Re: [linux-audio-user] rme hdsp latency and irq settings

On Mon, 1 May 2006 03:08:40 -0700
"Rich E" <reakinator@email-addr-hidden> wrote:

> I've been running a RME hdsp multiface2 with pci on the PlanetCCRMA
> low latency kernel for a couple months now, and while it runs nice, I
> can't get the latency in Pd below about 20ms. If I set anything
> lower, there are dropouts. I've messed around with the Pd settings a
> bit, but I haven't touched any system settings because I'm confused by
> the stats of my soundcard. lspci -v tells me the hdsp card is on irq
> 187 and it has 255ms latency. According to all the documentation I
> have seen (which is all at least a couple years old, most the time
> around 2000), neither of these numbers should be possible. I think
> the low latency kernel, with "realtime preemption patch by Ingo
> Molnar", is messing with these, but I really don't know.
>
> Does anyone know anything about what the hdsp's irq and latency
> settings should be on a realtime linux system?

Forget what lspci tells you about latency. It's not a millisecond
number. It should actually not interest you in any way. Anyways, i
suppose you use a system with a local APIC. That explains the high
interrupt numbers. Contrary to the previous XT-PIC older systems had,
and which assigned irq numbers in the range of 0-15 [with some
oddnesses], the local APIC uses a very different scheme. The old XT-PIC
scheme was severely limited due to the small number of irq's available
for devices.

Anyways, you might want to read around on the webpage in my signature.
It gives some clues on how to setup a system with a -rt kernel.

To inspect your priority setup i'd recommend htop which can sort for
priority.

Regards,
Flo

P.S.: I don't know how well jack'ified Pd is. I never tried it. Maybe it
simply sucks ;) Do you use it with jack at all? If you do run it with
the ALSA backend, does it have a way to set its priority?

-- 
Palimm Palimm!
http://tapas.affenbande.org