diff --git a/libs/ardour/ardour/debug.h b/libs/ardour/ardour/debug.h
index 18aaa74ae7..a8e127a187 100644
--- a/libs/ardour/ardour/debug.h
+++ b/libs/ardour/ardour/debug.h
@@ -34,6 +34,7 @@ namespace PBD {
 	namespace DEBUG {
 		LIBARDOUR_API extern DebugBits AudioEngine;
 		LIBARDOUR_API extern DebugBits AudioPlayback;
+		LIBARDOUR_API extern DebugBits AudioCacheRefill;
 		LIBARDOUR_API extern DebugBits AudioUnitConfig;
 		LIBARDOUR_API extern DebugBits AudioUnitGUI;
 		LIBARDOUR_API extern DebugBits AudioUnitProcess;
diff --git a/libs/ardour/audio_playlist.cc b/libs/ardour/audio_playlist.cc
index 67b391c384..b3a2e3bfc2 100644
--- a/libs/ardour/audio_playlist.cc
+++ b/libs/ardour/audio_playlist.cc
@@ -178,6 +178,13 @@ AudioPlaylist::read (Sample *buf, Sample *mixdown_buffer, float *gain_buffer, ti
 	DEBUG_TRACE (DEBUG::AudioPlayback, string_compose ("Playlist %1 read @ %2 for %3, channel %4, regions %5 mixdown @ %6 gain @ %7\n",
 							   name(), start.samples(), cnt.samples(), chan_n, regions.size(), mixdown_buffer, gain_buffer));
 
+	DEBUG_TRACE (DEBUG::AudioCacheRefill, string_compose ("Playlist '%1' chn: %2 from %3 to %4 [s] PH@ %5\n",
+				name (), chan_n,
+				std::setprecision (3), std::fixed,
+				start.samples() / (float)_session.sample_rate (),
+				(start.samples() + cnt.samples()) / (float)_session.sample_rate (),
+				_session.transport_sample () / (float)_session.sample_rate ()));
+
 	samplecnt_t const scnt (cnt.samples ());
 
 	/* optimizing this memset() away involves a lot of conditionals
diff --git a/libs/ardour/audioregion.cc b/libs/ardour/audioregion.cc
index 38ce0c36a7..89d79c6579 100644
--- a/libs/ardour/audioregion.cc
+++ b/libs/ardour/audioregion.cc
@@ -610,6 +610,11 @@ AudioRegion::read_at (Sample*     buf,
 	   The caller has verified that we cover the desired section.
 	*/
 
+	DEBUG_TRACE (DEBUG::AudioCacheRefill, string_compose ("- Region '%1' chn: %2 from %3 to %4 [s]\n",
+				name(), chan_n,
+				std::setprecision (3), std::fixed,
+				pos / (float)_session.sample_rate (), (pos + cnt) / (float)_session.sample_rate ()));
+
 	/* See doc/region_read.svg for a drawing which might help to explain
 	   what is going on.
 	*/
diff --git a/libs/ardour/debug.cc b/libs/ardour/debug.cc
index 99a8dbce20..2cb4becc65 100644
--- a/libs/ardour/debug.cc
+++ b/libs/ardour/debug.cc
@@ -29,6 +29,7 @@ using namespace std;
 
 PBD::DebugBits PBD::DEBUG::AudioEngine = PBD::new_debug_bit ("AudioEngine");
 PBD::DebugBits PBD::DEBUG::AudioPlayback = PBD::new_debug_bit ("audioplayback");
+PBD::DebugBits PBD::DEBUG::AudioCacheRefill = PBD::new_debug_bit ("audiocacherefill");
 PBD::DebugBits PBD::DEBUG::AudioUnitConfig = PBD::new_debug_bit ("AudioUnitConfig");
 PBD::DebugBits PBD::DEBUG::AudioUnitGUI = PBD::new_debug_bit ("AudioUnitGUI");
 PBD::DebugBits PBD::DEBUG::AudioUnitProcess = PBD::new_debug_bit ("AudioUnitProcess");
diff --git a/libs/ardour/disk_reader.cc b/libs/ardour/disk_reader.cc
index d812648759..57976725cb 100644
--- a/libs/ardour/disk_reader.cc
+++ b/libs/ardour/disk_reader.cc
@@ -423,6 +423,10 @@ DiskReader::run (BufferSet& bufs, samplepos_t start_sample, samplepos_t end_samp
 					cerr << "underrun for " << _name << " Available samples: " << available << " required: " << disk_samples_to_consume << endl;
 #endif
 					DEBUG_TRACE (DEBUG::Butler, string_compose ("%1 underrun in %2, total space = %3 vs %4\n", DEBUG_THREAD_SELF, name (), available, disk_samples_to_consume));
+					DEBUG_TRACE (DEBUG::AudioCacheRefill, string_compose ("DR '%1' underrun have %2 need %3 samples at pos %4\n",
+								name (), available, disk_samples_to_consume,
+								std::setprecision (3), std::fixed,
+								start_sample / (float)_session.sample_rate ()));
 					Underrun ();
 					return;
 				}