I say hallo for Harry ! ;)

F: I have some troubles - read xruns - with this setup:

H: There's a lot more to removing Xruns from a system than just the kernel and JACK settings (although they are very important :)

F: actually I know realTimeConfigQuickScan, so my output looks:

[paum@bookes ~]$ realTimeConfigQuickScan

== GUI-enabled checks ==

Checking if you are root... no - good

Checking filesystem 'noatime' parameter... 3.6.11 kernel - good

(relatime is default since 2.6.30)

Checking CPU Governors... CPU 0: 'performance' CPU 1: 'performance' CPU 2: 'performance' CPU 3: 'performance' - good

Checking swappiness... 10 - good

Checking for resource-intensive background processes... none found - good

Checking checking sysctl inotify max_user_watches... >= 524288 - good

Checking access to the high precision event timer... readable - good

Checking access to the real-time clock... readable - good

Checking whether you're in the 'audio' group... yes - good

Checking for multiple 'audio' groups... no - good

Checking the ability to prioritize processes with chrt... yes - good

Checking kernel support for high resolution timers... found - good

Kernel with Real-Time Preemption... not found - not good

Kernel without real-time capabilities found

For more information, see http://wiki.linuxmusicians.com/doku.php?id=system_configuration#installing_a_real-time_kernel

Checking if kernel system timer is set to 1000 hz... found - good

Checking kernel support for tickless timer... found - good

== Other checks ==

Checking filesystem types... ok.

ok.

** Set $SOUND_CARD_IRQ to the IRQ of your soundcard to enable more checks.

Find your sound card's IRQ by looking at '/proc/interrupts' and lspci.

[paum@bookes ~]$

and I dont understand two things:

Kernel with Real-Time Preemption... not found - not good

Kernel without real-time capabilities found

BUT

[paum@bookes ~]$ uname -a

Linux bookes 3.6.11-rt33-1-rt #1 SMP PREEMPT RT Sun Apr 28 12:18:40 CEST 2013 x86_64 GNU/Linux

[paum@bookes ~]$

and the second, how to:

** Set $SOUND_CARD_IRQ to the IRQ of your soundcard to enable more checks.

Find your sound card's IRQ by looking at '/proc/interrupts' and lspci.

H: Known things that need to be done:
-Interrupt requests of your hardware must be prioritized (rtirq script helps here)

F: my system says:

rtirq.service loaded active exited Realtime IRQ thread system tuning

H: -Interrupt thread handlers (on RT kernel) must be prioritized

F: how to ?

H: -Thread priorities must be checked for JACK itself

F: How to ?

H: Some other things to look into are:
-CPU scaling (causes Xruns here, although others say it works fine)
-WiFi (must be disabled here: "iwconfig wlan0 txpower off", not just disconnected)

-Graphics chip drivers (I'm using a standard xf86-video driver for my ATI HD2400XT)

F: CPU scaling seems good:

Checking CPU Governors... CPU 0: 'performance' CPU 1: 'performance' CPU 2: 'performance' CPU 3: 'performance' - good

WiFi - thats pity, because I often use my phone as controller (TouchOSC)

Graphics - Nvidia - I am using noveau driver

H: That's a good start anyway: If I find some time, I'll write a quick post on tuning an Arch system for maximum low-lat RT performance.

F: appreciated ;)

F: My aim is to get as low latency as possible.
H :Please specify... How low is low :D I've achieved 0.3ms at 96kHz, running a CPU stress test on each core without Xruns, so I'm pretty happy with that... since the hardware (Echo Indigo DJ PCMCIA) can't handle any lower!

F: oh, great !. it could be an ideal for me. I use various acoustic instruments for live playing, so yes I am talking about less than 4ms

F: but none of them was without xruns when running:
pd - plugins - ardour

H: PD is a bit of a xrun hog on my machine here: not bashing PD, I probably don't have it set up with ideally. But perhaps try running eg Ardour on its own for testing purposes? Or another simple app which isn't as dependent on the "patch" that's loaded..?

HTH, -Harry

fero