[arch-proaudio] JACK 1: extreme CPU usage (since update from 5.0 kernel)

[Jeanette C.]

Hey hey everyone,
JACK has long had a habit of grabbing a lot of CPU time, even in idel mode, 
getting to 100% (one of four cores) and raising the CPU from 800MHz to 3GHz. 
But it usually took some time. Restarting the JACK daemon resolved the issue 
for some time.

Since the update from the 5.0.x kernel to first a 5.1(?) (last Sunday) and now 
5.2.5 has incrased the issue. JACK quickly starts grabbing lots of CPU, 
heating up the system (and waisting energy).

This gets to a point where I can't change terminals. Only when I stop JACK, 
the system will react to an already pressed alt+fN command, as if it was 
stored in a bugffer, but couldn't be reacted upon.

The keystrokes are read immediately, as verified by showkey, the problem is 
JACK as verified, by always getting a prompt from tty1 after shutting it down.

I have set the kernel commandline parameter audit=0 .

Another suggestion recommended trying something with spectre mitigation. There 
was mention of a few kernel parameters and possible security risks, which went 
over my head.

Can someone please help me through this? Hints, tips, maybe similar 
experiences and good solutions?

I have run:
realTimeConfigQuickScan
which aggreed with everything except that my kernel isn't real lowlatency. 
It's the standard pacman kernel. And it didn't like the schedutil governor, 
which I change to performance, when I'm recording.

More info?
CPU: AMD Athlon(tm) II X4 640 Processor (/proc/cpuinfo)
   quadcore with up to 3GHz
4GB of RAM (mostly no issues at all)
no GUI
Soundcard: twl M-Audio Delta 1010LT sync'ed by SP/DIF and bundled into one 
device through ALSA through multi device type.

Any help is appreciated!

Thanks you and best wishes,

Jeanette

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