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gh-131253: free-threaded build support for pystats #137189

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1c194e2
gh-131253: free-threaded build support for pystats
nascheme Jul 19, 2025
7dc9191
Make pystats global state be per-interpreter.
nascheme Jul 30, 2025
60454a2
Add NEWS.
nascheme Jul 30, 2025
df1c5d4
Merge 'origin/main' into gh-131253-pystats-ft
nascheme Jul 30, 2025
c94e5c4
Fix some data race issues.
nascheme Jul 31, 2025
e77af2c
Remove _Py_tss_stats thread local.
nascheme Aug 6, 2025
488f0be
Merge 'origin/main' into gh-131253-pystats-ft
nascheme Aug 6, 2025
a48c7f6
Improve _Py_STATS_COND_EXPR macro.
nascheme Aug 7, 2025
612ea96
Improve comment for ts->pystats member.
nascheme Aug 7, 2025
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Remove _Py_tss_stats thread local. 
Add pystats pointer to PyThreadState and use from there instead.  This
is slightly slower but shouldn't matter in practice.  This simplifies
the attach/detach logic as well.
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@nascheme
nascheme committed Aug 6, 2025
commit e77af2c703999ee20ebffa8380931a806a10e9d0
19 changes: 19 additions & 0 deletions Include/cpython/pystate.h
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Expand Up @@ -208,6 +208,10 @@ struct _ts {
*/
PyObject *threading_local_sentinel;
_PyRemoteDebuggerSupport remote_debugger_support;

#ifdef Py_STATS
PyStats *pystats; // pointer PyStats structure, NULL if recording is off
#endif
};

/* other API */
Expand All @@ -230,6 +234,21 @@ PyAPI_FUNC(void) PyThreadState_EnterTracing(PyThreadState *tstate);
// function is set, otherwise disable them.
PyAPI_FUNC(void) PyThreadState_LeaveTracing(PyThreadState *tstate);

#ifdef Py_STATS
#if defined(HAVE_THREAD_LOCAL) && !defined(Py_BUILD_CORE_MODULE)
extern _Py_thread_local PyThreadState* _Py_tss_tstate;

static inline PyStats*
_PyThreadState_GetStatsFast(void)
{
if (_Py_tss_tstate == NULL) {
return NULL; // no attached thread state
}
return _Py_tss_tstate->pystats;
}
#endif
#endif // Py_STATS

/* PyGILState */

/* Helper/diagnostic function - return 1 if the current thread
Expand Down
24 changes: 9 additions & 15 deletions Include/cpython/pystats.h
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Expand Up @@ -14,7 +14,7 @@
// - sys._stats_dump()
//
// Python must be built with ./configure --enable-pystats to define the
// _PyStats_GET() function.
// _PyStats_GET() macro.
//
// Define _PY_INTERPRETER macro to increment interpreter_increfs and
// interpreter_decrefs. Otherwise, increment increfs and decrefs.
Expand Down Expand Up @@ -112,8 +112,11 @@ typedef struct _gc_stats {
#ifdef Py_GIL_DISABLED
// stats specific to free-threaded build
typedef struct _ft_stats {
// number of times interpreter had to spin or park when trying to acquire a mutex
uint64_t mutex_sleeps;
// number of times that the QSBR mechanism polled (compute read sequence value)
uint64_t qsbr_polls;
// number of times stop-the-world mechanism was used
uint64_t world_stops;
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@kumaraditya303 kumaraditya303 Aug 13, 2025 •
edited
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It would be useful to have the total duration of stop-the-world pause too

} FTStats;
#endif
Expand Down Expand Up @@ -189,25 +192,16 @@ typedef struct _stats {
GCStats gc_stats[3]; // must match NUM_GENERATIONS
} PyStats;


#if defined(HAVE_THREAD_LOCAL) && !defined(Py_BUILD_CORE_MODULE)
extern _Py_thread_local PyStats *_Py_tss_stats;
#endif

// Export for most shared extensions, used via _PyStats_GET() static
// inline function.
// Export for most shared extensions
PyAPI_FUNC(PyStats *) _PyStats_GetLocal(void);

// Return pointer to the PyStats structure, NULL if recording is off.
static inline PyStats*
_PyStats_GET(void)
{
#if defined(HAVE_THREAD_LOCAL) && !defined(Py_BUILD_CORE_MODULE)
return _Py_tss_stats;
// use inline function version defined in cpython/pystate.h
static inline PyStats* _PyThreadState_GetStatsFast(void);
#define _PyStats_GET _PyThreadState_GetStatsFast
#else
return _PyStats_GetLocal();
#define _PyStats_GET _PyStats_GetLocal
#endif
}

#define _Py_STATS_EXPR(expr) \
do { \
Expand Down
11 changes: 4 additions & 7 deletions Include/internal/pycore_tstate.h
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Expand Up @@ -71,16 +71,13 @@ typedef struct _PyThreadStateImpl {
// When >1, code objects do not immortalize their non-string constants.
int suppress_co_const_immortalization;

#endif // Py_GIL_DISABLED

#ifdef Py_STATS
#ifdef Py_GIL_DISABLED
// per-thread stats, will be merged into interp->pystats_struct
PyStats *pystats_struct; // allocated by _PyStats_ThreadInit()
#endif
PyStats **pystats_tss; // pointer to tss variable
// per-thread stats, will be merged into interp->pystats_struct
PyStats *pystats_struct; // allocated by _PyStats_ThreadInit()
#endif

#endif // Py_GIL_DISABLED

#if defined(Py_REF_DEBUG) && defined(Py_GIL_DISABLED)
Py_ssize_t reftotal; // this thread's total refcount operations
#endif
Expand Down
35 changes: 16 additions & 19 deletions Python/pystats.c
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Expand Up @@ -3,6 +3,7 @@
#include "pycore_opcode_metadata.h" // _PyOpcode_Caches
#include "pycore_pyatomic_ft_wrappers.h"
#include "pycore_pylifecycle.h" // _PyOS_URandomNonblock()
#include "pycore_tstate.h"
#include "pycore_uop_metadata.h" // _PyOpcode_uop_name
#include "pycore_uop_ids.h" // MAX_UOP_ID
#include "pycore_pystate.h" // _PyThreadState_GET()
Expand All @@ -12,13 +13,14 @@

#ifdef Py_STATS

// Pointer to Thread-local stats structure, null if recording is off.
_Py_thread_local PyStats *_Py_tss_stats;

PyStats *
_PyStats_GetLocal(void)
{
return _Py_tss_stats;
PyThreadState *tstate = _PyThreadState_GET();
if (tstate) {
return tstate->pystats;
}
return NULL;
}

#ifdef Py_GIL_DISABLED
Expand Down Expand Up @@ -582,20 +584,18 @@ stats_toggle_on_off(PyThreadState *tstate, int on)
if (!ts->_status.active) {
continue;
}
_PyThreadStateImpl *ts_impl = (_PyThreadStateImpl *)ts;
PyStats *s;
if (interp->pystats_enabled) {
#ifdef Py_GIL_DISABLED
s = ts_impl->pystats_struct;
s = ((_PyThreadStateImpl *)ts)->pystats_struct;
#else
s = ((PyThreadState *)tstate)->interp->pystats_struct;
#endif
}
else {
s = NULL;
}
// write to the tss variable for the 'ts' thread
*ts_impl->pystats_tss = s;
ts->pystats = s;
}
_PyEval_StartTheWorld(interp);
return 0;
Expand Down Expand Up @@ -759,31 +759,28 @@ _PyStats_ThreadFini(_PyThreadStateImpl *tstate)
}

void
_PyStats_Attach(_PyThreadStateImpl *tstate)
_PyStats_Attach(_PyThreadStateImpl *tstate_impl)
{
PyStats *s;
PyInterpreterState *interp = ((PyThreadState *)tstate)->interp;
PyThreadState *tstate = (PyThreadState *)tstate_impl;
PyInterpreterState *interp = tstate->interp;
if (FT_ATOMIC_LOAD_INT_RELAXED(interp->pystats_enabled)) {
#ifdef Py_GIL_DISABLED
s = tstate->pystats_struct;
s = ((_PyThreadStateImpl *)tstate)->pystats_struct;
#else
s = ((PyThreadState *)tstate)->interp->pystats_struct;
s = tstate->interp->pystats_struct;
#endif
}
else {
s = NULL;
}
// use correct TSS variable for thread
tstate->pystats_tss = &_Py_tss_stats;
// write to the tss variable for the 'ts' thread
_Py_tss_stats = s;
tstate->pystats = s;
}

void
_PyStats_Detach(_PyThreadStateImpl *tstate)
_PyStats_Detach(_PyThreadStateImpl *tstate_impl)
{
tstate->pystats_tss = NULL;
_Py_tss_stats = NULL;
((PyThreadState *)tstate_impl)->pystats = NULL;
}

#endif // Py_STATS
1 change: 0 additions & 1 deletion Tools/c-analyzer/cpython/ignored.tsv
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Expand Up @@ -194,7 +194,6 @@ Python/pyfpe.c - PyFPE_counter -
Python/import.c - pkgcontext -
Python/pystate.c - _Py_tss_tstate -
Python/pystate.c - _Py_tss_gilstate -
Python/pystats.c - _Py_tss_stats -

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