[Jack-Devel] advice on xruns

[Hermann Meyer]

Am 28.07.19 um 04:05 schrieb liebrecht at grossmann-venter.com:
>
> Anyone have an in depth treatise on xruns and how to minimize them. By
> that I dont mean just adjusting the buffer size, I mean really getting
> into the gears of why xruns happen and how to potentially minimize them.
>
> Reason I ask is that I use jack on a live music basis amd it is
> crucial for me to get no more than 2.9ms latency.
> I can hear and feel every latency above above that.
>
> I am lucky with mixbus and jack on Linux to get 2.9ms with the
> occasional xrun every 2 minutes, but I want to see if I cannot
> eliminate them.
>
> Any advice or point to very relevant reference material will be
> appreciated.
>
> Thanks
>

What I found over the years is, there is no general rule for how to
optimize your system. It depend deeply on your hardware.

I could say what I need to do with my current machine, beside the usual
tweaks.

First I use a rt-kernel, then I add the following kernel parameters:

  threadirqs intel_pstate=disable processor.max_cstate=1
intel_idle.max_cstate=0 idle=poll

only with them I'm able to run smooth at low latency.

This is with a Quad Core model: Intel Core i5-7400 CPU.

Additional, when I need full power,  I increase the priority for my
sound-card thread, therefor I run as root:

chrt -f -p 95 $(ps -eLo pid,cmd | grep -i snd_hda] |sed q|  cut -d' ' -f3)

were snd_hda is m sound-card.

All this wasn't needed with my previous PC.


regards

hermann