Intervallic xruns with A TWIST!

[thoth_mcdonalds]

Hey folks... I'm a long time lurker on these system tuning threads and I haven't seen anyone describe anything quite like this.

Like many other users, I experience xruns at VERY predictable intervals. At my preferred setting for recording I experience xruns every 1m20s.

HOWEVER, if I increase the buffer, the duration between xruns (roughly) doubles. Increase buffer by one more increment and again it doubles and so on and so on.

Likewise, changing the sampling rate has the same effect.

Do you think I would be right to assume this has to do with the interface?

The interface is a MOTU828mkii (FireWire, and yes my card has a TI chip!) I've definitely experienced frequent xruns before, but not in such a measurable and predictable way. This piece of gear had been very solid for me and I think I've used it for 7 or 8 years now? It is def old and not in the list of tested interfaces in ffado.

I want to keep this post as short and sweet as possible so I don't want to overload you with all the details of my set up and logs just yet. Mostly interested in your thoughts on my question (bold for emphasis.)

Thanks, fam!

[thoth_mcdonalds]

I beg your pardon, I meant to say the interval increases by double when I increase the Frames/period. Increasing the periods/buffer has a similar effect but I have not measured the timing of that and my interface only plays well at 2 or 3 periods/buffer.

[thoth_mcdonalds]

I'm hesitant to say my problem is definitely solved, but I'm going to follow up just in case this thread helps someone in the future with a similar problem. Here's the catch though, I don't know exactly what fixed the problem because I started over with a fresh install of Manjaro kde... But I did do a few things differently than I have in the past.

-Liquorix kernel! Never tried that before... I have my suspicions this could be the fix. I've installed AV Linux kernels on other Debian family members before, but since moving to Arch family I've only used the official kernels.

-Removed pulseaudio! Worked for AVL back in the day! I've been tinkering with Linux audio for a long time at this point, and learning has been slow, but one thing I'm confident about: I don't need pulse for what I do! I don't think this is likely the culprit, but it's possible!

-A Simple Bash startup script! I know this isn't the best practice for configuring a system, but I've followed the wiki where applicable to make changes permanent before. This time I wanted all of these commands in one place that I can # (comment out) a line or two for troubleshooting purposes and to observe errors. My script is very simple. It's just the last few parts of the pro audio arch wiki:

-adjusting RTC interrupt frequencies (I need to look into this more, I'm not doing this AT boot time so maybe it's not doing anything I just realized,)
-reducing swappiness,
-Increasing the maximum watches on files,
-maximizing the PCI latency timer of the PCI sound card and raising the latency timer of all other PCI peripherals (this I believe is one I've skipped before, having interpreted the wiki to say this is for "internal soundcards" but this time I set it for the FireWire connection and maybe this fixed it?) and finally, sleep for a few seconds and start Catia (which is my preferred way to start jack sessions these days, maybe second favorite to in command line.)

RESULTS:
with bulky KDE plasma running, wifi ON, I am able to run jack at 48000 sample rate & 64/3 buffer with 1.3 ms with ZERO xruns. I got a quick burst of 81 xruns when I started setbfree in Carla but that's not related to my previous problems and not how I prefer to run setbfree so I'm not too concerned. In fact, I don't think I've ever had it this good! 256/3 is the most reliable low latency setting I've been able to run before.

BACKGROUND:

I first noticed these symptoms (the predictable intervallic xruns) in an install of Arch, mint, multiple installs of Manjaro and most recently AV Linux. I had installed AVL for the first time in a few years because I was hoping a system fine tuned out of the box would fix the problem. I had no such luck. I love that distro and what Gmaq and Trulan do but I've been craving a lean machine, and can't ever seem to get purr-data or pd-l2ork installed correctly on Debian.

I've got a HP elitebook with a gen 2 i7 CPU, 8 gigs of RAM, and as I've stated before a MOTU 828mkii FireWire interface and a TI chipped FW card.