[mythtv-users] How could logging cause myth performance issues?

Jerry Rubinow jerrymr at gmail.com
Thu Jan 21 03:20:42 UTC 2010


Since switching to 0.22, I'd been having frame drops in the recorded files
(problem was definitely in the recording, not the playback), delays in
frontend activity.  The frame drops coincided with frontend activity while
recording (playing back files, deleting files).  Network showed no errors.
 CPU usage on backend remained low (much less than 50%) throughout.
 Upgrading from weekly 0.22-fixes to trunk had no effect on the issue.

Long story short, turning off all logging except for "important" messages
caused all issues to go away.  The logging options had been the mythbuntu
default (important,general,record,channel).  Turning on more logging options
made the issues worse.  Size of log file varied per day between 15MB and
30MB.  This doesn't seem like enough throughput for disk i/o to cause
network packets to fall off the queue.  The disk has dma enabled, and the
recording storage is on a different drive than the system drive.

Does anyone have any ideas what I might look into to figure out why logging
triggered these problems?

Myth setup:
Revo frontend
Athlon 64 3500 backend, with HDHomeRun and HD-PVR tuners
Mythbuntu 0.22 fixes weekly builds (reverted after trunk didn't help) with
Ubuntu 9.10

Before upgrading to 0.22, I was running 0.21-fixes on an older computer
(Asus A7N8X-X) no issues.  I upgrade to 0.22-fixes and added the HD-PVR, and
started having problems.  Switched the BE onto the Athlon 64 box, problems
didn't change.  Problems occurred whether or not I was using the HD-PVR.  I
believe (but I can't swear) I had the same logging options turned on when I
was running 0.21.

Thanks for any ideas.

-Jerry
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