[mythtv-users] Mythtv stuttering - help debugging

mythtv at corwyn.net mythtv at corwyn.net
Wed Mar 18 22:24:05 UTC 2009



Environment:
I'm currently running mythtv-0.21-198.el5 on CentOS kernel 
2.6.18-92.1.18.el5 with a Happtpauge pvr-350

I have a server that is frontend and backend, but I normally watch 
myth using mvpmc on the Haupptpauge MediaMVP.  The problem I see is 
that after running for a while the video starts stuttering. the 
buffer indicator on the mvpmc shows that the buffer isn't staying full.

the mvpmc code has a memory leak that can cause stuttering, but a 
soft and hard reboot of the mediamvp only rarely resolves the 
problem. A reboot of the server on the other hand tends to resolve 
the problem for a few hours.

I've swapped out the network cable and switch that connects the two 
devices. (although the NIC isn't reporting any errors) I've pondered 
IRQ issues, nic driver issues, drive performance issues, heat issues 
on the mvpmc. The system isn't running another recording, or 
performing and tasks like transcoding/commercial flagging. However, I 
think the problem is directly related to myth somehow.

If I'm in a stuttering state, I can exit the myth part of the mvpmc, 
and view a mpg through the mvpmc with no problem, and a higher rate 
(6 mpbs, where Myth tv is typically 4 mbps according to the mvpmc). 
Exiting that video and going back to myth, and I'm immediately back 
to stuttering.

So I think it's related somehow to myth (reboot of the server fixing 
it, watching plain video sans myth through the mvpmc code works 
fine).  However, stopping and starting the mythbackend service and/or 
the mysqld service also doesn't "reset" the problem

the only log event sin mythbackend.log are
2009-03-18 18:03:44.235 MainServer::HandleVersion - Client speaks 
protocol version 8 but we speak 40!
2009-03-18 18:03:44.240 MainServer::HandleAnnounce Playback
2009-03-18 18:03:44.241 adding: 192.168.2.57 as a client (events: 0)
2009-03-18 18:03:44.243 MainServer::HandleAnnounce FileTransfer
2009-03-18 18:03:44.244 adding: 192.168.2.57 as a remote file transfer

Disk performance looks ok:
[root at glutton log]# hdparm -tT /dev/sdb

/dev/sdb:
  Timing cached reads:   3860 MB in  2.00 seconds = 1929.88 MB/sec
  Timing buffered disk reads:  230 MB in  3.02 seconds =  76.06 MB/sec
[root at glutton log]# hdparm -tT /dev/sda

/dev/sda:
  Timing cached reads:   3756 MB in  2.00 seconds = 1877.72 MB/sec
  Timing buffered disk reads:  228 MB in  3.01 seconds =  75.74 MB/sec

top results are equally not informative:
top - 18:25:33 up 18:03,  1 user,  load average: 0.10, 0.12, 0.09
Tasks: 115 total,   1 running, 114 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.3%us,  1.5%sy,  0.0%ni, 98.2%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   1800232k total,  1545056k used,   255176k free,    43216k buffers
Swap:  2024180k total,      124k used,  2024056k free,  1051948k cached

and ethtool reports 100 MB/FD (it was GB/FD until I swapped out the 
switch, no difference)

the my.cnf settings match what's suggested in the MYTHTV HOWTO for 
optimizing performance http://www.mythtv.org/wiki/Optimizing_Performance

Any pointers on where else I can look to debug the problem?

Thx.

Rick




Rick Steeves
http://www.sinister.net

"The journey is the destination"



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