"Server synchronous mode" Option in Jack - What is it doing?

[lilith]

I posted the same in the Reaper forum, but as it offers some solution I also post it here. I have no clue though why it's working. So if anyone have the explanation I'm curious

I currently have a Reaper project with an average RT DSP load of ~10%. When moving the playhead (i.e. jumping to another position) however the DSP load peaks at ~95% sometimes. That caused basically xruns and short clicks everytime I moved the playhead. This only happens when using Jack, with Alsa everyting is fine.

When I move the playhead during the track is playing the increase in DSP load is very little when moving the playhead. It's much worse when the transport is stopped.

Now I activated the option "Server synchronous mode" in Jack and the xruns are gone!

I opened a similar thread some time ago:
https://forum.cockos.com/showthread.php?t=222259

Let's see if this also affects the pulse audio issue.

Does anyone have an explanation for that behaviour and also why there's this huge DSP load when "just" moving the playhead?

Is it normal that I cannot do any selection for the Clock Source setting? Does one need this?
My interface is the Roland Rubix 24.

[lilith]

Mh... this seems to make another issue:

Code: Select all

Sun May 17 02:18:54 2020: ERROR: JackFreewheelDriver::ProcessSync: SuspendRefNum error
Sun May 17 02:18:54 2020: ERROR: JackAudioDriver::ProcessGraphSync: ProcessWriteSlaves error, engine may now behave abnormally!!
Sun May 17 02:18:54 2020: ERROR: JackPosixProcessSync::LockedTimedWait error usec = 5000000 err = Connection timed out
Sun May 17 02:18:54 2020: ERROR: JackEngine::ClientDeactivate wait error ref = 6 name = REAPER
Sun May 17 02:18:54 2020: ERROR: JackEngine::ClientKill ref = 6 cannot be removed from the graph !!
Sun May 17 02:18:54 2020: ERROR: Failed to find port 'REAPER:MIDI Input 1' to destroy
Sun May 17 02:18:54 2020: ERROR: Failed to find port 'REAPER:MIDI Input 2' to destroy
Sun May 17 02:18:54 2020: ERROR: Failed to find port 'REAPER:in1' to destroy
Sun May 17 02:18:54 2020: ERROR: Failed to find port 'REAPER:in2' to destroy
Sun May 17 02:18:54 2020: ERROR: Failed to find port 'REAPER:out1' to destroy
Sun May 17 02:18:54 2020: ERROR: Failed to find port 'REAPER:out2' to destroy
Sun May 17 02:18:55 2020: ERROR: JackPosixProcessSync::LockedTimedWait error usec = 1000000 err = Connection timed out
Sun May 17 02:18:55 2020: ERROR: JackEngine::ClientCloseAux wait error ref = 6
Sun May 17 02:18:55 2020: Client 'REAPER' with PID 8693 is out
Sun May 17 02:18:59 2020: ERROR: JackAudioDriver::ProcessGraphSync: SuspendRefNum error, engine may now behave abnormally!!

Never seen such error messages.

[lad]

Hey Lilith, I'm a recent buster convert. Have you ever tried the liquorix kernel? It may be worth the effort to try it out sometime. I found that it works very well.
Cheers

[lilith]

Hey Lilith, I'm a recent buster convert. Have you ever tried the liquorix kernel? It may be worth the effort to try it out sometime. I found that it works very well.
Cheers

Hi lad,

not yet. Do you think it's a kernel issue? I tried the AVlinux kernel last time. I could test if it helps. Also I think I didn't test the synchronous mode with the stock RT kernel.

[lad]

Sorry if i missed it, which kernel are your initial results from? What are your pc specs?

Regarding the system clock setting question... that seems "normal" to me because that's what happens here too. If i try to select a clock source, it doesn't *seem* to persist, the UI just forgets. I also have reaper and tried to scrub around like you tried, but I didn't get any xruns or dsp increase (under liquorix kernel). I will try on the realtime kernel as well and report back. In general I am recommending liquorix because I am quite pleased in its overall performance.

[lilith]

Sorry if i missed it, which kernel are your initial results from? What are your pc specs?

Regarding the system clock setting question... that seems "normal" to me because that's what happens here too. If i try to select a clock source, it doesn't *seem* to persist, the UI just forgets. I also have reaper and tried to scrub around like you tried, but I didn't get any xruns or dsp increase (under liquorix kernel). I will try on the realtime kernel as well and report back. In general I am recommending liquorix because I am quite pleased in its overall performance.

The errors from above I got with the stock Debian non RT kernel. PC is an i5 from 2015 with intel onboard graphics.

In order to reproduce it in Reaper you have to bring the RT cpu load to ~40% and use plugins with high PDC values (i guess that plays a role), e.g. Diva, Repro, etc.. It does not happen with pure audio or plugins like zynfusion. I' m testing the performance with Alsa and see how it goes the next days.

[lad]

Hmm, in my experience the default stock kernel was not worth the effort/time to optimize. I installed the real-time kernel and liquorix then uninstalled the stock.

[puleglot]

Is it normal that I cannot do any selection for the Clock Source setting? Does one need this?
My interface is the Roland Rubix 24.

Roland Rubix doesn't have a digital input or word clock input, so it can only use internal clock.