[LAU] eliminating xruns on 64-bit Arch ?

Dave Phillips dlphillips at woh.rr.com
Wed Dec 14 12:55:37 UTC 2011


I like my Arch system, but its rt performance is simply not so good as 
my old 64 Studio installation. 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

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

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

Please advise if other information is required.

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.



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