[LAU] eliminating xruns on 64-bit Arch ?

[Jeremy Jongepier]

On 12/14/11 13:55, Dave Phillips wrote:
> Greetings,
>
> I like my Arch system, but its rt performance is simply not so good as
> my old 64 Studio installation.

Hello Dave,

Yeah, Arch is nice, I'm in the process of building up an Arch audio 
machine too.

  I think I have it optimized, but I wonder
> if there isn't more I could do to eradicate the occurrrence of xruns
> when recording with Ardour. Technical details follow.
>
> uname -a reports these facts  :
>
>      Linux BigBlack 3.0-ARCH #1 SMP PREEMPT x86_64 AMD Athlon(tm) 64
> Processor 3200+
>
> The relevant entries in /etc/security/limits.conf
>
>      @audio          -       rtprio          99
>      @audio          -       nice           -10
>      @audio          -       memlock         unlimited
>

You could check /etc/security/limits.d/99-audio-conf
I wonder though if both files exist if they don't conflict. What does 
ulimit -r -m output?

> I know about nice. IIRC these settings were default values.
>
> The hardware is an M-Audio Delta 66 system, with a separate preamp. Some
> relevant JACK (0.121.3) settings :
>
>      /usr/bin/jackd -P89 -t5000 -dalsa -dhw:0 -r48000 -p128 -n2 -Xseq
>

The seq driver can cause xruns. You can rule it out as a possible cause 
by using a2jmidid.

> I usually get two or three xruns per half-hour session, as compared to 0
> with 64 Studio. Btw, I'm not comparing the distros, just the performance
> stats. I have no interest in returning to older systems, but I have much
> interest in improving the ones I'm running now.
>
> This bothers me :
>
>      [dlphilp at BigBlack etc]$ cat /proc/interrupts
>                  CPU0
>         0:         50   IO-APIC-edge      timer
>         1:          4   IO-APIC-edge      i8042
>         7:          1   IO-APIC-edge      parport0
>         8:          2   IO-APIC-edge      rtc0
>         9:          0   IO-APIC-fasteoi   acpi
>        12:          6   IO-APIC-edge      i8042
>        14:          0   IO-APIC-edge      pata_amd
>        15:      27164   IO-APIC-edge      pata_amd
>        16:     788897   IO-APIC-fasteoi   ICE1712, nvidia <---- Ouch !!!
>        17:        144   IO-APIC-fasteoi   firewire_ohci
>        20:      49995   IO-APIC-fasteoi   ohci_hcd:usb2
>        21:      87877   IO-APIC-fasteoi   sata_nv
>        22:       2124   IO-APIC-fasteoi   sata_nv, hda_intel
>        23:      82436   IO-APIC-fasteoi   ehci_hcd:usb1, eth0
>
> Yep, that's my video card. Can I reassign the IRQ - preferably via
> software - for one of those devices ?

No, afaik only if your system supports MSI and it looks like it doesn't 
(unless you didn't post the whole output). But I'm no expert on this so 
I could be mistaken. You could try swapping ports for the ICE1712.

  If so, how and in what order ? I
> know about the rtirq script but there seems to little information
> regarding its use with a kernel such as mine (Rui ?).

With your current non-rt kernel you have to use the threadirqs kernel 
option. From then on you could install rtirq from AUR though that's not 
the most recent version so you might have to modify the PKGBUILD.

  Btw, I know that
> an updated kernel is available from pacman and will gladly install it if
> recommended.
>

The 3.0-rt kernel from AUR works amazingly well afaics, but I didn't 
stretch test it yet. Arch is nice but it lacks a whole bunch of plug-ins 
I need so have to take care of that first.

> Please advise if other information is required.
>

What DE are you using?

> Suggestions and recommendations are most welcome. However, before
> recommending an rt kernel please note that I need hardware accelerated
> 3D. Ditching the nVidia binary is not really an option yet, so any
> suggested kernel must get along with the nVidia driver.
>
> Best,
>
> dp

Best,

Jeremy