[mythtv-users] 0.25 lookup metadata as part of jobqueue?

Raymond Wagner raymond at wagnerrp.com
Sun Mar 11 15:43:16 UTC 2012


On 3/11/2012 08:03, Scott & Nicole Harris wrote:
> It would also be nice to set a different max jobs per job type.  i.e. Allow
> 4 commercial flag jobs but only 1 transcode job at a time.

That's still far from optimal.  Commercial detection can run in realtime 
behind a recording, or at full speed behind a recording.  At full speed, 
it will fairly efficiency balance over two cores, meaning those four 
jobs would saturate a dual socket, quad core server.  In realtime, all 
of those commercial detection runs will sit idle for the first ten 
minutes, waiting for enough data to do icon detection, and then catch up 
as fast as they can to the in-progress recording, again saturating that 
high end server.  Depending on how many simultaneous recordings you 
have, you may not have a choice of which mode the jobs are going to run in.

With transcoding, you can either do a CPU intensive transcode, or a disk 
intensive lossless transcode.  Mythtranscode itself is primarily single 
threaded due to its available codecs, so you would want to run one job 
for each core when operating lossily.  On the other hand, you would want 
to run one job per available disk, and avoid conflicts with in-progress 
recordings, when operating losslessly.

Then you get into issues with how do you mix multiple types of jobs.  
Would you allow four commercial detection jobs and one transcoding job 
to run at the same time?  Do different types of jobs block each other?  
Do you have some sort of sliding ratio between the two?  You start 
adding options for manual tuning of that behavior and suddenly you have 
a giant, unwieldy transform table that most people don't know about and 
no one actually wants to touch.  See the weighting options available in 
the disk scheduler as a prime example of this.  Any usable change from 
the current behavior would be to implement some form of heuristic 
scheduler, that tracked what kind of resources were likely to be used 
for different tasks against different types of recordings, and adjusted 
accordingly.


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