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bpo-45953: Statically allocate the main interpreter (and initial thread state). (gh-29883)

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Previously, the main interpreter was allocated on the heap during runtime initialization.  Here we instead embed it into _PyRuntimeState, which means it is statically allocated as part of the _PyRuntime global.  The same goes for the initial thread state (of each interpreter, including the main one).  Consequently there are fewer allocations during runtime/interpreter init, fewer possible failures, and better memory locality.

FYI, this also helps efforts to consolidate globals, which in turns helps work on subinterpreter isolation.

https://bugs.python.org/issue45953
This commit is contained in:
Eric Snow 2022-01-12 16:28:46 -07:00 • committed by GitHub
parent 0bbf30e2b9
commit ed57b36c32
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GPG key ID: 4AEE18F83AFDEB23
8 changed files with 115 additions and 34 deletions
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49
Python/pystate.c
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@ -46,6 +46,10 @@ static PyThreadState *_PyGILState_GetThisThreadState(struct _gilstate_runtime_st
static void _PyThreadState_Delete(PyThreadState *tstate, int check_current);
/* We use "initial" if the runtime gets re-used
(e.g. Py_Finalize() followed by Py_Initialize(). */
static const _PyRuntimeState initial = _PyRuntimeState_INIT;
static int
alloc_for_runtime(PyThread_type_lock *plock1, PyThread_type_lock *plock2,
PyThread_type_lock *plock3)
@ -91,9 +95,12 @@ init_runtime(_PyRuntimeState *runtime,
PyThread_type_lock xidregistry_mutex)
{
if (runtime->_initialized) {
_PyRuntimeState_reset(runtime);
assert(!runtime->initialized);
Py_FatalError("runtime already initialized");
}
assert(!runtime->preinitializing &&
!runtime->preinitialized &&
!runtime->core_initialized &&
!runtime->initialized);
runtime->open_code_hook = open_code_hook;
runtime->open_code_userdata = open_code_userdata;
@ -144,6 +151,11 @@ _PyRuntimeState_Init(_PyRuntimeState *runtime)
return _PyStatus_NO_MEMORY();
}
if (runtime->_initialized) {
// Py_Initialize() must be running again.
// Reset to _PyRuntimeState_INIT.
memcpy(runtime, &initial, sizeof(*runtime));
}
init_runtime(runtime, open_code_hook, open_code_userdata, audit_hook_head,
unicode_next_index, lock1, lock2, lock3);
@ -250,13 +262,15 @@ alloc_interpreter(void)
static void
free_interpreter(PyInterpreterState *interp)
{
PyMem_RawFree(interp);
if (!interp->_static) {
PyMem_RawFree(interp);
}
}
/* Get the interpreter state to a minimal consistent state.
Further init happens in pylifecycle.c before it can be used.
All fields not initialized here are expected to be zeroed out,
e.g. by PyMem_RawCalloc() or memset().
e.g. by PyMem_RawCalloc() or memset(), or otherwise pre-initialized.
The runtime state is not manipulated. Instead it is assumed that
the interpreter is getting added to the runtime.
*/
@ -338,23 +352,23 @@ PyInterpreterState_New(void)
assert(interpreters->main == NULL);
assert(id == 0);
interp = alloc_interpreter();
if (interp == NULL) {
goto error;
}
interp = &runtime->_main_interpreter;
assert(interp->id == 0);
assert(interp->next == NULL);
interpreters->main = interp;
}
else {
assert(id != 0);
assert(interpreters->main != NULL);
assert(id != 0);
interp = alloc_interpreter();
if (interp == NULL) {
goto error;
}
// Set to _PyInterpreterState_INIT.
memcpy(interp, &initial._main_interpreter,
sizeof(*interp));
if (id < 0) {
/* overflow or Py_Initialize() not called yet! */
@ -735,13 +749,15 @@ alloc_threadstate(void)
static void
free_threadstate(PyThreadState *tstate)
{
PyMem_RawFree(tstate);
if (!tstate->_static) {
PyMem_RawFree(tstate);
}
}
/* Get the thread state to a minimal consistent state.
Further init happens in pylifecycle.c before it can be used.
All fields not initialized here are expected to be zeroed out,
e.g. by PyMem_RawCalloc() or memset().
e.g. by PyMem_RawCalloc() or memset(), or otherwise pre-initialized.
The interpreter state is not manipulated. Instead it is assumed that
the thread is getting added to the interpreter.
*/
@ -808,10 +824,7 @@ new_threadstate(PyInterpreterState *interp)
// It's the interpreter's initial thread state.
assert(id == 1);
tstate = alloc_threadstate();
if (tstate == NULL) {
goto error;
}
tstate = &interp->_initial_thread;
}
else {
// Every valid interpreter must have at least one thread.
@ -822,6 +835,10 @@ new_threadstate(PyInterpreterState *interp)
if (tstate == NULL) {
goto error;
}
// Set to _PyThreadState_INIT.
memcpy(tstate,
&initial._main_interpreter._initial_thread,
sizeof(*tstate));
}
interp->threads.head = tstate;
@ -1159,7 +1176,7 @@ _PyThreadState_DeleteExcept(_PyRuntimeState *runtime, PyThreadState *tstate)
for (p = list; p; p = next) {
next = p->next;
PyThreadState_Clear(p);
PyMem_RawFree(p);
free_threadstate(p);
}
}