[mythtv-users] Lengthy delay watching recordings

[Rich West]

On 05/22/2012 03:46 PM, Michael T. Dean wrote:
> On 05/22/2012 02:19 PM, Rich West wrote:
>> I noticed that going to 0.25 about a month back that the delay to start
>> playing an HD video had increased substantially and was curious as to
>> what might be the cause.
>>
>> As I looked further, I realized that it is with all video, but HD
>> content appears to be the most obvious offender.  It can take up to 31
>> seconds from the moment the user selects the video to play before it
>> actually starts playing.
>>
>> My backend system is well used, but from the graphs I have, it's not
>> hurting with CPU or memory.  Network to the frontends are all hardwired
>> (backend is gig, frontends are 100 meg).  From a utilization
>> perspective, the drives on the backend server are always hovering at
>> around 85% utilization, which is good, and the general I/O on the drives
>> is not such that it would cause a negative impact.
>>
>> I am using commercial detection, so I do suspect that there is some form
>> of buffering going on, but for 31 seconds?  No network errors on the
>> switch or the interface for the frontend or the backend.    CPU
>> utilization on the frontend is low.. basically idle.
>>
>> I'm just wondering if there is a particular place within MythTV to look
>> (for example, I recently found that it was recommended that "quick
>> tuning" should be enabled for the hdhomerun)..
>>
>
> /me guesses you have MySQL data on a file system with barriers enabled.
>
> Mike

Thanks, Mike.  You are right.. In my case, it was probably pre-0.25
since I had rebuilt the system after a failed root drive, and, as part
of the rebuild, went with a clean install of Fedora 16 (restoring my DB
from a nightly backup) which defaults to ext4.

The ext4 "barrier" is somewhat controversial in its functionality. I'll
tinker around with it and see if it helps. :)

-Rich