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unhandled-irqs-switch-to-polling kills ivtv driver performance

 

 

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rda at rincon

Aug 18, 2012, 9:01 PM

Post #1 of 1 (1036 views)
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unhandled-irqs-switch-to-polling kills ivtv driver performance

Hi,

It looks like there's a pending kernel patch that's currently applied
to the Fedora kernels (since 3.4.4) that produces long pauses in
/dev/video0 output, making it unwatchable. Removing this patch from
the kernel restores performance (& no error messages). I've attached
the problematic patch for your inspection. The patch is trying to
overcome an issue that some people are experiencing with a particular
PCIe-PCI bridge. But there's something about the interrupt behavior
of the Hauppauge MCE150 card and ivtv that's giving it a false(?)
trigger. Or it could be that the problem doesn't affect the
H/W+driver, but the work-around does. In my situation the card is the
only thing behind this bridge. I only experience problems when the
attached patch is applied to the kernel.

I've posted more details at the Fedora bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=845211
(ASM108x) "IRQ might be stuck. Polling" causes dropouts on PCI DVB card

I'm posting here to give you a heads-up to a situation that may become
more prevalent if this patch gets in to the mainstream kernel. And
hopefully as ivtv developers you might be able to provide to some input
improve this patch so it doesn't impact ivtv performance.

Respectfully,
-Bob Arendt
Attachments: unhandled-irqs-switch-to-polling.patch (8.82 KB)

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