Old 07-27-2020, 08:32 AM   #1
Soli Deo Gloria
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Default Realtime priorities in Linux

I'm almost done with my list of tweaks for the Newbie's Summary thread. There is one thing left to understand. I could have bumped this thread https://forum.cockos.com/showthread.php?t=238155 ,but I want to focus on some specific questions this time, and I 'm on Xubuntu now (tweaked from scratch, as opposed to Ubuntu Studio which has some pre-built tweaks), so...


1) How much RT priority should be given with the Rtirq script to the soundcard?

As I understand it, I have a USB Komplete Audio 6, so in /etc/default/rtirq , I put the following :


RTIRQ_NAME_LIST="xhci_hcd" (I understand that this is for USB devices; correct me if I'm wrong).

RTIRQ_RESET_ALL=1 [EDIT] This is probably better if set to 0 (!!!)


which shows the following output with $ sudo /etc/init.d/rtirq status :





So, is 95 a good RT priority for the soundcard? Is it correctly assigned?


2) How much RT prioirty should be assigned to Reaper? The Audio Device section of the Preferences, with ALSA, shows "40" as a recommended value... Is that the correct in this case? Should I assing 95 to the soundcard and 40 to Reaper? Or 95 to the soundcard and 90 to Reaper?


3) I'm generally using ALSA, but, when resorting to JACK, how much RT value should be assigned with QJackctl or Cadence? 80? Another value?

4) Is there anything else that should be set with Rtirq?



Thanks in advance!

Last edited by Soli Deo Gloria; 07-27-2020 at 08:44 PM.
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Old 07-27-2020, 09:38 AM   #2
Glennbo
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I did not do the line,

RTIRQ_RESET_ALL=1

I might try it on my new computer build later this week though, as I will likely be starting from scratch unless Linux is happy from one boot to the next with an entirely different computer with entirely different brand of CPU and chipset.

So mine currently comes back with this (IRQ 16 is my USB audio)

Code:
  PID CLS RTPRIO  NI PRI %CPU STAT COMMAND	
  103 FF      95   - 135  0.0 S    irq/16-ehci_hcd	
  104 FF      94   - 134  0.0 S    irq/23-ehci_hcd	
   48 FF      50   -  90  0.0 S    irq/9-acpi	
  106 FF      50   -  90  0.0 S    irq/12-i8042	
  107 FF      50   -  90  0.0 S    irq/1-i8042	
  108 FF      50   -  90  0.0 S    irq/8-rtc0	
  185 FF      50   -  90  0.0 S    irq/19-pata_jmi	
  192 FF      50   -  90  0.0 S    irq/29-ahci[000	
  211 FF      50   -  90  0.0 S    irq/18-ahci[000	
  527 FF      50   -  90  0.0 S    irq/17-snd_hda_	
  528 FF      50   -  90  0.0 S    irq/31-snd_hda_	
  962 FF      50   -  90  0.0 S    irq/30-enp2s0	
 1015 FF      50   -  90  0.3 S    irq/32-nvidia	
 1016 FF      49   -  89  0.0 S    irq/32-s-nvidia
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Old 07-27-2020, 08:36 PM   #3
Soli Deo Gloria
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Quote:
Originally Posted by Glennbo View Post
I did not do the line,

RTIRQ_RESET_ALL=1

Hmmm, now that I'm working with this setting, I see that I have way better performance with that line set to 0, and an output similar to yours... I'll try to confirm it tomorrow, but maybe it's better to leave it at 0.

Last edited by Soli Deo Gloria; 07-27-2020 at 08:43 PM.
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