thank you for looking into this.
jack has a realtime priority, that is why one has to edit limits.conf and use the audio group and stuff like that. I had thought that the realtime-kernel would priorize threads with a realtime-priority even higher. So I understand now that it is still important do turn off non-audio stuff.
I have a pretty new notebook (Lenovo l380 yoga), the intention was to have a computer I can do everything with (I teach math, music and computer science, so there is quite a lot i do with my notebook).
I'm afraid that things get mixed up now with my other thread (about bad performance when power-plug is in), so I'll answer here to both, as you asked how things are going.
KDE runs really fast on my pc, and KDE is no longer "bloated" or what others still sometimes write about it. I really like it, especially dolphin, the file-manager. So I really do not intend to stop using kde for my everyday work, but I might use something else for audio stuff, if needed.
One problem was the system doing "behind-the-scene"-stuff. I guess with turning off networking and stopping file-indexing, this was widely fixed, I am not 100% sure that it is totally fixed.
The much bigger problem is that this notebook uses an "U"-processor. The general advice is to "turn off power-saving", but this is not so easy with modern processors. Simply using "performance" governor with cpupower ensures that the cpu is running at it's highest frequency while idle (!). As soon as it is really used, the frequency will be dropping, because the cpu cannot keep the highest turbo-boost frequency, it is not designed for that.
So I downloaded prime95 to make a stress test and see what frequency can be permanently kept up with my processor (intel Core i5-8250U, a very common processor in notebooks with 4 real cores). I watched the frequency with i7z, a very detailled tool designed for intel-processors. I saw that the frequency that can be kept up permanently is 1.8GHz. So now I use the following script:
Code: Select all
#!/bin/bash
for i in {4..7}; do
echo "Disabling logical HT core $i."
echo 0 > /sys/devices/system/cpu/cpu${i}/online;
done
cpupower frequency-set -u 1800MHz
cpupower frequency-set -d 1800MHz
This way I get good performance (though not as good as wich cpupower frequency-set -g performance as long as the machine is cool) and very stable. I still get an xrun every 5 or 15 minutes or so.
The last problem is that I use cpu-intensive stuff (pianoteq, guitarix) and need low-latency for live playing.
To get rid of the last xruns I plan the following two things:
- try turing pianoteq to 24kHz sample rate, I'll have to ask people if they hear a difference (I don't)
- disable processor c-states
I wonder if the second point is necessary, as the cores won't get much sleep when I do music anyway. But if one does accidently, this might provoke the occasional xrun.
All in all a low-voltage cpu seems to be ill-suited for audio. I had not realized this when I bought it. I have an old core2-quad desktop standing around which is more reliable in terms of xruns (but less powerful, of course).
Any hints for me? Sorry for the long post.
Andreas