Skip to content

gh-140544: store pointer to interpreter state as a thread local for fast access #140573

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 9 commits into from
Oct 25, 2025
Merged

gh-140544: store pointer to interpreter state as a thread local for fast access #140573

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
9 commits
Select commit Hold shift + click to select a range
0ee4aba
use tls for interp
kumaraditya303 Oct 24, 2025
04318d0
use fast access for freelist
kumaraditya303 Oct 24, 2025
7115c75
cleanup 1
kumaraditya303 Oct 25, 2025
c6a7f91
add back assertion
kumaraditya303 Oct 25, 2025
40407f7
fix build
kumaraditya303 Oct 25, 2025
a42e973
fix globals check
kumaraditya303 Oct 25, 2025
a2b1487
📜🤖 Added by blurb_it.
blurb-it[bot] Oct 25, 2025
2b3d15a
review
kumaraditya303 Oct 25, 2025
2dc93d3
improve comment
kumaraditya303 Oct 25, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 4 additions & 3 deletions Include/internal/pycore_freelist.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -17,15 +17,16 @@ extern "C" {
static inline struct _Py_freelists *
_Py_freelists_GET(void)
{
PyThreadState *tstate = _PyThreadState_GET();
#ifdef Py_DEBUG
_Py_EnsureTstateNotNULL(tstate);
_Py_AssertHoldsTstate();
#endif

#ifdef Py_GIL_DISABLED
PyThreadState *tstate = _PyThreadState_GET();
return &((_PyThreadStateImpl*)tstate)->freelists;
#else
return &tstate->interp->object_state.freelists;
PyInterpreterState *interp = _PyInterpreterState_GET();
return &interp->object_state.freelists;
#endif
}

Expand Down
9 changes: 7 additions & 2 deletions Include/internal/pycore_pystate.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,7 @@ _Py_ThreadCanHandleSignals(PyInterpreterState *interp)

#if defined(HAVE_THREAD_LOCAL) && !defined(Py_BUILD_CORE_MODULE)
extern _Py_thread_local PyThreadState *_Py_tss_tstate;
extern _Py_thread_local PyInterpreterState *_Py_tss_interp;
#endif

#ifndef NDEBUG
Expand Down Expand Up @@ -204,11 +205,15 @@ _Py_EnsureFuncTstateNotNULL(const char *func, PyThreadState *tstate)
See also PyInterpreterState_Get()
and _PyGILState_GetInterpreterStateUnsafe(). */
static inline PyInterpreterState* _PyInterpreterState_GET(void) {
PyThreadState *tstate = _PyThreadState_GET();
#ifdef Py_DEBUG
PyThreadState *tstate = _PyThreadState_GET();
_Py_EnsureTstateNotNULL(tstate);
#endif
return tstate->interp;
#if !defined(Py_BUILD_CORE_MODULE)
Copy link
Contributor

@cdce8p cdce8p Oct 26, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should this be

#if defined(HAVE_THREAD_LOCAL) && !defined(Py_BUILD_CORE_MODULE)

instead?

When testing the current main against mypyc, I'm seeing a new error message

In file included from /.../mypy/mypyc/lib-rt/misc_ops.c:1137:
In file included from /.../cpython/Include/internal/pycore_object.h:12:
In file included from /.../cpython/Include/internal/pycore_gc.h:12:
/.../cpython/Include/internal/pycore_pystate.h:213:12: error: use of undeclared identifier '_Py_tss_interp'
    return _Py_tss_interp;
           ^
1 error generated.

Mypyc does use some of the internal headers. In particular

#define Py_BUILD_CORE
...
#include "internal/pycore_object.h"

Copy link
Contributor Author

@kumaraditya303 kumaraditya303 Oct 26, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I guess it is because mypyc doesn't define HAVE_THREAD_LOCAL which is defined when python is built, does #140623 fixes it for you?

Copy link
Member

@ZeroIntensity ZeroIntensity Oct 26, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I think we should just remove the check for HAVE_THREAD_LOCAL on line 92.

Copy link
Contributor

@cdce8p cdce8p Oct 26, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I guess it is because mypyc doesn't define HAVE_THREAD_LOCAL which is defined when python is built, does #140623 fixes it for you?

Yes, that works.

I think we should just remove the check for HAVE_THREAD_LOCAL on line 92.

Guess, this would work too.

return _Py_tss_interp;
#else
return _PyThreadState_GET()->interp;
#endif
}


Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-10-25-07-25-52.gh-issue-140544.lwjtQe.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Speed up accessing interpreter state by caching it in a thread local variable. Patch by Kumar Aditya.
12 changes: 9 additions & 3 deletions Python/pystate.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -78,6 +78,10 @@ _Py_thread_local PyThreadState *_Py_tss_tstate = NULL;
also known as a "gilstate." */
_Py_thread_local PyThreadState *_Py_tss_gilstate = NULL;

/* The interpreter of the attached thread state,
and is same as tstate->interp. */
_Py_thread_local PyInterpreterState *_Py_tss_interp = NULL;

static inline PyThreadState *
current_fast_get(void)
{
Expand All @@ -89,12 +93,15 @@ current_fast_set(_PyRuntimeState *Py_UNUSED(runtime), PyThreadState *tstate)
{
assert(tstate != NULL);
_Py_tss_tstate = tstate;
assert(tstate->interp != NULL);
_Py_tss_interp = tstate->interp;
}

static inline void
current_fast_clear(_PyRuntimeState *Py_UNUSED(runtime))
{
_Py_tss_tstate = NULL;
_Py_tss_interp = NULL;
}

#define tstate_verify_not_active(tstate) \
Expand Down Expand Up @@ -1281,9 +1288,8 @@ _PyInterpreterState_RequireIDRef(PyInterpreterState *interp, int required)
PyInterpreterState*
PyInterpreterState_Get(void)
{
PyThreadState *tstate = current_fast_get();
_Py_EnsureTstateNotNULL(tstate);
PyInterpreterState *interp = tstate->interp;
_Py_AssertHoldsTstate();
PyInterpreterState *interp = _Py_tss_interp;
if (interp == NULL) {
Py_FatalError("no current interpreter");
}
Expand Down
1 change: 1 addition & 0 deletions Tools/c-analyzer/cpython/ignored.tsv
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -194,6 +194,7 @@ Python/pyfpe.c - PyFPE_counter -
Python/import.c - pkgcontext -
Python/pystate.c - _Py_tss_tstate -
Python/pystate.c - _Py_tss_gilstate -
Python/pystate.c - _Py_tss_interp -

##-----------------------
## should be const
Expand Down
Loading