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RE: [Xen-users] xen and mythbackend?

To: "Gordon McLellan" <gordonthree@xxxxxxxxx>
Subject: RE: [Xen-users] xen and mythbackend?
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Wed, 26 Mar 2008 11:12:02 +1100
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Thread-topic: [Xen-users] xen and mythbackend?
> 
> The crashes seem to be DMA related ... but I'm not sure what the
> "trigger" is - it's not high disk load or high cpu load... perhaps low
> memory is the cause?
> 
> The card (pvr500) is actually two codecs sharing one pci interface ...
> both will be capturing video, and then the capture output stops,
> usually on the second codec only (ivtv1).  All that is reported in the
> logs is DMA timeout ivtv1.
> 
> Sometimes the system will run like that for days, without me noticing
> any degradation in other services, other times, it will crash quick,
> tying up hard drives like there is some sort of bus contention,
> leaving me no choice but to hit the reset button    On a soft crash
> (one that doesn't kill the box) I've tried to "recover" without
> rebooting by unloading the kernel module (rmmod ivtv) and loading it
> again.  This results in a segfault logged by the kernel, and things go
> down hill from there.  The segfault cites being unable to allocate DMA
> memory to the driver, again, usually for only the second codec
> (ivtv1).

Those sort of symptoms make me thing that even under Xen, the card will
still crash your PCI bus, crashing not only that DomU but also Dom0 and
therefore the whole box. If you can test it easily then go for it, but
I'd suggest putting it on a box on it's own with a watchdog timer to
detect failures.

Or just get another DVB card, although I understand that the pvr500 is a
fairly nice piece of equipment.
 
James



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