add a new "Run Loop" timing stats for ALSA and JACK backends

libs/ardour/ardour/audio_backend.h

@@ -851,11 +851,12 @@ public:
 
 	enum TimingTypes {
 		DeviceWait = 0,
-		PreProcess = 1,
-		ProcessCallback = 2,
-		PostProcess = 3,
+		PreProcess,
+		ProcessCallback,
+		PostProcess,
+		RunLoop,
 		/* end */
-		NTT = 4
+		NTT
 	};
 
 	PBD::TimingStats dsp_stats[NTT];

libs/backends/alsa/alsa_audiobackend.cc

@@ -1855,6 +1855,7 @@ AlsaAudioBackend::main_process_thread ()
 			dsp_stats[DeviceWait].start();
 			nr = _pcmi->pcm_wait ();
 			dsp_stats[DeviceWait].update();
+			dsp_stats[RunLoop].start ();
 
 			/* update DLL */
 			dsp_stats[PreProcess].start();
@@ -2021,6 +2022,7 @@ AlsaAudioBackend::main_process_thread ()
 				++last_n_periods;
 
 				dsp_stats[PostProcess].update ();
+				dsp_stats[RunLoop].update ();
 			}
 
 			if (xrun && (_pcmi->capt_xrun () > 0 || _pcmi->play_xrun () > 0)) {

libs/backends/jack/jack_audiobackend.cc

@@ -977,6 +977,7 @@ JACKAudioBackend::process_thread ()
         AudioEngine::thread_init_callback (this);
 
         while (1) {
+                TimerRAII ltr (dsp_stats[RunLoop]);
                 GET_PRIVATE_JACK_POINTER_RET(_priv_jack,0);
 
                 dsp_stats[AudioBackend::DeviceWait].start ();