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

[sonofzev at iinet.net.au]

On Wed Jan 20 22:20 , Jerry Rubinow  sent:

>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 frontendAthlon 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



Not sure about your particular scenario.. But logging increases disk-write
activity ... Working in call-delivery systems (call centre applications) we
generally recommend to our customers they have logging kept to a minimum unless
we are looking for the cause of a fault... 

If you have logging turned on, it's best that it isn't on the same disk as your
Myth Database..