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SubjectRe: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0
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On Mon, 2004-10-25 at 22:11 -0700, Fernando Pablo Lopez-Lezcano wrote:
> On Mon, 2004-10-25 at 20:01, Lee Revell wrote:
> > On Mon, 2004-10-25 at 20:40 +0100, Rui Nuno Capela wrote:
> > > OTOH, jackd -R xruns are awfully back, even thought I (re)prioritize the
> > > relevant IRQ thread handlers to be always higher than jackd's.
> >
> > Actually they should be lower, except the soundcard. I was only able to
> > get the xrun free behavior of T3 by setting all IRQ threads except the
> > soundcard to SCHED_OTHER. Especially important was setting ksoftirqd to
> > SCHED_OTHER, this actually may have been the only one necessary.
> >
> > The relative priorities of jackd and the soundcard irq do not matter as
> > these two should never contend (aka they are never both runnable at the
> > same time).
>
> What happens when one is blessed with a laptop where everything is
> sharing an interrupt?
>
> $ cat /proc/interrupts
> CPU0
> 0: 2372239 XT-PIC timer 0/72239
> 1: 5362 XT-PIC i8042 0/5362
> 2: 0 XT-PIC cascade 0/0
> 8: 1 XT-PIC rtc 0/1
> 9: 616176 XT-PIC acpi, uhci_hcd, uhci_hcd, uhci_hcd,
> eth0, yenta, yenta, Intel 82801CA-ICH3, radeon@PCI:1:0:0 0/16176
> 11: 37 XT-PIC sonypi 0/35
> 12: 28392 XT-PIC i8042 0/28392
> 14: 21078 XT-PIC ide0 0/21078
> 15: 472 XT-PIC ide1 0/472

Ugh, why would _anyone_ design a laptop like that? You have 4
perfectly good interrupts that you are not using at all. Is it really
cheaper to put everything on the same irq? Does this work better under
Windows or something?

AFAIK there is nothing you can do - any other irq that fires on 9 will
mask out all the others until it completes.

I am increasingly convinced that the vast majority of laptops are
horribly broken and completely unsuitable for low latency audio work.

Lee

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