linuxaudio.org

On 7 September 2012 at 10:17, Joakim Hernberg  wrote:
> On Thu, 06 Sep 2012 10:02:11 -0700

quoted text
> Kevin Cosgrove  wrote:

>

> >

> > On 6 September 2012 at 8:43, Kevin Cosgrove

> > 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=9...

> >

> > 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,

That is VERY similar, and gives me hope.
> I have an rme multiface PCI card in a slot that gives it

quoted text
> 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.

Nice.  Again, the IRQ isolation theme.
> I don't use an external NVIDIA card as the built in HD3000 GPU works

quoted text
> 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.

The nouveau driver didn't do so well with my dual monitors.  Ardour

is _great_ with the mixer window on one monitor and the editor window

on the other.
> Kernel is 3.4.9-rt17.  Running cyclictest -m -Sp99 -i100 -d0 shows me

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> kernel scheduling latencies of well under 0.1ms no matter how hard i

> push the system, and that is with the ondemand governor...

Nice.
> All in all very pleased with this system, and I think you will be

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> 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.

More with the IRQ isolation and prioritization theme.  I haven't had

time to play with that.  But, it's next on my list after I get done

with a recording project using the other system.
Thanks!!
--

Kevin
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