[mythtv-users] Mythbackend causing high load

[Mike Benoit]

My best "guess" is it has more to do with IVTV then Myth, but thats just
a pure guess based on the fact that I was getting all kinds of buffer
overflows from IVTV, until I upgraded to v0.4.5 when they stopped (at
least being logged).

It seems to be pretty much random for me now, some shows record
flawlessly, others are so bad that Myth thinks a one hour show is only
23mins, I assume because it has lost that many frames. The show is of
course unwatchable. 

I'm running "dstat -v 10" and logging the output so hopefully that will
give me a hint as to whether it really is an IOBOUND issue, or something
else. Last time I managed to catch Myth sucking up all the CPU during a
recording it was all in SYS CPU time, not USER which you would expect it
to be. This also leads me to believe that it is not actually Myth
causing the issue, but either IVTV or some filesystem issue.


On Sat, 2006-06-17 at 00:06 -0400, Jeff wrote:
> I was curious today so I took a look at one of my bad recordings (they
> were all bad from the last few days) and sure enough going through the
> recording frame by frame, there is an obvious break in the motion
> where frames have been dropped. This is not a playback issue, it is a
> recording issue.
> 
> Unfortunatly it isn't related to transcoding either. I've disabled all
> transcode jobs and the log file shows no evidence of any transcoding
> being started. However all of my recordings from today show the
> "stutter" problem. Interestingly though I didn't have any of the
> IOBOUND errors logged.
> 
> At the moment the system is recording a show and mythbackend is
> running at 76-90% CPU (Athlon 1400). I've tried a few different things
> to try and figure out what its doing but no luck. oprofile shows a
> picture like this so I may have to build a kernel to do this or maybe
> just build mythbackend and try gprof instead.
> 
> CPU: CPU with timer interrupt, speed 0 MHz (estimated)
> Profiling through timer interrupt
>           TIMER:0|
>   samples|      %|
> ------------------
>     23504 98.6610 no-vmlinux
>       138  0.5793 libc-2.3.6.so
>        22  0.0923 mysqld
> <snip>
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-- 
Mike Benoit <ipso at snappymail.ca>
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