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

Kevin Kuphal kkuphal at gmail.com
Wed Mar 14 13:18:48 UTC 2012


On Wed, Mar 14, 2012 at 7:31 AM, Russell Gower <mythtv at thegowers.me.uk>wrote:

> >>>
> >> 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.
>

The best thing I did for my system was put the database and /var logging on
a different spindle than recordings.  I have had zero disk issues since
doing this.  The amount of difference this can make is significant.

Kevin
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