[mythtv-users] Commflagging X 4 = CPU ?

Craig Treleaven ctreleaven at cogeco.ca
Sun Oct 30 02:01:26 UTC 2011

At 7:22 PM -0400 10/29/11, Raymond Wagner wrote:
>On 10/29/2011 14:36, Mark Lord wrote:
>> On 11-10-29 01:13 PM, Craig Treleaven wrote:
>> ..
>>> Is the simple rule of thumb that each commflag job should have its
>>> own core?
>> That would depend upon how fast the cores are.
>> On my 2,6GHz Core2 duo backend, commflag takes only 10-25% CPU on a single core,
>> so there's no problem with multiple commflags at once per core.
>Real time comflagging may only use that little bit of power, because it
>is governed to the recording rate.  It actually uses much less power
>than playback, due to a special facility in FFmpeg that allows MPEG2 to
>be decoded at a much lower resolution (that capability, and subsequent
>speed boost, may end up lost in future syncs).  Post recording
>commflagging will eat up as much CPU as it can, and with decoding and
>processing in separate threads, I've seen it take most of two cores.
>It all comes down to the issue that the jobqueue is not designed to
>handle scaling with multiple types of work loads.  Allowing several
>simultaneous jobs may work for real time commflagging, but would be a
>very poor choice for normal commflagging, high IO tasks like lossless
>transcoding, or CPU intensive tasks like normal transcoding.  Similarly,
>one simultaneous job works well for those loads, but leaves your system
>largely idle and wasted for real time commflagging.  It's a difficult
>problem to solve, and there are a couple tickets on trac documenting
>attempts that introduced more bugs on their own.

Thanks, Raymond.  By necessity, most of my commflagging has been post recording--it makes sense that real time would be waiting for the recording to be received.

Does it seem reasonable that, say, a dual core, 3.2Ghz AMD Athlon II could keep up commflagging 4 simultaneous recordings?


I'll spend the money on a more-capable CPU if it is needed but, obviously, I'd prefer not to if it isn't needed.  And save the electricity and heat.


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