[mythtv-users] Realtime - Kernel Scheduler - Preemption

Steve Skarda steveskarda at gmail.com
Fri Apr 7 13:50:43 UTC 2006


I have been trying to fix problems with a 100-200mS delay in audio and that
has created a lot of questions around how the Linux Schedule works and
whether or not MythTV is getting the CPU it needs or not.  Here are
questions that I am hoping someone can help shed light on.

1).   I have realtime enabled in Ubuntu.   When I launch a recording, "using
realtime prioirty" shows up in the log.   When I look at TOP, under the PR
column, I see that Mythfrontend priority is similar to other programs,
around the 30's.  However, there are a few tasks, with 'RT" as priority,
presumably reatltime.   Should I expect to see RT for mythfrontend task as
well?

2).  Any idea how to up the task priority on mythfrontend for the Linux
scheduler?

2).  I tried compiling a new kernel with preemptive scheduling turned on (my
old kernel was set to voluntary/desktop).   I also tried to update PAM to a
newer version.  I am not sure what went wrong but Mythfrontend CPU went near
100%.  This is very unusual for my 3.2Ghz Pentium.   Older posts seem to
suggest that the problem is that mythfrontend can't get the CPU as often as
it needs.  I tried rtlimits, pam, realtime-lsm.  Nothing seemed to help.  I
always see "using realtime" in the logs but CPU is high causing prebuffering
pauses.  Not sure if the problem is with my new kernel or something I messed
up in the PAM.

3).  I have gotten no where near solving my audio sync issues.  I have been
considering compiling a kernel with Ingo's realtime patch.  There have been
two posts on that subject.  One saying that MythTv works and another asking
if it is possible.   Does anyone have further information on this?  So far,
I have had trouble getting it to compile and I am expecting to have
difficulty getting NVidia to work.

My system for anyone that is curious:
Ubuntu Breezy
Vanilla 2.6.15 kernel
Pentium 4 3.2Ghz w/HT
Nothing unusual in the logs
MythTv from SVN

Steve
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mythtv.org/pipermail/mythtv-users/attachments/20060407/1a855f60/attachment.htm 


More information about the mythtv-users mailing list