[LAU] XanMod kernel

Roger gurusonic at gmail.com
Sat Jun 6 13:59:10 CEST 2020

On 6/6/20 8:35 pm, Jeremy Jongepier wrote:
> On 04/06/2020 11:25, nik at parkellipsen.de wrote:
>> Hmm I never felt any advantage using RT kernels, either, at least in the recent
>> years, so I wonder if they still have any advantage in 2020 ? And that's not a rhetorical
>> question, I really wonder what contemporary use cases for RT kernels in the audio world are.
>> I feel like these kernel-tuning approaches date back to times when desktop responsiveness
>> etc. were much more serious issues. Might be wrong here, of course.
> I concur that with some applications a RT kernel can be beneficial,
> think of running soft-synths or samplers at very low latencies (with
> buffer sizes below 128 samples) or for use with dedicated devices like
> MOD Duo, Zynthian and that TC Electronics device that passed here a
> couple of days ago.
> When using a DAW the benefits of using a RT kernel are less clear. Out
> of curiosity I did some small tests with a 20 track Mixbus32C session
> using ALSA at 128 samples buffer size, 3 periods and 48kHz sample rate
> and with both a home-rolled 5.6.14-rt7 and a stock Ubuntu
> 5.3.0-lowlatency kernels the number of xruns stays below 5. Session is
> about 3 minutes long and consists of a DrumGizmo Crocell kit and some
> guitars running Guitarix, all real-time (so no bounced tracks). This is
> on a somewhat older notebook with one of the first Intel i7 iterations,
> a tweaked Ubuntu 18.04 (no hyper-threading, no Bluetooth, no Wifi) and a
> decent USB sound card sitting on its own USB bus.
> Thought I'd share it, maybe it helps people to decide if they should try
> a RT kernel or not. For all a RT kernel is not a panacea that
> miraculously solves your xrun problems, those problems could lie
> elsewhere as already pointed out by others. Additionally to the Ardour
> manual link I'd like to point to
> https://wiki.linuxaudio.org/wiki/system_configuration. Even though it's
> a somewhat older article it still contains valuable information that
> could help pinpointing the cause of xruns.
> Best,
> Jeremy

That wiki article is a goldmine of good advice even if a couple of 
things are outdated. Raboof's realTimeConfigQuickScan contains some 
links back to it. The QuickScan script has recently been updated so is 
100% useful again.

I started this thread so will report progress. I managed to compile 
XanMod but it didn't perform well for me with a flood of xruns, probably 
user error. Curiously the AVL lowlatency kernel didn't either which 
doesn't seem right. So I ended up back with Liquorix which I've been 
using all along, getting occasional random xruns which is what I was 
trying to eliminate.

I just read some lengthy threads on Liquorix forum where its developer 
damentz mentioned it is not actually targeted at low latency audio. It 
is configured with CONFIG_HZ=250 and I'm wondering would it be worth 
recompiling it with CONFIG_HZ=1000 as recommended several times in the 
wiki article?


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