Re: [Xen-users] xen and mythbackend?

["Gordon McLellan" <gordonthree@xxxxxxxxx>]

James (and list),

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).

This problem (or ones similar to it) is documented various places, but
no one has found a concrete cause or a solution.  Some suggest the
card is defective, but I'm thinking it is a software problem.   Before
Centos 5 came along with the 2.6.18 kernel, I ran the card under
Centos 4 with a (more or less) vanilla 2.6.20 kernel and had no
problems.  My guess is the ivtv drivers do not like the taste of a
redhat kernel.  Problem there was I felt a bit "naked" running a
vanilla kernel, and having to update it manually now and again also
grew tiresome.

I was hoping to virtualize the myth backend server so I could try
different flavors of linux, or run a vanilla kernel without having to
worry about keeping it current, as long as it works.


Gordon


On Tue, Mar 25, 2008 at 7:28 PM, James Harper
<james.harper@xxxxxxxxxxxxxxxx> wrote:
> > I'm building a new server for
>  > home and would like to virtualize myth if possible, since it likes to
>  > crash often, and usually takes the rest of linux with it. (crashes are
>  > related to ivtv drivers for the card).
>
>  Can't help you much, except that depending on the crash you are seeing,
>  xen may not be the answer to your problems...
>
>  What is the nature of your crashes?
>
>  James
>

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