7 Sep
2012
7 Sep
'12
10:18 a.m.
On Thu, 06 Sep 2012 10:02:11 -0700
Kevin Cosgrove <kevinc(a)cosgroves.us> wrote:
On 6 September 2012 at 8:43, Kevin Cosgrove <kevinc(a)cosgroves.us>
wrote:
OK. I see it now. I've never had to fight the interrupt problem
before.
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
> 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. (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.