bpo-37146: Allow to configure opcode cache and fix huntleaks by presetting it to 1

Include/internal/pycore_pystate.h

@@ -60,6 +60,7 @@ struct _ceval_runtime_state {
     /* Request for checking signals. */
     _Py_atomic_int signals_pending;
     struct _gil_runtime_state gil;
+    struct int opcode_cache_minruns;
 };
 
 /* interpreter state */
@@ -312,6 +313,9 @@ PyAPI_FUNC(void) _PyInterpreterState_DeleteExceptMain(_PyRuntimeState *runtime);
 
 PyAPI_FUNC(void) _PyGILState_Reinit(_PyRuntimeState *runtime);
 
+PyAPI_FUNC(void) _PyEval_SetOpcodeCacheMinRuns(int minruns);
+PyAPI_FUNC(int) _PyEval_GetOpcodeCacheMinRuns(void);
+
 #ifdef __cplusplus
 }
 #endif

Lib/test/libregrtest/refleak.py

@@ -30,6 +30,8 @@ def dash_R(ns, test_name, test_func):
     if not hasattr(sys, 'gettotalrefcount'):
         raise Exception("Tracking reference leaks requires a debug build "
                         "of Python")
+    minruns = sys._getopcacheminruns()
+    sys._setopcacheminruns(1)
 
     # Avoid false positives due to various caches
     # filling slowly with random data:
@@ -104,6 +106,7 @@ def get_pooled_int(value):
         rc_before = rc_after
         fd_before = fd_after
 
+    sys._setopcacheminruns(minruns)
     if not ns.quiet:
         print(file=sys.stderr)
 

Lib/test/libregrtest/runtest.py

@@ -243,7 +243,6 @@ def _runtest_inner2(ns, test_name):
         gc.garbage.clear()
 
     support.reap_children()
-
     return refleak
 
 

Misc/NEWS.d/next/Core and Builtins/2019-06-03-23-29-35.bpo-37146.5B7ZiD.rst

@@ -0,0 +1,3 @@
+Added ``sys._setopcacheminruns`` and ``sys._getopcacheminruns`` to allow
+configuring the minimum number of function executions to activate the global
+opcode cache.

Python/ceval.c

@@ -103,7 +103,6 @@ static long dxp[256];
 #endif
 
 /* per opcode cache */
-#define OPCACHE_MIN_RUNS 1024  /* create opcache when code executed this time */
 #define OPCACHE_STATS 0  /* Enable stats */
 
 #if OPCACHE_STATS
@@ -1152,9 +1151,10 @@ _PyEval_EvalFrameDefault(PyFrameObject *f, int throwflag)
     f->f_stacktop = NULL;       /* remains NULL unless yield suspends frame */
     f->f_executing = 1;
 
-    if (co->co_opcache_flag < OPCACHE_MIN_RUNS) {
+    int opcacheminruns = _PyEval_GetOpcodeCacheMinRuns();
+    if (co->co_opcache_flag < opcacheminruns) {
         co->co_opcache_flag++;
-        if (co->co_opcache_flag == OPCACHE_MIN_RUNS) {
+        if (co->co_opcache_flag == opcacheminruns) {
             if (_PyCode_InitOpcache(co) < 0) {
                 return NULL;
             }
@@ -5632,3 +5632,15 @@ maybe_dtrace_line(PyFrameObject *frame,
     }
     *instr_prev = frame->f_lasti;
 }
+
+void
+_PyEval_SetOpcodeCacheMinRuns(int minruns)
+{
+    _PyRuntime.ceval.opcode_cache_minruns = minruns;
+}
+
+int
+_PyEval_GetOpcodeCacheMinRuns()
+{
+     return _PyRuntime.ceval.opcode_cache_minruns;
+}

Python/pylifecycle.c

@@ -737,6 +737,8 @@ _Py_PreInitializeFromPyArgv(const PyPreConfig *src_config, const _PyArgv *args)
         return status;
     }
 
+    runtime->ceval.opcodeconfig.minruns = 1024;
+
     runtime->pre_initialized = 1;
     return _PyStatus_OK();
 }

Python/sysmodule.c

@@ -1030,6 +1030,44 @@ sys_getcheckinterval_impl(PyObject *module)
     return PyLong_FromLong(interp->check_interval);
 }
 
+/*[clinic input]
+sys._setopcacheminruns
+
+    minruns: int
+    /
+
+Set the minimum value of runs to activate opcode cache.
+[clinic start generated code]*/
+
+static PyObject *
+sys__setopcacheminruns_impl(PyObject *module, int minruns)
+/*[clinic end generated code: output=e29d082b62b2aa8a input=169a982eee6595d5]*/
+{
+    if (minruns <= 0) {
+        PyErr_SetString(PyExc_ValueError,
+                        "opcache min runs must be strictly positive");
+        return NULL;
+    }
+    _PyEval_SetOpcodeCacheMinRuns(minruns);
+    Py_RETURN_NONE;
+}
+
+
+/*[clinic input]
+sys._getopcacheminruns -> int
+
+Return the current minimum value of runs to activate opcode cache.
+[clinic start generated code]*/
+
+static int
+sys__getopcacheminruns_impl(PyObject *module)
+/*[clinic end generated code: output=f25d23b7afd8512c input=93784822a3e883c9]*/
+{
+    return _PyEval_GetOpcodeCacheMinRuns();
+}
+
+
+
 /*[clinic input]
 sys.setswitchinterval
 
@@ -1936,6 +1974,8 @@ static PyMethodDef sys_methods[] = {
     SYS_MDEBUG_METHODDEF
     SYS_SETCHECKINTERVAL_METHODDEF
     SYS_GETCHECKINTERVAL_METHODDEF
+    SYS__SETOPCACHEMINRUNS_METHODDEF
+    SYS__GETOPCACHEMINRUNS_METHODDEF
     SYS_SETSWITCHINTERVAL_METHODDEF
     SYS_GETSWITCHINTERVAL_METHODDEF
     SYS_SETDLOPENFLAGS_METHODDEF