[mythtv-users] Backend settings for max simultaneous jobs and cpu usage

[Michael T. Dean]

On 12/28/2011 12:28 PM, steve wrote:
> Greetings and happy holidays.  I am looking for advice on how to choose
> settings for Max simultaneous jobs and CPU usage on the backend setup.
> I have a Core 2 Duo E8400 3ghz processor, and want to make best use of
> it.  But I have looked around the wiki and done some searches on this,
> and am not turning up much.  What are the principles for selecting
> settings for two these options?

My own personal opinion is that all users should use Medium for "CPU 
Usage" (= run full speed with nice 17) with the exception of people who 
have severely underpowered systems, who should use Low (= run with nice 
17, and sleep after every few frames are processed to preemptively give 
other tasks priority).  How do you know if you have a severely 
underpowered system?  If you see glitches/issues when recording and 
running a single job on Medium, you have a severely underpowered 
system.  Note that High CPU Usage is run full speed without any nice 
setting and can get in the way of recording even on extremely-powerful 
systems.

And, I recommend a max of 1 job enabled at a time for anyone with a 
single- or dual-core CPU.  This, however, is a conservative setting, and 
you should be fine with one job per core, assuming you use Medium or Low 
CPU Usage.  If you use High CPU usage, you should definitely use #cores 
- 1 (or even -2) jobs (and they'll probably complete even faster with 
Medium + #cores than High + #cores - 1).  Enabling more than one job per 
core/CPU probably won't speed things up and may even slow things down.  
I'll let you all make up your own minds whether to count 
SMT/HyperThreading as a core for these purposes.

Note, however, that 1 job + Medium CPU works extremely well for anyone 
who watches tonight's recordings tomorrow or after.

IIRC, Raymond Wagner has a patch in progress that replaces the job queue 
with a much smarter one that takes into account things like recording 
priority, etc., when assigning jobs.

Mike