[mythtv-users] Frontend hogs the CPU

Jim Carter jimc at math.ucla.edu
Sat Jul 14 05:37:09 UTC 2007

I've installed MythTV for the first time and am having major pains. 

Upon non-obvious events, either during watching live TV or when
the menu is shown, the frontend will get into a high CPU state in which,
according to strace, it does
    select((17, [14 16], NULL, NULL, {0, 10000}) = 0 (Timeout)
over and over; I never saw the FD's being ready, always it timed out.  
(Come to think...  timed out selects would make the process always be in
run state but would have expended relatively little CPU, so likely 
another of the three reported threads was hogging the CPU.)

The result of the latter behavior was that the user interface was 
extremely sluggish: a full minute for an arrow key to have a visible
effect, for example.  But it wasn't actually frozen.  

This was with the G.A.N.T. theme.  After I switched to Blue, which may
or may not have been relevant, and after two hours of live TV
(surprisingly, with few or no dropped frames despite 100% CPU usage and
a load average of 4.9), I returned to the menu and spotted a behavior:
CPU use is 0, press arrow key once, CPU goes to 100%, wait, effect is
seen on screen, CPU drops to 0.

The UI is configured to use OpenGL.  Normal GL apps such as glxgears and
MESA demos run normally.  The MythTV UI seemed faster when OpenGL was
turned on, than when it was off.

Does anyone have any idea what's going on, and what to do to make it
stop hogging the CPU?

My configuration:
    Dell Dimension 4100 -- Intel Pentium III "Coppermine" 1.0 GHz
    256 Mb RAM.  40 Gb disc.  
    Operating system: OpenSuSE 10.2, kernel
    Graphics: nVidia GeForce2 MX 400
    MythTV version: 0.20
    Capture card: pcHDTV HD-5500
    Leading drivers: cx88_blackbird cx2341x cx88_dvb etc.

Yes, I know the system is a bit underpowered.  MythTV is currently in
a competition with Windows Vista Media Center Edition, which we loathe,
and if $spouse judges that MythTV isn't as awful as MCE then it will
get to run on an almost-new Dell Dimension E510 dual-core at 1.8 GHz
with a Seagate 160 Gb disc.  But MythTV has to actually perform first.

James F. Carter          Voice 310 825 2897    FAX 310 206 6673
UCLA-Mathnet;  6115 MSA; 405 Hilgard Ave.; Los Angeles, CA, USA 90095-1555
Email: jimc at math.ucla.edu  http://www.math.ucla.edu/~jimc (q.v. for PGP key)

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