Prepare for parallel Disk I/O

libs/ardour/ardour/io_tasklist.h

@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2024 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef _ardour_io_tasklist_h_
+#define _ardour_io_tasklist_h_
+
+#include <boost/function.hpp>
+#include <vector>
+
+#include "ardour/libardour_visibility.h"
+
+namespace ARDOUR
+{
+
+class LIBARDOUR_API IOTaskList
+{
+public:
+	IOTaskList ();
+	~IOTaskList ();
+
+	/** process tasks in list in parallel, wait for them to complete */
+	void process ();
+	void push_back (boost::function<void ()> fn);
+
+private:
+	std::vector<boost::function<void ()>> _tasks;
+
+	size_t _n_threads;
+};
+
+} // namespace ARDOUR
+#endif

libs/ardour/ardour/session.h

@@ -149,6 +149,7 @@ struct GraphChain;
 class IO;
 class IOPlug;
 class IOProcessor;
+class IOTaskList;
 class ImportStatus;
 class MidiClockTicker;
 class MidiControlUI;
@@ -334,6 +335,7 @@ public:
 	}
 
 	std::shared_ptr<RTTaskList> rt_tasklist () { return _rt_tasklist; }
+	std::shared_ptr<IOTaskList> io_tasklist () { return _io_tasklist; }
 
 	RouteList get_routelist (bool mixer_order = false, PresentationInfo::Flag fl = PresentationInfo::MixerRoutes) const;
 
@@ -2344,6 +2346,7 @@ private:
 	std::shared_ptr<Port>  _ltc_output_port;
 
 	std::shared_ptr<RTTaskList> _rt_tasklist;
+	std::shared_ptr<IOTaskList> _io_tasklist;
 
 	/* Scene Changing */
 	SceneChanger* _scene_changer;

libs/ardour/butler.cc

@@ -44,6 +44,7 @@
 #include "ardour/disk_io.h"
 #include "ardour/disk_reader.h"
 #include "ardour/io.h"
+#include "ardour/io_tasklist.h"
 #include "ardour/session.h"
 #include "ardour/track.h"
 
@@ -264,6 +265,8 @@ Butler::thread_work ()
 
 		DEBUG_TRACE (DEBUG::Butler, string_compose ("butler starts refill loop, twr = %1\n", transport_work_requested ()));
 
+		std::shared_ptr<IOTaskList> tl = _session.io_tasklist ();
+
 		for (i = rl_with_auditioner.begin (); !transport_work_requested () && should_run && i != rl_with_auditioner.end (); ++i) {
 			std::shared_ptr<Track> tr = std::dynamic_pointer_cast<Track> (*i);
 
@@ -278,24 +281,27 @@ Butler::thread_work ()
 				// DEBUG_TRACE (DEBUG::Butler, string_compose ("butler skips inactive track %1\n", tr->name()));
 				continue;
 			}
-			// DEBUG_TRACE (DEBUG::Butler, string_compose ("butler refills %1, playback load = %2\n", tr->name(), tr->playback_buffer_load()));
-			switch (tr->do_refill ()) {
-				case 0:
-					//DEBUG_TRACE (DEBUG::Butler, string_compose ("\ttrack refill done %1\n", tr->name()));
-					break;
 
-				case 1:
-					DEBUG_TRACE (DEBUG::Butler, string_compose ("\ttrack refill unfinished %1\n", tr->name ()));
-					disk_work_outstanding = true;
-					break;
-
-				default:
-					error << string_compose (_("Butler read ahead failure on dstream %1"), (*i)->name ()) << endmsg;
-					std::cerr << string_compose (_("Butler read ahead failure on dstream %1"), (*i)->name ()) << std::endl;
-					break;
-			}
+			tl->push_back ([tr, &disk_work_outstanding]() {
+				switch (tr->do_refill ()) {
+					case 0:
+						//DEBUG_TRACE (DEBUG::Butler, string_compose ("\ttrack refill done %1\n", tr->name()));
+						break;
+					case 1:
+						DEBUG_TRACE (DEBUG::Butler, string_compose ("\ttrack refill unfinished %1\n", tr->name ()));
+						disk_work_outstanding = true;
+						break;
+					default:
+						error << string_compose (_("Butler read ahead failure on dstream %1"), tr->name ()) << endmsg;
+						std::cerr << string_compose (_("Butler read ahead failure on dstream %1"), tr->name ()) << std::endl;
+						break;
+				}
+			});
 		}
 
+		tl->process ();
+		tl.reset ();
+
 		if (i != rl_with_auditioner.begin () && i != rl_with_auditioner.end ()) {
 			/* we didn't get to all the streams */
 			disk_work_outstanding = true;

libs/ardour/io_tasklist.cc

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2017-2024 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "pbd/pthread_utils.h"
+
+#include "ardour/io_tasklist.h"
+
+using namespace ARDOUR;
+
+IOTaskList::IOTaskList ()
+	: _n_threads (0)
+{
+}
+
+IOTaskList::~IOTaskList ()
+{
+}
+
+void
+IOTaskList::push_back (boost::function<void ()> fn)
+{
+	_tasks.push_back (fn);
+}
+
+void
+IOTaskList::process ()
+{
+	assert (strcmp (pthread_name (), "butler") == 0);
+	//std::cout << "IOTaskList::process " << pthread_name () << " " << _tasks.size () << "\n";
+	if (_n_threads > 1 && _tasks.size () > 2) {
+		// TODO
+	} else {
+		for (auto const& fn : _tasks) {
+			fn ();
+		}
+	}
+	_tasks.clear ();
+}

libs/ardour/session.cc

@@ -85,6 +85,7 @@
 #include "ardour/gain_control.h"
 #include "ardour/graph.h"
 #include "ardour/io_plug.h"
+#include "ardour/io_tasklist.h"
 #include "ardour/luabindings.h"
 #include "ardour/lv2_plugin.h"
 #include "ardour/midiport_manager.h"
@@ -589,6 +590,7 @@ Session::immediately_post_engine ()
 
 	_process_graph.reset (new Graph (*this));
 	_rt_tasklist.reset (new RTTaskList (_process_graph));
+	_io_tasklist.reset (new IOTaskList ());
 
 	/* every time we reconnect, recompute worst case output latencies */
 
@@ -720,6 +722,8 @@ Session::destroy ()
 	_io_graph_chain[0].reset ();
 	_io_graph_chain[1].reset ();
 
+	_io_tasklist.reset ();
+
 	_butler->drop_references ();
 	delete _butler;
 	_butler = 0;

libs/ardour/session_transport.cc

@@ -54,6 +54,7 @@
 #include "ardour/click.h"
 #include "ardour/debug.h"
 #include "ardour/disk_reader.h"
+#include "ardour/io_tasklist.h"
 #include "ardour/location.h"
 #include "ardour/playlist.h"
 #include "ardour/profile.h"
@@ -1283,12 +1284,14 @@ Session::non_realtime_locate ()
 		tf = _transport_sample;
 		start = get_microseconds ();
 
+		std::shared_ptr<IOTaskList> tl = io_tasklist ();
 		for (auto const& i : *rl) {
 			++nt;
-			i->non_realtime_locate (tf);
-			if (sc != _seek_counter.load ()) {
-				goto restart;
-			}
+			tl->push_back ([this, i, tf, sc]() { if (sc == _seek_counter.load ()) { i->non_realtime_locate (tf); }});
+		}
+		tl->process ();
+		if (sc != _seek_counter.load ()) {
+			goto restart;
 		}
 
 		microseconds_t end = get_microseconds ();
@@ -1528,15 +1531,26 @@ Session::non_realtime_stop (bool abort, int on_entry, bool& finished, bool will_
 
 		DEBUG_TRACE (DEBUG::Transport, X_("Butler PTW: locate\n"));
 
-		for (auto const& i : *r) {
-			DEBUG_TRACE (DEBUG::Transport, string_compose ("Butler PTW: locate on %1\n", i->name()));
-			i->non_realtime_locate (_transport_sample);
+		std::shared_ptr<IOTaskList> tl = io_tasklist ();
 
-			if (on_entry != _butler->should_do_transport_work.load()) {
-				finished = false;
-				/* we will be back */
-				return;
-			}
+		std::atomic<bool> fini (finished);
+		for (auto const& i : *r) {
+			tl->push_back ([this, i, on_entry, &fini]() {
+				if (!fini.load ()) {
+					return;
+				}
+				DEBUG_TRACE (DEBUG::Transport, string_compose ("Butler PTW: locate on %1\n", i->name()));
+				i->non_realtime_locate (_transport_sample);
+				if (on_entry != _butler->should_do_transport_work.load()) {
+					fini = false;
+				}
+			});
+		}
+		tl->process ();
+		if (!fini.load ()) {
+			finished = false;
+			/* we will be back */
+			return;
 		}
 
 		VCAList v = _vca_manager->vcas ();

libs/ardour/wscript

@@ -110,6 +110,7 @@ libardour_sources = [
         'io.cc',
         'io_plug.cc',
         'io_processor.cc',
+        'io_tasklist.cc',
         'kmeterdsp.cc',
         'ladspa_plugin.cc',
         'latent.cc',