[LAU] Issue with the priority of the sound cards using rtirq

Fernando Lopez-Lezcano nando at ccrma.Stanford.EDU
Tue May 1 18:32:00 UTC 2012

On 05/01/2012 04:17 AM, Jeremy Jongepier wrote:
> On 05/01/12 12:09, Ralf Mardorf wrote:
>> Jeremy, the bad is, that I don't have another PCIe x1 slot:(.
> Ah bummer :(
>>> > In my experience, restarting the script tries to raise the priorities
>>> > of the threads in RTIRQ_NAME_LIST, but the ones which are already
>>> > raised aren't lowered even if you leave them out of the list.
>>> >
>>> > Try rebooting the computer.
>>> >
>>> > Cheers, Pablo
>> *reboot*
>> The reboot doesn't improve anything:(.
> So the output of /etc/init.d/rtirq status is the same as in the other
> mail? That's really weird. The only thing I can think of is that
> something else (another script?) is prioritizing stuff too (like the
> nvidia and ohci_hcd processes).

(I don't seem to find the start of the thread in my mailbox)

ohci_hcd is there is you specify usb in the list of priorities rtirq 
needs to raise. And nvidia is there probably because it shares an 
interrupt with a real soundcard. Rtirq does not raise the priority of 
only the soundcard, but everything that uses the interrupt that the 
soundcard uses.

AFAIK it is not possible (or simple) to raise _just_ the soundcard as it 
is impossible to know which irq process corresponds to a soundcard (and 
which one does not). That is because the labeling of the irq process 
names in the ps listing is arbitrary. At least that is what I remember 
seeing last I looked at this issue. You can of course manually lower the 
priorities of non-soundcard irq processes with chrt.

-- Fernando

>The steps between the priorities
> strengthens my suspicion, it should be 5 but some processes do not get a
> prio that can be divided by 5 (like nvidia which has prio 82). No one on
> the Ubuntu Studio list encountered the same issue? Maybe Ubuntu (or
> Ubuntu Studio) prioritizes processes somewhere else.

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