[mythtv-users] LiveTV pauses when transcode job completes / IOBOUND errors

Matt Doran matt.doran at papercut.biz
Tue Mar 6 12:26:06 UTC 2007

Hi there,

I've recently setup a mythtv box, and am very happy with the result.  
However, I often see a 1 or 2 second pause watching live TV, and I've 
figured out that this always seems to correspond to the completion of a 
transcode job.  I'm running Ubuntu Edgy, with Linux kernel 2.6.20, and 
mythtv 0.20-fixes (svn r12509).

It is a combined frontend/backend and is a pretty powerful machine:

    * AMD X2 3600+ (dual core)
    * 1GB ram
    * Asus M2NPV-VM motherboard (with onboard Nvidia 6150)
    * 3 DVB-T tuners
    * WD SATA2 HD

It has no problem handling commflagging and transcoding while watching 
TV, but when the transcode completes it has troubles.  I only allow one 
job to run at a time, and there is no other load on the box.  To me it 
seems that the IO of deleting the original recording is probably causing 
the problem.

Here's the backend logs showing the problem:

    2007-03-06 22:47:25.430 Transcoding
    /var/lib/mythtv//2503_20070306203500.mpg done
    2007-03-06 22:47:28.630 TFW, Error: Write() -- IOBOUND begin
    cnt(9400) free(4899)
    2007-03-06 22:47:32.930 TFW, Error: Write() -- IOBOUND end
    2007-03-06 22:47:33.061 JobQueue: Transcode Finished: CSI: Crime
    Scene Investigation "Who Shot Sherlock?": 1.1 GB (High Quality)

I have the "Delete files slowly" option enabled, because when I was 
going through setup because it sounded like a good idea.  Maybe this 
makes things worse?  I'll try disabling the slow delete to see if it 
improves the behaviour.

Any ideas on how to improve the behaviour?  What could be causing this?  
Any experience with the "delete files slowly" option?

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