Remove unneeded 'mutex' member.

Include/internal/pycore_gc.h

@@ -341,6 +341,7 @@ extern int _PyGC_VisitStackRef(union _PyStackRef *ref, visitproc visit, void *ar
 #ifdef Py_GIL_DISABLED
 extern void _PyGC_VisitObjectsWorldStopped(PyInterpreterState *interp,
                                            gcvisitobjects_t callback, void *arg);
+extern Py_ssize_t _PyGC_GetMimallocAllocatedBytes(PyInterpreterState *interp);
 #endif
 
 #ifdef __cplusplus

Include/internal/pycore_interp_structs.h

@@ -268,9 +268,6 @@ struct _gc_runtime_state {
        Adjusted after each collection based on the fraction of objects found to
        be trash. */
     int adaptive_threshold;
-
-    /* Mutex held for gc_should_collect_mem_usage(). */
-    PyMutex mutex;
 #else
     PyGC_Head *generation0;
 #endif

Python/gc_free_threading.c

@@ -463,6 +463,47 @@ gc_visit_heaps(PyInterpreterState *interp, mi_block_visit_fun *visitor,
     return err;
 }
 
+// Visitor for _PyGC_GetMimallocAllocatedBytes(): called once per heap area
+// when visit_blocks=false.  Sums area->used * area->block_size.
+static bool
+mimalloc_used_area_visitor(const mi_heap_t *heap, const mi_heap_area_t *area,
+                           void *block, size_t block_size, void *arg)
+{
+    if (block == NULL) {
+        *(Py_ssize_t *)arg += (Py_ssize_t)(area->used * area->block_size);
+    }
+    return true;
+}
+
+// Return the total bytes in use across all mimalloc heaps for all threads in
+// the interpreter, plus the per-interp abandoned pool.
+Py_ssize_t
+_PyGC_GetMimallocAllocatedBytes(PyInterpreterState *interp)
+{
+    Py_ssize_t total = 0;
+    _PyEval_StopTheWorld(interp);
+    HEAD_LOCK(&_PyRuntime);
+    _Py_FOR_EACH_TSTATE_UNLOCKED(interp, p) {
+        struct _mimalloc_thread_state *m =
+            &((_PyThreadStateImpl *)p)->mimalloc;
+        if (!_Py_atomic_load_int(&m->initialized)) {
+            continue;
+        }
+        for (int h = 0; h < _Py_MIMALLOC_HEAP_COUNT; h++) {
+            mi_heap_visit_blocks(&m->heaps[h], false,
+                                 mimalloc_used_area_visitor, &total);
+        }
+    }
+    mi_abandoned_pool_t *pool = &interp->mimalloc.abandoned_pool;
+    for (uint8_t tag = 0; tag < _Py_MIMALLOC_HEAP_COUNT; tag++) {
+        _mi_abandoned_pool_visit_blocks(pool, tag, false,
+                                        mimalloc_used_area_visitor, &total);
+    }
+    HEAD_UNLOCK(&_PyRuntime);
+    _PyEval_StartTheWorld(interp);
+    return total;
+}
+
 static inline void
 gc_visit_stackref(_PyStackRef stackref)
 {

Python/sysmodule.c

@@ -19,6 +19,7 @@ Data members:
 #include "pycore_call.h"          // _PyObject_CallNoArgs()
 #include "pycore_ceval.h"         // _PyEval_SetAsyncGenFinalizer()
 #include "pycore_frame.h"         // _PyInterpreterFrame
+#include "pycore_gc.h"            // _PyGC_GetMimallocAllocatedBytes()
 #include "pycore_import.h"        // _PyImport_SetDLOpenFlags()
 #include "pycore_initconfig.h"    // _PyStatus_EXCEPTION()
 #include "pycore_interpframe.h"   // _PyFrame_GetFirstComplete()
@@ -2060,6 +2061,32 @@ sys_getallocatedblocks_impl(PyObject *module)
     return _Py_GetGlobalAllocatedBlocks();
 }
 
+PyDoc_STRVAR(sys__get_mimalloc_allocated_bytes__doc__,
+"_get_mimalloc_allocated_bytes($module, /)\n"
+"--\n"
+"\n"
+"Return total bytes allocated across all mimalloc heaps in this interpreter.\n"
+"\n"
+"Free-threaded build only.  Stops the world while reading per-thread heap\n"
+"structures.  Intended for benchmarking: the OS RSS does not reliably reflect\n"
+"Python's live memory because mimalloc retains freed pages.\n"
+"Raises NotImplementedError on the GIL-enabled build.");
+
+static PyObject *
+sys__get_mimalloc_allocated_bytes(PyObject *module, PyObject *Py_UNUSED(ignored))
+{
+#ifdef Py_GIL_DISABLED
+    PyInterpreterState *interp = _PyInterpreterState_GET();
+    Py_ssize_t total = _PyGC_GetMimallocAllocatedBytes(interp);
+    return PyLong_FromSsize_t(total);
+#else
+    PyErr_SetString(PyExc_NotImplementedError,
+                    "sys._get_mimalloc_allocated_bytes() is only available "
+                    "on the free-threaded build");
+    return NULL;
+#endif
+}
+
 /*[clinic input]
 sys.getunicodeinternedsize -> Py_ssize_t
 
@@ -2927,6 +2954,8 @@ static PyMethodDef sys_methods[] = {
     SYS_GETDEFAULTENCODING_METHODDEF
     SYS_GETDLOPENFLAGS_METHODDEF
     SYS_GETALLOCATEDBLOCKS_METHODDEF
+    {"_get_mimalloc_allocated_bytes", sys__get_mimalloc_allocated_bytes,
+     METH_NOARGS, sys__get_mimalloc_allocated_bytes__doc__},
     SYS_GETUNICODEINTERNEDSIZE_METHODDEF
     SYS_GETFILESYSTEMENCODING_METHODDEF
     SYS_GETFILESYSTEMENCODEERRORS_METHODDEF