[mythtv-users] Live TV playback frustration

[Warpme]

On 8/19/12 1:54 PM, Adrian Saul wrote:
> On 19/08/2012 2:37 AM, Adrian Saul wrote:
>
>> There is some lag on the playback startup and that occasionally 
>> affects the other frontend too - so far the only thing in the logs is 
>> time taking to do "SyncPositionMap" - which is odd because following 
>> the code and doing SQL behind the query completes instantly when I 
>> test it but in the logs I can see multiple instances where it takes 
>> 13 seconds or more.   Might take a closer look at what the database 
>> is doing because the code shows nothing else that would block this.
>>
> So - for all my confidence in my infrastructure I took a look at the 
> database to see what might cause this query to take so long. Any time 
> I manually tested it, the performance was fine - near instant 
> response.  When I took a look at the tables I realised some things:
>
> - I have 1500+ recordings
> - Those recordings have 9.1M rows in the "recordedseek" table which is 
> queried by SyncPositionMap.
> - Those tables were all on MyISAM tables from when I exported the 
> database myself from Linux to Solaris.... doh
>
> So while I could not reproduce it, I took a guess that table locking 
> on a 9.1M row table was not going to be great under MyISAM, and 
> started converting most of my tables to InnoDB and in the process 
> tweaked the ZFS setup underneath it to match recommendations for 
> InnoDB.   I had the memory for it so I also setup the database with a 
> 512M InnoDB cache. That seemed to resolve the lagging start issue on 
> the second frontend and also seems to make things a lot snappier in 
> general.
>
> I also revisited my NFS setup.  To try and fix the second frontend 
> being unable to change channels (loses the jump buffer) I tried 
> setting actimeo=0, but that just caused LiveTV to stutter and fail 
> constantly.   In desperation I switched back to NFSv4 with no special 
> tuning and it all just started working properly.
>
> So, thanks for the all the suggestions. Seems like it was my setup.
>
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Adrian,
I understand You are using file sharing option for FE access to 
recordings/LiveTV.
I think You can try myth stream protocol instead of NFS.
You can do this simply by not sharing /myth/tv (mythtv will discover and 
auto switch to use myth protocol).
I'm using setup based on myth protocol for 3 diskless FEs (ION) + MAC FE 
with great success (any combination play recordings, LiveTV, etc)
No any lags with playback starting. Also LiveTV has as-should-be 
stability for me.

-br

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