diff --git a/libs/ardour/ardour/graph.h b/libs/ardour/ardour/graph.h
index 0515b335ce..2ba8ae921c 100644
--- a/libs/ardour/ardour/graph.h
+++ b/libs/ardour/ardour/graph.h
@@ -59,8 +59,9 @@ public:
 
 	void trigger (GraphNode* n);
 	void rechain (boost::shared_ptr<RouteList>, GraphEdges const&);
+	bool plot (std::string const& file_name) const;
 
-	void dump (int chain);
+	void plot (int chain);
 	void reached_terminal_node ();
 
 	void helper_thread ();
@@ -84,6 +85,7 @@ private:
 	void run_one ();
 	void main_thread ();
 	void prep ();
+	void dump (int chain) const;
 
 	node_list_t _nodes_rt[2];
 	node_list_t _init_trigger_list[2];
@@ -115,8 +117,8 @@ private:
 	volatile gint _terminate;
 
 	/* chain swapping */
-	Glib::Threads::Mutex _swap_mutex;
 	Glib::Threads::Cond  _cleanup_cond;
+	mutable Glib::Threads::Mutex _swap_mutex;
 
 	volatile int _current_chain;
 	volatile int _pending_chain;
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index cfab99bcf6..81c692580a 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -328,6 +328,8 @@ public:
 	uint32_t ntracks () const;
 	uint32_t nbusses () const;
 
+	bool plot_process_graph (std::string const& file_name) const;
+
 	boost::shared_ptr<BundleList> bundles () {
 		return _bundles.reader ();
 	}
diff --git a/libs/ardour/graph.cc b/libs/ardour/graph.cc
index ef7393e824..0cf3f79101 100644
--- a/libs/ardour/graph.cc
+++ b/libs/ardour/graph.cc
@@ -526,11 +526,11 @@ again:
 }
 
 void
-Graph::dump (int chain)
+Graph::dump (int chain) const
 {
 #ifndef NDEBUG
-	node_list_t::iterator ni;
-	node_set_t::iterator  ai;
+	node_list_t::const_iterator ni;
+	node_set_t::const_iterator  ai;
 
 	chain = _pending_chain;
 
@@ -552,6 +552,56 @@ Graph::dump (int chain)
 #endif
 }
 
+bool
+Graph::plot (std::string const& file_name) const
+{
+	Glib::Threads::Mutex::Lock ls (_swap_mutex);
+	int chain = _current_chain;
+
+	node_list_t::const_iterator ni;
+	node_set_t::const_iterator  ai;
+	stringstream ss;
+
+	ss << "digraph {\n";
+	ss << "  node [shape = ellipse];\n";
+
+	for (ni = _nodes_rt[chain].begin (); ni != _nodes_rt[chain].end (); ni++) {
+		boost::shared_ptr<Route> sr = boost::dynamic_pointer_cast<Route> (*ni);
+		std::string sn = string_compose ("%1 (%2)", sr->name (), (*ni)->_init_refcount[chain]);
+		if ((*ni)->_init_refcount[chain] == 0 && (*ni)->_activation_set[chain].size() == 0) {
+				ss << "  \"" << sn << "\"[style=filled,fillcolor=gold1];\n";
+		} else if ((*ni)->_init_refcount[chain] == 0) {
+				ss << "  \"" << sn << "\"[style=filled,fillcolor=lightskyblue1];\n";
+		} else if ((*ni)->_activation_set[chain].size() == 0) {
+				ss << "  \"" << sn << "\"[style=filled,fillcolor=aquamarine2];\n";
+		}
+		for (ai = (*ni)->_activation_set[chain].begin (); ai != (*ni)->_activation_set[chain].end (); ai++) {
+			boost::shared_ptr<Route> dr = boost::dynamic_pointer_cast<Route> (*ai);
+			std::string dn = string_compose ("%1 (%2)", dr->name (), (*ai)->_init_refcount[chain]);
+			bool sends_only = false;
+			sr->feeds (dr, &sends_only);
+			if (sends_only) {
+				ss << "  edge [style=dashed];\n";
+			}
+			ss << "  \"" << sn << "\" -> \"" << dn << "\"\n";
+			if (sends_only) {
+				ss << "  edge [style=solid];\n";
+			}
+		}
+	}
+	ss << "}\n";
+
+	GError *err = NULL;
+	if (!g_file_set_contents (file_name.c_str(), ss.str().c_str(), -1, &err)) {
+		if (err) {
+			error << string_compose (_("Could not graph to file (%1)"), err->message) << endmsg;
+			g_error_free (err);
+		}
+		return false;
+	}
+	return true;
+}
+
 int
 Graph::process_routes (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool& need_butler)
 {
diff --git a/libs/ardour/luabindings.cc b/libs/ardour/luabindings.cc
index 4e04cd59a7..6fb9411a1e 100644
--- a/libs/ardour/luabindings.cc
+++ b/libs/ardour/luabindings.cc
@@ -2279,6 +2279,7 @@ LuaBindings::common (lua_State* L)
 		.addFunction ("get_tracks", &Session::get_tracks)
 		.addFunction ("get_stripables", (StripableList (Session::*)() const)&Session::get_stripables)
 		.addFunction ("get_routelist", &Session::get_routelist)
+		.addFunction ("plot_process_graph", &Session::plot_process_graph)
 
 		.addFunction ("name", &Session::name)
 		.addFunction ("path", &Session::path)
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 584c5cfb4d..71468c2a10 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -6482,6 +6482,11 @@ Session::nstripables (bool with_monitor) const
 	return rv;
 }
 
+bool
+Session::plot_process_graph (std::string const& file_name) const {
+	return _process_graph ? _process_graph->plot (file_name) : false;
+}
+
 void
 Session::add_automation_list(AutomationList *al)
 {