[mythtv-users] Mythbackend causing high load

Stuart Larson halcyon at obfus.com
Fri Jun 16 17:58:56 UTC 2006


I've seen this sort of behavior when recoding or transcoding (doesn't seem
to make a difference which) when my free space on drive was close to what
Myth is set to keep free - I have Myth set to keep 20G free, and when it
reached around 22-23G free, I started seeing this behavior (I'm running
reiserfs, so the xfs space-free thing shouldn't be an issue).  Not sure if
it would be related...  The recordings did work fine (PVR-250), but
watching while recording doesn't work very well.

> I'm seeing something very familiar, mythbackend uses about 100% CPU
> during a recording and though not always, I sometimes see IOBOUND errors
> in the log. I have transcode/commflag jobs set to run after midnight
> each day, and no other processes are using CPU while mythbackend is
> hogging it all.
>
> The weird thing is my box was running fine for a few months prior to a
> power outage. After the outage I booted up the box and I started to
> notice IVTV buffer overflows happening during every recording causing
> the load to spike up to 10+ during each recording. The recording was
> useless of course too. This was with IVTV 0.4.1 on a PVR-500.
>
> So I decided to upgrade to IVTV 0.4.5 to see if that solved the problem.
> Well, I no longer see IVTV buffer overflow messages in the log, but now
> mythbackend uses 100% CPU. I upgraded to the latest SVN snapshot of
> 019-fixes branch to see if that helped at all, but it didn't.
>
> So now mythbackend uses 100% CPU, the recordings seem to be working
> fine, but I can't watch any recordings while this is happening.
>
> I'm running an Athlon 2100 with kernel 2.6.14.
>
> Just last week I could have two recordings going at once, mythcomm flag
> running in real-time, and two frontends both watching recordings with no
> issues at all. Now one recording at a time and NOTHING else is all that
> can happen. :(
>
> Does anyone know what I can do to try and track this issue down?
>
> Thanks.
>
> On Fri, 2006-06-16 at 06:41 -0400, Jeff wrote:
>> On 6/15/06, Ryan Steffes <rbsteffes at gmail.com> wrote:
>>
>> > Do you, by any chance, have a slave to offload the transcode onto?
>> Try
>> > disabling transcode jobs on that backend, and see if it comes back.
>> Mine
>> > hasn't since then, even though it's a less than ideal fix.
>> >
>>
>> For the most part I don't do transcoding. I do have a 'transcode for
>> ipod'
>> job which seems to have gotten itself attached to every recording (it
>> was
>> only supposed to be one show) but I don't think its working at the
>> moment.
>>
>> I do commercial flagging though at the end of each show.
>>
>> I can try moving this to a slave backend.
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> --
> Mike Benoit <ipso at snappymail.ca>
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