From e90e31d68247148b828763f82994831d8b12871f Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Mon, 29 Apr 2024 21:00:27 +0200
Subject: [PATCH 01/13] Add a Tracks/Waveform icon

---
 libs/widgets/ardour_icon.cc        | 36 ++++++++++++++++++++++++++++++
 libs/widgets/widgets/ardour_icon.h |  1 +
 2 files changed, 37 insertions(+)

diff --git a/libs/widgets/ardour_icon.cc b/libs/widgets/ardour_icon.cc
index 1e51999293..441cbedd0e 100644
--- a/libs/widgets/ardour_icon.cc
+++ b/libs/widgets/ardour_icon.cc
@@ -1509,6 +1509,39 @@ icon_meters (cairo_t* cr, const int width, const int height, const uint32_t fg_c
 	VECTORICONSTROKE (lw, fg_color);
 }
 
+static void
+icon_waveform (cairo_t* cr, const int width, const int height, const uint32_t fg_color)
+{
+	const double x  = width * .5;
+	const double y  = height * .5;
+	const double wh = std::min (x, y);
+
+	const double lw = DEFAULT_LINE_WIDTH;
+	const double lc = fmod (lw * .5, 1.0);
+
+	const int m = floor (1.6 * wh - lw);
+	const double x0 = rint (x + 1 - 0.5 * m);
+
+	// for i=0,60 do print (string.format ("%.2f, ", (math.random(1,100)/100) * (math.random(1,100)/100))) end
+	static const float wave[] = {
+		0.12, 0.40, 0.28, 0.21, 0.25, 0.57, 0.57, 0.41, 0.33, 0.63,
+		0.11, 0.89, 0.13, 0.29, 0.18, 0.24, 0.10, 0.05, 0.24, 0.15,
+		0.01, 0.39, 0.93, 0.27, 0.28, 0.07, 0.15, 0.12, 0.10, 0.13,
+		0.08, 0.03, 0.04, 0.59, 0.64, 0.49, 0.01, 0.04, 0.01, 0.39,
+		0.44, 0.01, 0.21, 0.12, 0.06, 0.07, 0.01, 0.11, 0.07, 0.33,
+		0.38, 0.24, 0.16, 0.64, 0.17, 0.05, 0.24, 0.07, 0.04, 0.35,
+	};
+
+	static const int p = sizeof(wave)/sizeof (float);
+
+	for (int i = 0; i < m; ++i) {
+		double dy = (wh * .8) * wave[i % p] * sqrt(sin (M_PI * i / m));
+		cairo_move_to (cr, x0 + i - lc, y - dy);
+		cairo_line_to (cr, x0 + i - lc, y + dy);
+	}
+	VECTORICONSTROKE (lw, fg_color);
+}
+
 /*****************************************************************************/
 
 bool
@@ -1667,6 +1700,9 @@ ArdourWidgets::ArdourIcon::render (cairo_t*                                   cr
 		case Meters:
 			icon_meters (cr, width, height, fg_color);
 			break;
+		case TrackWaveform:
+			icon_waveform (cr, width, height, fg_color);
+			break;
 		case NoIcon:
 			rv = false;
 			break;
diff --git a/libs/widgets/widgets/ardour_icon.h b/libs/widgets/widgets/ardour_icon.h
index 4651ec7a77..7a04c4593c 100644
--- a/libs/widgets/widgets/ardour_icon.h
+++ b/libs/widgets/widgets/ardour_icon.h
@@ -76,6 +76,7 @@ namespace ArdourWidgets { namespace ArdourIcon {
 		Lock,
 		Mixer,
 		Meters,
+		TrackWaveform,
 		NoIcon //< Last
 	};
 

From 2af2df351655096832d7aac1f12cf8c16230161c Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Mon, 29 Apr 2024 21:46:06 +0200
Subject: [PATCH 02/13] Raise the butler's I/O priority

This likely won't make much difference on modern systems,
since it requires a kernel based I/O scheduler. which is
disabled (set to "none" for NVMe and SSDs).
---
 libs/ardour/butler.cc | 11 +++++++++++
 libs/ardour/wscript   | 12 +++++++++++-
 wscript               |  1 +
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/libs/ardour/butler.cc b/libs/ardour/butler.cc
index b1e05bb344..0c16425022 100644
--- a/libs/ardour/butler.cc
+++ b/libs/ardour/butler.cc
@@ -24,6 +24,10 @@
 #include <fcntl.h>
 #include <unistd.h>
 
+#ifdef HAVE_IOPRIO
+#include <sys/syscall.h>
+#endif
+
 #ifndef PLATFORM_WINDOWS
 #include <poll.h>
 #endif
@@ -177,6 +181,13 @@ Butler::thread_work ()
 	bool                disk_work_outstanding = false;
 	RouteList::iterator i;
 
+#ifdef HAVE_IOPRIO
+	// ioprio_set (IOPRIO_WHO_PROCESS, 0 /*calling thread*/, IOPRIO_PRIO_VALUE (IOPRIO_CLASS_RT, 4))
+	if (0 != syscall (SYS_ioprio_set, 1, 0, (1 << 13) | 4)) {
+		warning << _("Cannot set I/O Priority for disk read/write thread") << endmsg;
+	}
+#endif
+
 	while (true) {
 		DEBUG_TRACE (DEBUG::Butler, string_compose ("%1 butler main loop, disk work outstanding ? %2 @ %3\n", DEBUG_THREAD_SELF, disk_work_outstanding, g_get_monotonic_time ()));
 
diff --git a/libs/ardour/wscript b/libs/ardour/wscript
index 9f87f689cb..aa75d4a256 100644
--- a/libs/ardour/wscript
+++ b/libs/ardour/wscript
@@ -345,9 +345,19 @@ def configure(conf):
 
     conf.check(header_name='sys/vfs.h', define_name='HAVE_SYS_VFS_H',mandatory=False)
     conf.check(header_name='sys/statvfs.h', define_name='HAVE_SYS_STATVFS_H',mandatory=False)
-
     conf.check(header_name='unistd.h', define_name='HAVE_UNISTD',mandatory=False)
 
+    have_sys_ioprio = conf.check_cc(
+            msg="Checking for 'ioprio_set' syscall support",
+            features  = 'c',
+            mandatory = False,
+            execute   = False,
+            fragment = "#include <sys/syscall.h>\nint main () { syscall(SYS_ioprio_set, 1, 0, 8192); return 0; }")
+
+    if have_sys_ioprio:
+            conf.define('HAVE_IOPRIO', 1)
+            conf.env['HAVE_IOPRIO'] = True
+
     conf.write_config_header('libardour-config.h', remove=False)
 
     # Boost headers
diff --git a/wscript b/wscript
index f46c3de520..a11924f964 100644
--- a/wscript
+++ b/wscript
@@ -1571,6 +1571,7 @@ const char* const ardour_config_info = "\\n\\
     write_config_text('Futex Semaphore',       conf.is_defined('USE_FUTEX_SEMAPHORE'))
     write_config_text('Freedesktop files',     opts.freedesktop)
     write_config_text('G_ENABLE_DEBUG',        opts.gdebug or conf.env['DEBUG'])
+    write_config_text('I/O Priorty Set',       conf.is_defined('HAVE_IOPRIO'))
     write_config_text('Libjack linking',       conf.env['libjack_link'])
     write_config_text('Libjack metadata',      conf.is_defined ('HAVE_JACK_METADATA'))
     write_config_text('Lua Binding Doc',       conf.is_defined('LUABINDINGDOC'))

From 170b9150381a13ccee28517aff19c61db8a8386a Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 30 Apr 2024 00:01:32 +0200
Subject: [PATCH 03/13] Prepare for parallel Disk I/O

---
 libs/ardour/ardour/io_tasklist.h | 47 ++++++++++++++++++++++++++++
 libs/ardour/ardour/session.h     |  3 ++
 libs/ardour/butler.cc            | 36 +++++++++++++---------
 libs/ardour/io_tasklist.cc       | 53 ++++++++++++++++++++++++++++++++
 libs/ardour/session.cc           |  4 +++
 libs/ardour/session_transport.cc | 38 +++++++++++++++--------
 libs/ardour/wscript              |  1 +
 7 files changed, 155 insertions(+), 27 deletions(-)
 create mode 100644 libs/ardour/ardour/io_tasklist.h
 create mode 100644 libs/ardour/io_tasklist.cc

diff --git a/libs/ardour/ardour/io_tasklist.h b/libs/ardour/ardour/io_tasklist.h
new file mode 100644
index 0000000000..daac29fdb0
--- /dev/null
+++ b/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
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index 09ef6f25d9..bfddd4c6a6 100644
--- a/libs/ardour/ardour/session.h
+++ b/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;
diff --git a/libs/ardour/butler.cc b/libs/ardour/butler.cc
index 0c16425022..8c76c9b084 100644
--- a/libs/ardour/butler.cc
+++ b/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;
diff --git a/libs/ardour/io_tasklist.cc b/libs/ardour/io_tasklist.cc
new file mode 100644
index 0000000000..8af4a7f4e2
--- /dev/null
+++ b/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 ();
+}
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index fa071ba7f3..af1438cbcf 100644
--- a/libs/ardour/session.cc
+++ b/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;
diff --git a/libs/ardour/session_transport.cc b/libs/ardour/session_transport.cc
index aeece88079..09e957983e 100644
--- a/libs/ardour/session_transport.cc
+++ b/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 ();
diff --git a/libs/ardour/wscript b/libs/ardour/wscript
index aa75d4a256..777a0325f1 100644
--- a/libs/ardour/wscript
+++ b/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',

From ee87b068e8847331a48a5e481fd973abde2660f3 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 30 Apr 2024 01:54:33 +0200
Subject: [PATCH 04/13] Move RegionFx ThreadBuffers to Butler thread

---
 libs/ardour/audioregion.cc | 5 -----
 libs/ardour/butler.cc      | 7 ++++++-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/libs/ardour/audioregion.cc b/libs/ardour/audioregion.cc
index f172143547..6944e05bca 100644
--- a/libs/ardour/audioregion.cc
+++ b/libs/ardour/audioregion.cc
@@ -2430,9 +2430,6 @@ AudioRegion::apply_region_fx (BufferSet& bufs, samplepos_t start_sample, samplep
 		}
 	}
 
-	ARDOUR::ProcessThread* pt = new ProcessThread (); // TODO -> move to butler ?
-	pt->get_buffers ();
-
 	samplecnt_t latency_offset = 0;
 
 	for (auto const& rfx : _plugins) {
@@ -2470,6 +2467,4 @@ AudioRegion::apply_region_fx (BufferSet& bufs, samplepos_t start_sample, samplep
 	}
 	_fx_pos = end_sample;
 	_fx_latent_read = false;
-	pt->drop_buffers ();
-	delete pt;
 }
diff --git a/libs/ardour/butler.cc b/libs/ardour/butler.cc
index 8c76c9b084..039d1aef00 100644
--- a/libs/ardour/butler.cc
+++ b/libs/ardour/butler.cc
@@ -172,7 +172,12 @@ Butler::_thread_work (void* arg)
 {
 	SessionEvent::create_per_thread_pool ("butler events", 4096);
 	pthread_set_name (X_("butler"));
-	return ((Butler*)arg)->thread_work ();
+	ARDOUR::ProcessThread* pt = new ProcessThread ();
+	pt->get_buffers ();
+	void* rv = ((Butler*)arg)->thread_work ();
+	pt->drop_buffers ();
+	delete pt;
+	return rv;
 }
 
 void*

From 4b0da72bc27ea5b34f82013755d3f752b99f74df Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 30 Apr 2024 01:55:12 +0200
Subject: [PATCH 05/13] Delegate all DiskReader I/O to the IOTaskList (amend
 170b9150)

---
 libs/ardour/session_transport.cc | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/libs/ardour/session_transport.cc b/libs/ardour/session_transport.cc
index 09e957983e..2f5ac62651 100644
--- a/libs/ardour/session_transport.cc
+++ b/libs/ardour/session_transport.cc
@@ -1152,14 +1152,17 @@ Session::butler_transport_work (bool have_process_lock)
 		if (!have_process_lock) {
 			lx.acquire ();
 		}
+		std::shared_ptr<IOTaskList> tl = io_tasklist ();
 		for (auto const& i : *r) {
 			std::shared_ptr<Track> tr = std::dynamic_pointer_cast<Track> (i);
 			if (tr) {
 				tr->adjust_playback_buffering ();
 				/* and refill those buffers ... */
 			}
-			i->non_realtime_locate (_transport_sample);
+			tl->push_back ([this, i]() { i->non_realtime_locate (_transport_sample); });
 		}
+		tl->process ();
+
 		VCAList v = _vca_manager->vcas ();
 		for (VCAList::const_iterator i = v.begin(); i != v.end(); ++i) {
 			(*i)->non_realtime_locate (_transport_sample);

From 5b9e4fff634e1d5052cf78375f1387bfceca4cbd Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 30 Apr 2024 03:46:39 +0200
Subject: [PATCH 06/13] Parallelize Disk I/O and RegionFx processing

---
 libs/ardour/ardour/debug.h                 |   1 +
 libs/ardour/ardour/disk_reader.h           |   6 +-
 libs/ardour/ardour/io_tasklist.h           |  18 ++-
 libs/ardour/ardour/rc_configuration_vars.h |   1 +
 libs/ardour/ardour/utils.h                 |   1 +
 libs/ardour/butler.cc                      |   5 +
 libs/ardour/debug.cc                       |   1 +
 libs/ardour/disk_reader.cc                 |   6 +-
 libs/ardour/globals.cc                     |   9 +-
 libs/ardour/io_tasklist.cc                 | 126 ++++++++++++++++++++-
 libs/ardour/session.cc                     |   5 +-
 libs/ardour/session_state.cc               |   1 -
 libs/ardour/utils.cc                       |  19 ++++
 libs/pbd/pbd/pthread_utils.h               |   3 +-
 libs/pbd/pthread_utils.cc                  |   7 ++
 15 files changed, 189 insertions(+), 20 deletions(-)

diff --git a/libs/ardour/ardour/debug.h b/libs/ardour/ardour/debug.h
index db63e17756..18aaa74ae7 100644
--- a/libs/ardour/ardour/debug.h
+++ b/libs/ardour/ardour/debug.h
@@ -58,6 +58,7 @@ namespace PBD {
 		LIBARDOUR_API extern DebugBits FaderPort;
 		LIBARDOUR_API extern DebugBits GenericMidi;
 		LIBARDOUR_API extern DebugBits Graph;
+		LIBARDOUR_API extern DebugBits IOTaskList;
 		LIBARDOUR_API extern DebugBits LTC;
 		LIBARDOUR_API extern DebugBits LV2;
 		LIBARDOUR_API extern DebugBits LV2Automate;
diff --git a/libs/ardour/ardour/disk_reader.h b/libs/ardour/ardour/disk_reader.h
index ed240c744a..63797e8685 100644
--- a/libs/ardour/ardour/disk_reader.h
+++ b/libs/ardour/ardour/disk_reader.h
@@ -229,9 +229,9 @@ private:
 	                        int                channel,
 	                        bool               reversed);
 
-	static Sample* _sum_buffer;
-	static Sample* _mixdown_buffer;
-	static gain_t* _gain_buffer;
+	static thread_local Sample* _sum_buffer;
+	static thread_local Sample* _mixdown_buffer;
+	static thread_local gain_t* _gain_buffer;
 
 	int refill (Sample* sum_buffer, Sample* mixdown_buffer, float* gain_buffer, samplecnt_t fill_level, bool reversed);
 	int refill_audio (Sample* sum_buffer, Sample* mixdown_buffer, float* gain_buffer, samplecnt_t fill_level, bool reversed);
diff --git a/libs/ardour/ardour/io_tasklist.h b/libs/ardour/ardour/io_tasklist.h
index daac29fdb0..7758b6c340 100644
--- a/libs/ardour/ardour/io_tasklist.h
+++ b/libs/ardour/ardour/io_tasklist.h
@@ -19,8 +19,12 @@
 #ifndef _ardour_io_tasklist_h_
 #define _ardour_io_tasklist_h_
 
+#include <atomic>
 #include <boost/function.hpp>
 #include <vector>
+#include <glibmm/threads.h>
+
+#include "pbd/semutils.h"
 
 #include "ardour/libardour_visibility.h"
 
@@ -30,7 +34,7 @@ namespace ARDOUR
 class LIBARDOUR_API IOTaskList
 {
 public:
-	IOTaskList ();
+	IOTaskList (uint32_t);
 	~IOTaskList ();
 
 	/** process tasks in list in parallel, wait for them to complete */
@@ -38,9 +42,19 @@ public:
 	void push_back (boost::function<void ()> fn);
 
 private:
+	static void* _worker_thread (void*);
+
+	void io_thread ();
+
 	std::vector<boost::function<void ()>> _tasks;
 
-	size_t _n_threads;
+	uint32_t               _n_threads;
+	std::atomic<uint32_t>  _n_workers;
+	std::vector<pthread_t> _workers;
+	std::atomic <bool>     _terminate;
+	PBD::Semaphore         _exec_sem;
+	PBD::Semaphore         _idle_sem;
+	Glib::Threads::Mutex   _tasks_mutex;
 };
 
 } // namespace ARDOUR
diff --git a/libs/ardour/ardour/rc_configuration_vars.h b/libs/ardour/ardour/rc_configuration_vars.h
index d6f35e1807..9b3d4f6809 100644
--- a/libs/ardour/ardour/rc_configuration_vars.h
+++ b/libs/ardour/ardour/rc_configuration_vars.h
@@ -221,6 +221,7 @@ CONFIG_VARIABLE (std::string, sample_lib_path, "sample-lib-path", "") /* custom
 CONFIG_VARIABLE (bool, allow_special_bus_removal, "allow-special-bus-removal", false)
 CONFIG_VARIABLE (int32_t, processor_usage, "processor-usage", -1)
 CONFIG_VARIABLE (int32_t, cpu_dma_latency, "cpu-dma-latency", -1) /* >=0 to enable */
+CONFIG_VARIABLE (int32_t, io_thread_count, "io-thread-count", -2)
 CONFIG_VARIABLE (gain_t, max_gain, "max-gain", 2.0) /* +6.0dB */
 CONFIG_VARIABLE (uint32_t, max_recent_sessions, "max-recent-sessions", 10)
 CONFIG_VARIABLE (uint32_t, max_recent_templates, "max-recent-templates", 10)
diff --git a/libs/ardour/ardour/utils.h b/libs/ardour/ardour/utils.h
index 0030ddead8..22a99c758f 100644
--- a/libs/ardour/ardour/utils.h
+++ b/libs/ardour/ardour/utils.h
@@ -109,6 +109,7 @@ LIBARDOUR_API const char* native_header_format_extension (ARDOUR::HeaderFormat,
 LIBARDOUR_API bool matching_unsuffixed_filename_exists_in (const std::string& dir, const std::string& name);
 
 LIBARDOUR_API uint32_t how_many_dsp_threads ();
+LIBARDOUR_API uint32_t how_many_io_threads ();
 
 LIBARDOUR_API std::string compute_sha1_of_file (std::string path);
 
diff --git a/libs/ardour/butler.cc b/libs/ardour/butler.cc
index 039d1aef00..6c954e63b4 100644
--- a/libs/ardour/butler.cc
+++ b/libs/ardour/butler.cc
@@ -172,9 +172,14 @@ Butler::_thread_work (void* arg)
 {
 	SessionEvent::create_per_thread_pool ("butler events", 4096);
 	pthread_set_name (X_("butler"));
+	/* get thread buffers for RegionFx */
 	ARDOUR::ProcessThread* pt = new ProcessThread ();
 	pt->get_buffers ();
+	DiskReader::allocate_working_buffers ();
+
 	void* rv = ((Butler*)arg)->thread_work ();
+
+	DiskReader::free_working_buffers ();
 	pt->drop_buffers ();
 	delete pt;
 	return rv;
diff --git a/libs/ardour/debug.cc b/libs/ardour/debug.cc
index e061c2840d..99a8dbce20 100644
--- a/libs/ardour/debug.cc
+++ b/libs/ardour/debug.cc
@@ -53,6 +53,7 @@ PBD::DebugBits PBD::DEBUG::FaderPort = PBD::new_debug_bit ("faderport");
 PBD::DebugBits PBD::DEBUG::FaderPort8 = PBD::new_debug_bit ("faderport8");
 PBD::DebugBits PBD::DEBUG::GenericMidi = PBD::new_debug_bit ("genericmidi");
 PBD::DebugBits PBD::DEBUG::Graph = PBD::new_debug_bit ("graph");
+PBD::DebugBits PBD::DEBUG::IOTaskList = PBD::new_debug_bit ("iotasklist");
 PBD::DebugBits PBD::DEBUG::LTC = PBD::new_debug_bit ("ltc");
 PBD::DebugBits PBD::DEBUG::LV2 = PBD::new_debug_bit ("lv2");
 PBD::DebugBits PBD::DEBUG::LV2Automate = PBD::new_debug_bit ("lv2automate");
diff --git a/libs/ardour/disk_reader.cc b/libs/ardour/disk_reader.cc
index d672bf3da4..bf040cf8b3 100644
--- a/libs/ardour/disk_reader.cc
+++ b/libs/ardour/disk_reader.cc
@@ -49,9 +49,9 @@ using namespace std;
 
 ARDOUR::samplecnt_t   DiskReader::_chunk_samples = default_chunk_samples ();
 PBD::Signal0<void>    DiskReader::Underrun;
-Sample*               DiskReader::_sum_buffer     = 0;
-Sample*               DiskReader::_mixdown_buffer = 0;
-gain_t*               DiskReader::_gain_buffer    = 0;
+thread_local Sample*  DiskReader::_sum_buffer     = 0;
+thread_local Sample*  DiskReader::_mixdown_buffer = 0;
+thread_local gain_t*  DiskReader::_gain_buffer    = 0;
 std::atomic<int>      DiskReader::_no_disk_output (0);
 DiskReader::Declicker DiskReader::loop_declick_in;
 DiskReader::Declicker DiskReader::loop_declick_out;
diff --git a/libs/ardour/globals.cc b/libs/ardour/globals.cc
index 49afbe5cf6..3b8c4889aa 100644
--- a/libs/ardour/globals.cc
+++ b/libs/ardour/globals.cc
@@ -734,11 +734,14 @@ ARDOUR::init (bool try_optimization, const char* localedir, bool with_gui)
 	 * each cycle). Session Export uses one, and the GUI requires
 	 * buffers (for plugin-analysis, auditioner updates) but not
 	 * concurrently.
-	 * Last but not least, the butler needs one for RegionFX.
 	 *
-	 * In theory (hw + 4) should be sufficient, let's add one for luck.
+	 * Last but not least, the butler needs one for RegionFX for
+	 * each I/O thread (up to hardware_concurrency) and one for itself
+	 * (butler's main thread).
+	 *
+	 * In theory (2 * hw + 4) should be sufficient, let's add one for luck.
 	 */
-	BufferManager::init (hardware_concurrency () + 5);
+	BufferManager::init (hardware_concurrency () * 2 + 5);
 
 	PannerManager::instance ().discover_panners ();
 
diff --git a/libs/ardour/io_tasklist.cc b/libs/ardour/io_tasklist.cc
index 8af4a7f4e2..ae86e9a640 100644
--- a/libs/ardour/io_tasklist.cc
+++ b/libs/ardour/io_tasklist.cc
@@ -16,19 +16,72 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#ifdef HAVE_IOPRIO
+#include <sys/syscall.h>
+#endif
+
+#include "pbd/compose.h"
+#include "pbd/cpus.h"
+#include "pbd/debug.h"
+#include "pbd/failed_constructor.h"
 #include "pbd/pthread_utils.h"
 
+#include "temporal/tempo.h"
+
+#include "ardour/debug.h"
+#include "ardour/disk_reader.h"
 #include "ardour/io_tasklist.h"
+#include "ardour/process_thread.h"
+#include "ardour/session_event.h"
 
 using namespace ARDOUR;
 
-IOTaskList::IOTaskList ()
-	: _n_threads (0)
+IOTaskList::IOTaskList (uint32_t n_threads)
+	: _n_threads (n_threads)
+	, _terminate (false)
+	, _exec_sem ("io thread exec", 0)
+	, _idle_sem ("io thread idle", 0)
 {
+	assert (n_threads <= hardware_concurrency ());
+
+	if (n_threads < 2) {
+		return;
+	}
+
+	pthread_attr_t     attr;
+	struct sched_param parm;
+	parm.sched_priority = pbd_absolute_rt_priority (SCHED_RR, pbd_pthread_priority (THREAD_IO));
+
+  pthread_attr_init (&attr);
+#ifdef PLATFORM_WINDOWS
+  pthread_attr_setschedpolicy (&attr, SCHED_OTHER);
+#else
+  pthread_attr_setschedpolicy (&attr, SCHED_RR);
+#endif
+  pthread_attr_setschedparam (&attr, &parm);
+  pthread_attr_setscope (&attr, PTHREAD_SCOPE_SYSTEM);
+  pthread_attr_setinheritsched (&attr, PTHREAD_EXPLICIT_SCHED);
+
+	DEBUG_TRACE (PBD::DEBUG::IOTaskList, string_compose ("IOTaskList starting %1 threads with priority = %2\n", _n_threads, parm.sched_priority));
+
+	_workers.resize (_n_threads);
+	for (uint32_t i = 0; i < _n_threads; ++i) {
+		if (pthread_create (&_workers[i], &attr, &_worker_thread, this)) {
+			throw failed_constructor ();
+		}
+	}
+	pthread_attr_destroy (&attr);
 }
 
 IOTaskList::~IOTaskList ()
 {
+	_terminate.store (true);
+	for (size_t i = 0; i < _workers.size (); ++i) {
+		_exec_sem.signal ();
+	}
+	for (auto const& t : _workers) {
+		pthread_join (t, NULL);
+	}
 }
 
 void
@@ -41,13 +94,78 @@ 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
+		uint32_t wakeup = std::min<uint32_t> (_n_threads, _tasks.size ());
+		DEBUG_TRACE (PBD::DEBUG::IOTaskList, string_compose ("IOTaskList process wakeup %1 thread for %2 tasks.\n", wakeup, _tasks.size ()))
+		for (uint32_t i = 0; i < wakeup; ++i) {
+			_exec_sem.signal ();
+		}
+		for (uint32_t i = 0; i < wakeup; ++i) {
+			_idle_sem.wait ();
+		}
 	} else {
+		DEBUG_TRACE (PBD::DEBUG::IOTaskList, string_compose ("IOTaskList process %1 task(s) in main thread.\n", _tasks.size ()))
 		for (auto const& fn : _tasks) {
 			fn ();
 		}
 	}
 	_tasks.clear ();
 }
+
+void*
+IOTaskList::_worker_thread (void* me)
+{
+	IOTaskList* self = static_cast<IOTaskList*> (me);
+
+	uint32_t id = self->_n_workers.fetch_add (1);
+	char name[64];
+	snprintf (name, 64, "IO-%u-%p", id, (void*)DEBUG_THREAD_SELF);
+	pthread_set_name (name);
+
+	SessionEvent::create_per_thread_pool (name, 64);
+	PBD::notify_event_loops_about_thread_creation (pthread_self (), name, 64);
+
+	DiskReader::allocate_working_buffers ();
+	ARDOUR::ProcessThread* pt = new ProcessThread ();
+	pt->get_buffers ();
+
+#ifdef HAVE_IOPRIO
+	/* compare to Butler::_thread_work */
+  // ioprio_set (IOPRIO_WHO_PROCESS, 0 /*calling thread*/, IOPRIO_PRIO_VALUE (IOPRIO_CLASS_RT, 4))
+  syscall (SYS_ioprio_set, 1, 0, (1 << 13) | 4);
+#endif
+
+	self->io_thread ();
+
+	DiskReader::free_working_buffers ();
+	pt->drop_buffers ();
+	delete pt;
+	return 0;
+}
+
+void
+IOTaskList::io_thread ()
+{
+	while (1) {
+		_exec_sem.wait ();
+		if (_terminate.load ()) {
+			break;
+		}
+
+		Temporal::TempoMap::fetch ();
+
+		while (1) {
+			boost::function<void()> fn;
+			Glib::Threads::Mutex::Lock lm (_tasks_mutex);
+			if (_tasks.empty ()) {
+				break;
+			}
+			fn = _tasks.back ();
+			_tasks.pop_back ();
+			lm.release ();
+
+			fn ();
+		}
+		_idle_sem.signal ();
+	}
+}
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index af1438cbcf..8dab2704e3 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -590,7 +590,8 @@ Session::immediately_post_engine ()
 
 	_process_graph.reset (new Graph (*this));
 	_rt_tasklist.reset (new RTTaskList (_process_graph));
-	_io_tasklist.reset (new IOTaskList ());
+
+	_io_tasklist.reset (new IOTaskList (how_many_io_threads ()));
 
 	/* every time we reconnect, recompute worst case output latencies */
 
@@ -775,8 +776,6 @@ Session::destroy ()
 	_bundles.flush ();
 	_io_plugins.flush ();
 
-	DiskReader::free_working_buffers();
-
 	/* tell everyone who is still standing that we're about to die */
 	drop_references ();
 
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index a74ec00194..9f0bcd9ddf 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -272,7 +272,6 @@ Session::post_engine_init ()
 		_engine.GraphReordered.connect_same_thread (*this, boost::bind (&Session::graph_reordered, this, true));
 		_engine.MidiSelectionPortsChanged.connect_same_thread (*this, boost::bind (&Session::rewire_midi_selection_ports, this));
 
-		DiskReader::allocate_working_buffers();
 		refresh_disk_space ();
 
 		/* we're finally ready to call set_state() ... all objects have
diff --git a/libs/ardour/utils.cc b/libs/ardour/utils.cc
index 9e06652fc4..25b31f4984 100644
--- a/libs/ardour/utils.cc
+++ b/libs/ardour/utils.cc
@@ -696,6 +696,25 @@ ARDOUR::how_many_dsp_threads ()
         return num_threads;
 }
 
+uint32_t
+ARDOUR::how_many_io_threads ()
+{
+	int num_cpu = hardware_concurrency();
+	int pu = Config->get_io_thread_count ();
+	uint32_t num_threads = max (num_cpu - 2, 2);
+	if (pu < 0) {
+		if (-pu < num_cpu) {
+			num_threads = num_cpu + pu;
+		}
+	} else if (pu == 0) {
+		num_threads = num_cpu;
+
+	} else {
+		num_threads = min (num_cpu, pu);
+	}
+	return num_threads;
+}
+
 double
 ARDOUR::gain_to_slider_position_with_max (double g, double max_gain)
 {
diff --git a/libs/pbd/pbd/pthread_utils.h b/libs/pbd/pbd/pthread_utils.h
index ed6628123b..e1b18f2603 100644
--- a/libs/pbd/pbd/pthread_utils.h
+++ b/libs/pbd/pbd/pthread_utils.h
@@ -68,7 +68,8 @@ LIBPBD_API void pthread_set_name (const char* name);
 enum PBDThreadClass {
 	THREAD_MAIN, // main audio I/O thread
 	THREAD_MIDI, // MIDI I/O threads
-	THREAD_PROC // realtime worker
+	THREAD_PROC, // realtime worker
+	THREAD_IO    // non-realtime I/O
 };
 
 LIBPBD_API int pbd_pthread_priority (PBDThreadClass);
diff --git a/libs/pbd/pthread_utils.cc b/libs/pbd/pthread_utils.cc
index 2387bd947f..052d035535 100644
--- a/libs/pbd/pthread_utils.cc
+++ b/libs/pbd/pthread_utils.cc
@@ -280,6 +280,11 @@ pbd_pthread_priority (PBDThreadClass which)
 		default:
 		case THREAD_PROC:
 			return -2;
+		case THREAD_IO:
+			/* https://github.com/mingw-w64/mingw-w64/blob/master/mingw-w64-libraries/winpthreads/src/sched.c
+			 * -> THREAD_PRIORITY_HIGHEST
+			 */
+			return -13;
 	}
 #else
 	int base = -20;
@@ -299,6 +304,8 @@ pbd_pthread_priority (PBDThreadClass which)
 		default:
 		case THREAD_PROC:
 			return base - 2;
+		case THREAD_IO:
+			return base - 10;
 	}
 #endif
 }

From 2ccda116c7409a707c76dd4d5b77c720c7ff6a1d Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 30 Apr 2024 03:54:57 +0200
Subject: [PATCH 07/13] Add preference for I/O thread count

---
 gtk2_ardour/rc_option_editor.cc | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/gtk2_ardour/rc_option_editor.cc b/gtk2_ardour/rc_option_editor.cc
index 0385778c5c..ffaa8e3497 100644
--- a/gtk2_ardour/rc_option_editor.cc
+++ b/gtk2_ardour/rc_option_editor.cc
@@ -4906,6 +4906,27 @@ These settings will only take effect after %1 is restarted.\n\
 
 	add_option (_("Performance"), new BufferingOptions (_rc_config));
 
+	if (hwcpus > 1) {
+		ComboOption<int32_t>* procs = new ComboOption<int32_t> (
+				"io-thread-count",
+				_("Disk I/O threads"),
+				sigc::mem_fun (*_rc_config, &RCConfiguration::get_io_thread_count),
+				sigc::mem_fun (*_rc_config, &RCConfiguration::set_io_thread_count)
+				);
+
+		procs->add (-2, _("all but two processor"));
+		procs->add (-1, _("all but one processor"));
+		procs->add (0, _("all available processors"));
+
+		for (uint32_t i = 1; i <= hwcpus; ++i) {
+			procs->add (i, string_compose (P_("%1 processor", "%1 processors", i), i));
+		}
+
+		procs->set_note (string_compose (_("This setting will only take effect when %1 is restarted."), PROGRAM_NAME));
+
+		add_option (_("Performance"), procs);
+	}
+
 	/* Image cache size */
 	add_option (_("Performance"), new OptionEditorHeading (_("Memory Usage")));
 

From b9da1a5bd5a58550c6f6151d763547ec8dd65583 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Wed, 1 May 2024 03:51:42 +0200
Subject: [PATCH 08/13] Expose HW concurrency to LV2 plugins

---
 libs/ardour/lv2_plugin.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libs/ardour/lv2_plugin.cc b/libs/ardour/lv2_plugin.cc
index de50c3f8e9..489604ed4d 100644
--- a/libs/ardour/lv2_plugin.cc
+++ b/libs/ardour/lv2_plugin.cc
@@ -610,6 +610,7 @@ LV2Plugin::init(const void* c_plugin, samplecnt_t rate)
 	static const int32_t _max_block_length = 8192; // max possible (with all engines and during export)
 	static const int32_t rt_policy = PBD_SCHED_FIFO;
 	static const int32_t rt_priority = pbd_absolute_rt_priority (PBD_SCHED_FIFO, AudioEngine::instance()->client_real_time_priority () - 1);
+	static const int32_t hw_concurrency = how_many_dsp_threads ();
 	/* Consider updating max-block-size whenever the buffersize changes.
 	 * It requires re-instantiating the plugin (which is a non-realtime operation),
 	 * so it should be done lightly and only for plugins that require it.
@@ -632,6 +633,8 @@ LV2Plugin::init(const void* c_plugin, samplecnt_t rate)
 		  sizeof(int32_t), atom_Int, &rt_policy },
 		{ LV2_OPTIONS_INSTANCE, 0, _uri_map.uri_to_id("http://ardour.org/lv2/threads/#schedPriority"),
 		  sizeof(int32_t), atom_Int, &rt_priority },
+		{ LV2_OPTIONS_INSTANCE, 0, _uri_map.uri_to_id("http://ardour.org/lv2/threads/#concurrency"),
+		  sizeof(int32_t), atom_Int, &hw_concurrency },
 		{ LV2_OPTIONS_INSTANCE, 0, _uri_map.uri_to_id("http://lv2plug.in/ns/extensions/ui#backgroundColor"),
 		  sizeof(int32_t), atom_Int, &_ui_background_color },
 		{ LV2_OPTIONS_INSTANCE, 0, _uri_map.uri_to_id("http://lv2plug.in/ns/extensions/ui#foregroundColor"),

From f35555183934b0b990a9517a506a1f5363c76c4d Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Wed, 1 May 2024 14:54:31 +0200
Subject: [PATCH 09/13] Don't nag Trax users after export

---
 gtk2_ardour/export_dialog.cc        | 2 +-
 gtk2_ardour/simple_export_dialog.cc | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/gtk2_ardour/export_dialog.cc b/gtk2_ardour/export_dialog.cc
index fc1d26f7ea..ef466f4305 100644
--- a/gtk2_ardour/export_dialog.cc
+++ b/gtk2_ardour/export_dialog.cc
@@ -477,7 +477,7 @@ ExportDialog::show_progress ()
 
 	if (!status->aborted()) {
 		hide();
-		if (!ARDOUR::Profile->get_mixbus()) {
+		if (!ARDOUR::Profile->get_mixbus () && !ARDOUR::Profile->get_livetrax ()) {
 			NagScreen* ns = NagScreen::maybe_nag (_("export"));
 			if (ns) {
 				ns->nag ();
diff --git a/gtk2_ardour/simple_export_dialog.cc b/gtk2_ardour/simple_export_dialog.cc
index 98b417eec6..8318843751 100644
--- a/gtk2_ardour/simple_export_dialog.cc
+++ b/gtk2_ardour/simple_export_dialog.cc
@@ -345,7 +345,7 @@ SimpleExportDialog::start_export ()
 		if (_post_export_combo.get_active_row_number () == 0) {
 			PBD::open_folder (folder ());
 		}
-		if (!ARDOUR::Profile->get_mixbus ()) {
+		if (!ARDOUR::Profile->get_mixbus () && !ARDOUR::Profile->get_livetrax ()) {
 			NagScreen* ns = NagScreen::maybe_nag (_("Export"));
 			if (ns) {
 				ns->nag ();

From 99e2ac28e1a07c37dfaf057fb3068ff02f7e682d Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Wed, 1 May 2024 22:30:04 +0200
Subject: [PATCH 10/13] Update debug message to include regionfx and offset

---
 libs/ardour/audioregion.cc | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libs/ardour/audioregion.cc b/libs/ardour/audioregion.cc
index 6944e05bca..3f5aaa82b3 100644
--- a/libs/ardour/audioregion.cc
+++ b/libs/ardour/audioregion.cc
@@ -669,9 +669,6 @@ AudioRegion::read_at (Sample*     buf,
 		uint32_t fx_latency = _fx_latency;
 		lm.release ();
 
-		DEBUG_TRACE (DEBUG::AudioPlayback, string_compose ("Region '%1' channel: %2 read at %3 - %4 to_read: %5 with fx: %6\n",
-		             name(), chan_n, internal_offset, internal_offset + to_read, to_read, have_fx));
-
 		ChanCount cc (DataType::AUDIO, n_channels ());
 		_readcache.ensure_buffers (cc, to_read + _fx_latency);
 
@@ -698,6 +695,9 @@ AudioRegion::read_at (Sample*     buf,
 			n_read = max<samplecnt_t> (0, min (to_read, lsamples - offset));
 		}
 
+		DEBUG_TRACE (DEBUG::AudioPlayback, string_compose ("Region '%1' channel: %2 read: %3 - %4 (%5) to_read: %6 offset: %7 with fx: %8 fx_latency: %9\n",
+		             name(), chan_n, readat, readat + n_read, n_read, to_read, internal_offset, have_fx, fx_latency));
+
 		_readcache.ensure_buffers (cc, n_proc);
 
 		if (n_read < n_proc) {

From 631ee17e341bc39a91a1afc2e927720438f2c0ec Mon Sep 17 00:00:00 2001
From: John Emmas <john@creativepost.co.uk>
Date: Thu, 2 May 2024 10:22:44 +0100
Subject: [PATCH 11/13] Modify class ARDOUR::DiskReader because it now includes
 members declared using 'thread_local'

On Windows, variables defined as having thread storage can have a different address in different threads and as such, they aren't allowed to be imported or exported from a DLL.
---
 libs/ardour/ardour/disk_reader.h | 88 ++++++++++++++++----------------
 1 file changed, 44 insertions(+), 44 deletions(-)

diff --git a/libs/ardour/ardour/disk_reader.h b/libs/ardour/ardour/disk_reader.h
index 63797e8685..29d5c2164f 100644
--- a/libs/ardour/ardour/disk_reader.h
+++ b/libs/ardour/ardour/disk_reader.h
@@ -38,72 +38,72 @@ class MidiPlaylist;
 
 template <typename T> class MidiRingBuffer;
 
-class LIBARDOUR_API DiskReader : public DiskIOProcessor
+class /*LIBARDOUR_API*/ DiskReader : public DiskIOProcessor
 {
 public:
-	DiskReader (Session&, Track&, std::string const& name, Temporal::TimeDomainProvider const &, DiskIOProcessor::Flag f = DiskIOProcessor::Flag (0));
-	~DiskReader ();
+	LIBARDOUR_API DiskReader (Session&, Track&, std::string const& name, Temporal::TimeDomainProvider const &, DiskIOProcessor::Flag f = DiskIOProcessor::Flag (0));
+	LIBARDOUR_API ~DiskReader ();
 
-	bool set_name (std::string const& str);
+	LIBARDOUR_API bool set_name (std::string const& str);
 
-	std::string display_name () const;
+	LIBARDOUR_API std::string display_name () const;
 
-	static samplecnt_t chunk_samples ()
+	LIBARDOUR_API static samplecnt_t chunk_samples ()
 	{
 		return _chunk_samples;
 	}
 
-	static void set_chunk_samples (samplecnt_t n)
+	LIBARDOUR_API static void set_chunk_samples (samplecnt_t n)
 	{
 		_chunk_samples = n;
 	}
 
-	static samplecnt_t default_chunk_samples ();
+	LIBARDOUR_API static samplecnt_t default_chunk_samples ();
 
-	void run (BufferSet& /*bufs*/, samplepos_t /*start_sample*/, samplepos_t /*end_sample*/, double speed, pframes_t /*nframes*/, bool /*result_required*/);
-	void realtime_handle_transport_stopped ();
-	void realtime_locate (bool);
-	bool overwrite_existing_buffers ();
-	void set_pending_overwrite (OverwriteReason);
-	void set_loop (Location*);
+	LIBARDOUR_API void run (BufferSet& /*bufs*/, samplepos_t /*start_sample*/, samplepos_t /*end_sample*/, double speed, pframes_t /*nframes*/, bool /*result_required*/);
+	LIBARDOUR_API void realtime_handle_transport_stopped ();
+	LIBARDOUR_API void realtime_locate (bool);
+	LIBARDOUR_API bool overwrite_existing_buffers ();
+	LIBARDOUR_API void set_pending_overwrite (OverwriteReason);
+	LIBARDOUR_API void set_loop (Location*);
 
-	int set_state (const XMLNode&, int version);
+	LIBARDOUR_API int set_state (const XMLNode&, int version);
 
 	PBD::Signal0<void> AlignmentStyleChanged;
 
-	float buffer_load () const;
+	LIBARDOUR_API float buffer_load () const;
 
-	void move_processor_automation (std::weak_ptr<Processor>, std::list<Temporal::RangeMove> const&);
+	LIBARDOUR_API void move_processor_automation (std::weak_ptr<Processor>, std::list<Temporal::RangeMove> const&);
 
 	/* called by the Butler in a non-realtime context as part of its normal
 	 * buffer refill loop (not due to transport-mechanism requests like
 	 * locate)
 	 */
-	int do_refill ();
+	LIBARDOUR_API int do_refill ();
 
 	/** For contexts outside the normal butler refill loop (allocates temporary working buffers) */
 	int do_refill_with_alloc (bool partial_fill, bool reverse);
 
-	bool pending_overwrite () const;
+	LIBARDOUR_API bool pending_overwrite () const;
 
 	/* Working buffers for do_refill (butler thread) */
-	static void allocate_working_buffers ();
-	static void free_working_buffers ();
+	LIBARDOUR_API static void allocate_working_buffers ();
+	LIBARDOUR_API static void free_working_buffers ();
 
-	void adjust_buffering ();
+	LIBARDOUR_API void adjust_buffering ();
 
-	bool can_internal_playback_seek (sampleoffset_t distance);
-	void internal_playback_seek (sampleoffset_t distance);
-	int  seek (samplepos_t sample, bool complete_refill = false);
+	LIBARDOUR_API bool can_internal_playback_seek (sampleoffset_t distance);
+	LIBARDOUR_API void internal_playback_seek (sampleoffset_t distance);
+	LIBARDOUR_API int  seek (samplepos_t sample, bool complete_refill = false);
 
-	static PBD::Signal0<void> Underrun;
+	LIBARDOUR_API static PBD::Signal0<void> Underrun;
 
-	void playlist_modified ();
-	void reset_tracker ();
+	LIBARDOUR_API void playlist_modified ();
+	LIBARDOUR_API void reset_tracker ();
 
-	bool declick_in_progress () const;
+	LIBARDOUR_API bool declick_in_progress () const;
 
-	void set_need_midi_catchup (bool);
+	LIBARDOUR_API void set_need_midi_catchup (bool);
 
 	/* inc/dec variants MUST be called as part of the process call tree, before any
 	 * disk readers are invoked. We use it when the session needs the
@@ -112,21 +112,21 @@ public:
 	 * don't want any actual disk output yet because we are still not
 	 * synced.
 	 */
-	static void inc_no_disk_output ();
-	static void dec_no_disk_output ();
-	static bool no_disk_output ()
+	LIBARDOUR_API static void inc_no_disk_output ();
+	LIBARDOUR_API static void dec_no_disk_output ();
+	LIBARDOUR_API static bool no_disk_output ()
 	{
 		return _no_disk_output.load ();
 	}
-	static void reset_loop_declick (Location*, samplecnt_t sample_rate);
-	static void alloc_loop_declick (samplecnt_t sample_rate);
+	LIBARDOUR_API static void reset_loop_declick (Location*, samplecnt_t sample_rate);
+	LIBARDOUR_API static void alloc_loop_declick (samplecnt_t sample_rate);
 
 protected:
 	friend class Track;
 	friend class MidiTrack;
 
 	struct ReaderChannelInfo : public DiskIOProcessor::ChannelInfo {
-		ReaderChannelInfo (samplecnt_t buffer_size, samplecnt_t preloop_size)
+		LIBARDOUR_API ReaderChannelInfo (samplecnt_t buffer_size, samplecnt_t preloop_size)
 			: DiskIOProcessor::ChannelInfo (buffer_size)
 			, pre_loop_buffer (0)
 			, pre_loop_buffer_size (0)
@@ -135,27 +135,27 @@ protected:
 			resize (buffer_size);
 		}
 
-		~ReaderChannelInfo ()
+		LIBARDOUR_API ~ReaderChannelInfo ()
 		{
 			delete[] pre_loop_buffer;
 		}
 
-		void resize (samplecnt_t);
-		void resize_preloop (samplecnt_t);
+		LIBARDOUR_API void resize (samplecnt_t);
+		LIBARDOUR_API void resize_preloop (samplecnt_t);
 
 		Sample*     pre_loop_buffer;
 		samplecnt_t pre_loop_buffer_size;
 		bool        initialized;
 	};
 
-	XMLNode& state () const;
+	LIBARDOUR_API XMLNode& state () const;
 
-	void resolve_tracker (Evoral::EventSink<samplepos_t>& buffer, samplepos_t time);
+	LIBARDOUR_API void resolve_tracker (Evoral::EventSink<samplepos_t>& buffer, samplepos_t time);
 
-	int  use_playlist (DataType, std::shared_ptr<Playlist>);
-	void playlist_ranges_moved (std::list<Temporal::RangeMove> const&, bool);
+	LIBARDOUR_API int  use_playlist (DataType, std::shared_ptr<Playlist>);
+	LIBARDOUR_API void playlist_ranges_moved (std::list<Temporal::RangeMove> const&, bool);
 
-	int add_channel_to (std::shared_ptr<ChannelList>, uint32_t how_many);
+	LIBARDOUR_API int add_channel_to (std::shared_ptr<ChannelList>, uint32_t how_many);
 
 	class DeclickAmp
 	{

From a88d430609aa34343b8ce1481145fa2ab19f6ffb Mon Sep 17 00:00:00 2001
From: Ben Loftis <ben@harrisonconsoles.com>
Date: Thu, 2 May 2024 12:42:23 -0500
Subject: [PATCH 12/13] null check for a missing session (for LT)

---
 gtk2_ardour/editor_sections.cc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/gtk2_ardour/editor_sections.cc b/gtk2_ardour/editor_sections.cc
index 1fafdcf1bd..d8709e0430 100644
--- a/gtk2_ardour/editor_sections.cc
+++ b/gtk2_ardour/editor_sections.cc
@@ -228,6 +228,10 @@ EditorSections::scroll_row_timeout ()
 void
 EditorSections::update_time_selection ()
 {
+	if (!_session) {
+		return;
+	}
+
 	_view.get_selection ()->unselect_all ();
 
 	Selection& selection (PublicEditor::instance ().get_selection ());
@@ -256,6 +260,10 @@ EditorSections::update_time_selection ()
 void
 EditorSections::selection_changed ()
 {
+	if (!_session) {
+		return;
+	}
+
 	TreeView::Selection::ListHandle_Path rows = _view.get_selection ()->get_selected_rows ();
 	if (rows.empty ()) {
 		return;

From 27e2348b47cc10f8a03be6fbc4a82d9f743d83cd Mon Sep 17 00:00:00 2001
From: Ben Loftis <ben@harrisonconsoles.com>
Date: Thu, 2 May 2024 12:43:12 -0500
Subject: [PATCH 13/13] when capturing a midi pgm change, display the pgm num
 (for LT)

---
 libs/ardour/midi_scene_changer.cc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libs/ardour/midi_scene_changer.cc b/libs/ardour/midi_scene_changer.cc
index 14d0ea6328..d791c1275a 100644
--- a/libs/ardour/midi_scene_changer.cc
+++ b/libs/ardour/midi_scene_changer.cc
@@ -339,6 +339,7 @@ MIDISceneChanger::program_change_input (MIDI::Parser& parser, MIDI::byte program
 	}
 
 	loc->set_scene_change (std::shared_ptr<MIDISceneChange> (msc));
+	loc->set_name( string_compose(_("scene [%1]"), 1+bank*128+(program & 0x7f)));
 
 	/* this will generate a "changed" signal to be emitted by locations,
 	   and we will call ::gather() to update our list of MIDI events.