(frame);
 }
 
-int _PyFrame_TakeLocals(PyFrameObject *f);
+/* Clears all references in the frame.
+ * If take is non-zero, then the InterpreterFrame frame
+ * may be transfered to the frame object it references
+ * instead of being cleared. Either way
+ * the caller no longer owns the references
+ * in the frame.
+ * take should be set to 1 for heap allocated
+ * frames like the ones in generators and coroutines.
+ */
+int
+_PyFrame_Clear(InterpreterFrame * frame, int take);
+
+int
+_PyFrame_Traverse(InterpreterFrame *frame, visitproc visit, void *arg);
+
+int
+_PyFrame_FastToLocalsWithError(InterpreterFrame *frame);
+
+void
+_PyFrame_LocalsToFast(InterpreterFrame *frame, int clear);
+
+InterpreterFrame *_PyThreadState_PushFrame(
+ PyThreadState *tstate, PyFrameConstructor *con, PyObject *locals);
+
+void _PyThreadState_PopFrame(PyThreadState *tstate, InterpreterFrame *frame);
 
 #ifdef __cplusplus
 }

Include/internal/pycore_pystate.h

@@ -147,9 +147,6 @@ PyAPI_FUNC(int) _PyState_AddModule(
 
 PyAPI_FUNC(int) _PyOS_InterruptOccurred(PyThreadState *tstate);
 
-PyObject **_PyThreadState_PushLocals(PyThreadState *, int size);
-void _PyThreadState_PopLocals(PyThreadState *, PyObject **);
-
 #ifdef __cplusplus
 }
 #endif

Lib/test/test_faulthandler.py

@@ -56,6 +56,7 @@ def temporary_filename():
  os_helper.unlink(filename)
 
 class FaultHandlerTests(unittest.TestCase):
+
  def get_output(self, code, filename=None, fd=None):
  """
  Run the specified code in Python (in a new child process) and read the

Lib/test/test_sys.py

@@ -1275,7 +1275,7 @@ class C(object): pass
  # frame
  import inspect
  x = inspect.currentframe()
- check(x, size('4P3i4cP'))
+ check(x, size('3Pi3c'))
  # function
  def func(): pass
  check(func, size('14Pi'))

Makefile.pre.in

@@ -350,6 +350,7 @@ PYTHON_OBJS=	\
 Python/context.o \
 Python/dynamic_annotations.o \
 Python/errors.o \
+Python/frame.o \
 Python/frozenmain.o \
 Python/future.o \
 Python/getargs.o \