Some further notes (and experiments) on optimizations

diff --git a/libs/ardour/port_manager.cc b/libs/ardour/port_manager.cc
index 98b85e03b7f40e687564e009a5c73cb2fa4beafc..df6eee247b6ef115dc7f41eb7f8ff5c3de3f9555 100644 (file)
--- a/libs/ardour/port_manager.cc
+++ b/libs/ardour/port_manager.cc
@@ -755,7 +755,7 @@ PortManager::cycle_start (pframes_t nframes, Session* s)
 
        /* TODO optimize
         *  - when speed == 1.0, the resampler copies data without processing
-        *   it may be more efficient to just run all in sequence
+        *   it may (or may not) be more efficient to just run all in sequence.
         *
         *  - single sequential task for 'lightweight' tasks would make sense
         *    (run it in parallel with 'heavy' resampling.
@@ -766,8 +766,13 @@ PortManager::cycle_start (pframes_t nframes, Session* s)
         *    amount of work (how many connected ports are there, how
         *    many resamplers need to run) vs. available CPU cores and semaphore
         *    synchronization overhead.
+        *
+        *  - input ports: it would make sense to resample each input only once
+        *    (rather than resample into each ardour-owned input port).
+        *    A single external source-port may be connected to many ardour
+        *    input-ports. Currently re-sampling is per input.
         */
-       if (s && s->rt_tasklist () /* && fabs (Port::speed_ratio ()) != 1.0 */) {
+       if (s && s->rt_tasklist () && fabs (Port::speed_ratio ()) != 1.0) {
                RTTaskList::TaskList tl;
                for (Ports::iterator p = _cycle_ports->begin(); p != _cycle_ports->end(); ++p) {
                        tl.push_back (boost::bind (&Port::cycle_start, p->second, nframes));
@@ -784,7 +789,7 @@ void
 PortManager::cycle_end (pframes_t nframes, Session* s)
 {
        // see optimzation note in ::cycle_start()
-       if (s && s->rt_tasklist () /* && fabs (Port::speed_ratio ()) != 1.0 */) {
+       if (s && s->rt_tasklist () && fabs (Port::speed_ratio ()) != 1.0) {
                RTTaskList::TaskList tl;
                for (Ports::iterator p = _cycle_ports->begin(); p != _cycle_ports->end(); ++p) {
                        tl.push_back (boost::bind (&Port::cycle_end, p->second, nframes));
@@ -887,7 +892,7 @@ void
 PortManager::cycle_end_fade_out (gain_t base_gain, gain_t gain_step, pframes_t nframes, Session* s)
 {
        // see optimzation note in ::cycle_start()
-       if (s && s->rt_tasklist () /* && fabs (Port::speed_ratio ()) != 1.0 */) {
+       if (s && s->rt_tasklist () && fabs (Port::speed_ratio ()) != 1.0) {
                RTTaskList::TaskList tl;
                for (Ports::iterator p = _cycle_ports->begin(); p != _cycle_ports->end(); ++p) {
                        tl.push_back (boost::bind (&Port::cycle_end, p->second, nframes));