Re: [linux-audio-user] IRQ sharing

On Sun, 05 Mar 2006 02:02:18 -0800
Florin Andrei <florin@email-addr-hidden> wrote:

> On Sun, 2006-03-05 at 03:35 -0500, Eric Dantan Rzewnicki wrote:
> > Old school Linux Audio lore held that it was bad to let your audio card
> > share an IRQ with anything else. Is this a myth, or still good solid
> > practical advice?
>
> It might still have some influence, but nowadays the typical hardware is
> so fast, it doesn't matter like it used to.
>
> I'm getting pretty good latency with no xruns when running jackd with
> real-time priority, despite INT 5 being crowded like hell:

Hi,

this might work out in the most situations, but of course it depends on
what kind of devices share the IRQ. Imagine a situation where the ide
controllers and the sound interface are on the same irq. Now, if you do
heavy disk I/O there's a very real chance of the audio operation getting
disturbed, especially at low latency settings.

If the ide controllers and the audio interface were on different IRQ's
one could use the irq handler thread priorities of a -rt kernel to
practically guarantee xrun free operation even under heavy disk load
(simply by giving jack and the audio irq higher prios than the ide
controller irqs).

With a shared IRQ this option is not availale anymore. So, depending on
what you want from your box, non shared IRQs can make sense and can have
real advantages.

Flo

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