ardour/livetrax
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explain midi starvation, issue #6170

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this is not a fix yet, just some comments and
code cleanup done while reading/investigating:

* limit reads to available write-space
* skip inactive tracks
* handle potential unsigned + negative value.
This commit is contained in:
Robin Gareus 2015-03-12 14:16:55 +01:00
parent 831f2989ac
commit a16dd7c071
1 changed files with 31 additions and 3 deletions
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34
libs/ardour/midi_diskstream.cc
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@ -579,6 +579,10 @@ MidiDiskstream::commit (framecnt_t playback_distance)
{ {
bool need_butler = false; bool need_butler = false;
if (!_io || !_io->active()) {
return false;
}
if (_actual_speed < 0.0) { if (_actual_speed < 0.0) {
playback_sample -= playback_distance; playback_sample -= playback_distance;
} else { } else {
@ -606,10 +610,33 @@ MidiDiskstream::commit (framecnt_t playback_distance)
* need the butler is done correctly. * need the butler is done correctly.
*/ */
/* furthermore..
*
* Doing heavy GUI operations[1] can stall also the butler.
* The RT-thread meanwhile will happily continue and
* ‘frames_read’ (from buffer to output) will become larger
* than ‘frames_written’ (from disk to buffer).
*
* The disk-stream is now behind..
*
* In those cases the butler needs to be summed to refill the buffer (done now)
* AND we need to skip (frames_read - frames_written). ie remove old events
* before playback_sample from the rinbuffer. (not yet done)
*
* [1] one way to do so is described at #6170.
* For me just popping up the context-menu on a MIDI-track header
* of a track with a large (think beethoven :) midi-region also did the
* trick. The playhead stalls for 2 or 3 sec, until the context-menu shows.
*
* In both cases the root cause is that redrawing MIDI regions on the GUI is still very slow
* and can stall
*/
if (frames_read <= frames_written) { if (frames_read <= frames_written) {
if ((frames_written - frames_read) + playback_distance < midi_readahead) { if ((frames_written - frames_read) + playback_distance < midi_readahead) {
need_butler = true; need_butler = true;
} }
} else {
need_butler = true;
} }
@ -812,16 +839,17 @@ MidiDiskstream::do_refill ()
uint32_t frames_read = g_atomic_int_get(&_frames_read_from_ringbuffer); uint32_t frames_read = g_atomic_int_get(&_frames_read_from_ringbuffer);
uint32_t frames_written = g_atomic_int_get(&_frames_written_to_ringbuffer); uint32_t frames_written = g_atomic_int_get(&_frames_written_to_ringbuffer);
if ((frames_written - frames_read) >= midi_readahead) { if ((frames_read < frames_written) && (frames_written - frames_read) >= midi_readahead) {
return 0; return 0;
} }
framecnt_t to_read = midi_readahead - (frames_written - frames_read); framecnt_t to_read = midi_readahead - ((framecnt_t)frames_written - (framecnt_t)frames_read);
//cout << "MDS read for midi_readahead " << to_read << " rb_contains: " //cout << "MDS read for midi_readahead " << to_read << " rb_contains: "
// << frames_written - frames_read << endl; // << frames_written - frames_read << endl;
to_read = (framecnt_t) min ((framecnt_t) to_read, (framecnt_t) (max_framepos - file_frame)); to_read = min (to_read, (framecnt_t) (max_framepos - file_frame));
to_read = min (to_read, (framecnt_t) write_space);
if (read (file_frame, to_read, reversed)) { if (read (file_frame, to_read, reversed)) {
ret = -1; ret = -1;