Subject: Re: [linux-audio-user] Is everyone sick of interrupts yet?
From: Mark Knecht (mknecht_AT_controlnet.com)
Date: Wed Sep 29 2004 - 01:05:47 EEST
Lee Revell wrote:
> On Tue, 2004-09-28 at 16:11, Mark Knecht wrote:
>
>>Lee Revell wrote:
>>
>>>I get no xruns at 32 (!) frames using 2.6 with the VP patches,
>>>and my soundcard shares an interrupt with USB:
>>>
>>
>>(Non-argumentive if it's unclear) Please stick a USB mouse on the USB
>>port that is shared and wiggle it madly while doing some of this. Can
>>you create an xrun?
>>
>
>
> No, this does not cause an xrun, because even though the USB interrupt
> handler interrupts the soundcard irq (and vice versa), it does not run
> for a significant fraction of the period time. Of course it's best to
> have the soundcard on an interrupt that is not shared. But whether that
> interrupt is #5 or #10 does not matter.
Great. Just checking. (You did *actually* do it, right?) ;-) On my
Gentoo kernels, if wiggle the mouse enough I can get an xrun or two.
Normal mouse usage doesn't, but then again we're talking about a single
xrun blowing a record which we don't want.
Under Windows XP, using Pro Tools on the same laptop, I can create many
'xrun' equivalents by moving the mouse at the wrong time, so I'm very
sinsitive to it.
Shared interrupts are only slightly worse than not shared. With shared
both devices have to be interrogated even if only one generated the
interrupt. this has to take longer. However, with good IRQ ahndler code
it should not be an issue. I think the Linux environment with open
source/peer review is far more likely to weed the problems out than the
closed source Windows world.
>
>
>>BTW - PIC or APIC interrupts?
>
>
> PIC (as in I only have irqs 0-15), but APIC works the same way.
Sure. I've worked on chipset design an have a bit of background there.
Never did the PIC, but it was part of the project.
>
> Lee
>
>
>
>
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