[mythtv-users] LiveTV glitches at program transitions (was Re: [mythtv] mythplayer.cpp query)

Russell Gower mythtv at thegowers.me.uk
Wed Mar 14 12:31:57 UTC 2012

>> I've taken this to the user list as it doesn't appear to be a development issue at this stage.
>> After my last post I started digging into the OpenFile() 4014ms issue, as Jens said it appears than the backend is having storage issues, I'm going to setup a separate combinded BE/FE test system for further analysis.
>> At this stage I believe the "Waited 0.2 seconds for data" are due to the frontend reading to close to the end of the file, if playback is paused for a few seconds they go away.
> May as well forward the request over there then...
> It looks like roughly 7.1 of that 7.6 seconds is sitting there waiting 
> for the data to get written to your filesystem. If the data isn't 
> available for the frontend to read it, then nothing you change in the 
> frontend is going to make the slightest bit of difference. We need to 
> see backend logs to see where the actual stall is.
> We also need to know more about how your system is actually configured. 
> Looking through the mailing list archives, you appear to be running 
> independent frontends, which means if you are reading off the 
> filesystem, you are reading over NFS. Is it possible your problem is 
> caused by nothing more than NFS caching issues that would be resolved by 
> merely not mounting those disks and letting MythTV stream its content 
> internally?

I only recently switched to using NFS, as the backend seems to stop supplying data over the internal protocol whilst the scheduler is running, I still had the program transition glitches then as well as additional glitches whenever the scheduler ran.

I no longer have the backend log, but from memory it was the threaded file writer waiting for a flush to finish

My current configuration is rather complicated (two node cluster, with DRBD shared storage etc), i'm in the process of setting up a dedicated system (with a conventional/separate OS/Media disk setup) to do further analysis on - I did had this problem to a lesser extent on my previous system that was a combined FE/BE (with dedicated raid1 disks for recordings) but that was running 0.23.

I currently believe this is a hardware issue, so I will pursue that avenue until I find otherwise.

Thanks to every one that has responded for the feed back, I'll report back my findings for posterity.


More information about the mythtv-users mailing list