Index: Python/ceval.c
===================================================================
--- Python/ceval.c	(revision 67458)
+++ Python/ceval.c	(working copy)
@@ -504,6 +504,13 @@
 static enum why_code do_raise(PyObject *, PyObject *, PyObject *);
 static int unpack_iterable(PyObject *, int, PyObject **);
 
+/* Records whether tracing is on for any thread.  Counts the number of
+   threads for which tstate->c_tracefunc is non-NULL, so if the value
+   is 0, we know we don't have to check this thread's c_tracefunc.
+   This speeds up the if statement in PyEval_EvalFrameEx() after
+   fast_next_opcode*/
+static int _Py_TracingPossible = 0;
+
 /* for manipulating the thread switch and periodic "stuff" - used to be
    per thread, now just a pair o' globals */
 int _Py_CheckInterval = 100;
@@ -886,7 +893,8 @@
 
 		/* line-by-line tracing support */
 
-		if (tstate->c_tracefunc != NULL && !tstate->tracing) {
+		if (_Py_TracingPossible &&
+		    tstate->c_tracefunc != NULL && !tstate->tracing) {
 			/* see maybe_call_line_trace
 			   for expository comments */
 			f->f_stacktop = stack_pointer;
@@ -3414,6 +3422,9 @@
 {
 	PyThreadState *tstate = PyThreadState_GET();
 	PyObject *temp = tstate->c_traceobj;
+	int tracing_adjustment = 0;
+	if (tstate->c_tracefunc != NULL)
+		tracing_adjustment = -1;
 	Py_XINCREF(arg);
 	tstate->c_tracefunc = NULL;
 	tstate->c_traceobj = NULL;
@@ -3425,6 +3436,9 @@
 	/* Flag that tracing or profiling is turned on */
 	tstate->use_tracing = ((func != NULL)
 			       || (tstate->c_profilefunc != NULL));
+	if (func != NULL)
+		++tracing_adjustment;
+	_Py_TracingPossible += tracing_adjustment;
 }
 
 PyObject *