Re: [LAU] Too many xruns

On Thu, 06 Sep 2012 10:02:11 -0700
Kevin Cosgrove <kevinc@email-addr-hidden> wrote:

>
> On 6 September 2012 at 8:43, Kevin Cosgrove <kevinc@email-addr-hidden>
> wrote:
>
> > > >> cat /proc/interrupts
> > > >
> > > > Xrunning system says:
> > > >
> > > > CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 CPU6 CPU7
> > > > 16: 56322 0 0 0 0 0 0 0
> > > > IO-APIC-fasteoi ahci, ehci_hcd:usb1, firewire_ohci,
> > > > snd_ice1712, nvidia
> > >
> > > That would give me xruns too.
> >
> > OK. I see it now. I've never had to fight the interrupt problem
> > before.
> >
> > > (if you can) See if you can set IRQ in the bios for that slot
> > > to something else if there is only one.
> >
> > I'll look at the manual for my MB and see what I can do.
>
> I did a search for "irq" on this website
>
> http://www.manualowl.com/m/Asus/P8Z68-DELUXE%2FGEN3/Manual/263040?page=91
>
> and found a page (2-14) that lists the (non-alterable???) IRQ
> assignments for my motherboard. The good news is that one of
> the legacy PCI slots has less stuff on the IRQ. The bad news
> is that one of the PCI slots has lots of stuff on that IRQ.
>
> Looking at IRQ 16 above, my nVidia shows up. It's PCiE x16,
> and my motherboard seems to have 3 of those slots, with one slot
> being on a different IRQ. I suspect moving the video card might
> help, right?
>
> Basically, my strategy would be to disable drivers I don't use.
> For instance, I don't have any firewire gear. Next, I'd move
> anything I could to a slot using a different IRQ than the one
> I want to reserve for the Delta 1010. Seem like a good plan?

FWIW, I have a similar system with an Asus P8Z68-V PRO GEN3 + Intel
i7-2600k CPU, I have an rme multiface PCI card in a slot that gives it
IRQ 18 all to itself. The only irq priority manipulation I do is to
run chrt -f -p 98 `pgrep irq/18-snd_hdsp` from /etc/rc.local.

I also have the system running with the default ondemand governor.

I don't use an external NVIDIA card as the built in HD3000 GPU works
a treat for low latency audio even with a full KDE install with
compositing kwin. If I did use a NVIDIA card I would most likely use
the nouveau driver that lately has become very good for low latency
audio.

Kernel is 3.4.9-rt17. Running cyclictest -m -Sp99 -i100 -d0 shows me
kernel scheduling latencies of well under 0.1ms no matter how hard i
push the system, and that is with the ondemand governor...

All in all very pleased with this system, and I think you will be
too if you move the soundcard to another slot, having less stuff on it.

Another tip, if you have to use a slot that shares IRQs, then you have
to raise the priority of all the soft interrupt threads that share
the IRQ with the soundcard, otherwise you will get a lot of xruns.

---

   Joakim
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Received on Fri Sep 7 12:15:03 2012