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

[David Runge]

On 2019-08-06 13:51:42 (+0200), Jeanette C. wrote:
> How do I check my soundcards realtime priority. iotop gives a kind of
> RTprio as something like be/4, the manual is unclear on that
> classification. Well, they don't explain it. :)
If you install and setup rtirq (that's quite straight forward) with a
realtime kernel, its status output will show you just that: `rtirq status`

Else, if you require more output, you can try something like:

```
ps -eo pid,class,rtprio,ni,pri,pcpu,stat,comm --sort -rtprio
```
(That's actually what's being called within rtirq as part of the status
call.)

Note, that rtirq doesn't make much sense (or just won't have the same
effect), when not using a realtime kernel (or the 'threadirqs' kernel
parameter [1] - which is the default on linux-rt{,-lts}, but can be
activated for the vanilla kernel as well - for that matter).

While you can set very specific IRQs (based on the names in the most
right column in `/proc/interrupts`), rtirq also allows for more general
approaches (e.g. 'usb' for all USB devices, or 'snd' for all PCI based
internal audio devices), when setting the priorities in its
configuration file.

Best,
David

P.S.: Closing, it of course also makes sense to monitor your jackd
service closely, by attaching to its journal (e.g. `journalctl --user -f
-u myjackd.service`) and potentially momentarily increasing its
verbosity (for debugging, if you think there's still something wrong).

[1] https://www.kernel.org/doc/html/v4.14/admin-guide/kernel-parameters.html

-- 
https://sleepmap.de
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