[mythtv-users] Low Power Frontends (in anticipation of nvidia's new API)

[jedi]

On Thu, Dec 18, 2008 at 08:39:13PM +0100, Jan Ceuleers wrote:
> David Brodbeck wrote:
> > Jan Ceuleers wrote:
> >> Do you know whether running mythfilldatabase with a high nice value 
> >> alleviates at least that side of the problem? In other words: if the 
> >> application that invokes the database has low priority, do the database 
> >> threads somehow also get executed with low priority?
> > 
> > No.  They run with the priority of the mysql process.
> 
> That's what I thought: threads don't get created on demand. But I was 
> wondering whether the database API somehow includes a priority 
> parameter, or indeed whether the database has a priority policy 
> framework. I guess not.
> 
> > ...you need to figure out where the actual problem is before you try to
> > solve it.  Is it that mysql is consuming a lot of CPU?  Is it that
> > mythfilldatabase is consuming a lot of CPU?  Or is it because all of the
> > database writes saturate the I/O bandwidth?
> 
> In my case it's mythfilldatabase that consumes a lot of CPU, so I run it 
> at nice -19. The amount of CPU used by mythfilldatabase is about twice 
> the amount consumed by mysql.
> 
> But the problem I'm trying to solve is not the execution speed of 
> mythfilldatabase, but rather that a mythfilldatabase run has minimal 
> impact on any foreground processes. My current solution is to simply run 
> mythfilldatabase in the middle of the night but I'd like to understand 
> what my options are for when I do have to run it during showtime.

    That's the usual answer to a problem like this...

    For similar reasons, I don't run jobs during "primetime". MythTV can
suck the life right out of my network when it's running full bore on my 
master and all of the remote machines doing transcodes and commflags. 
It's all that the master can do to just keep up with demand for NFS.
Load averages shoot up and response times degrade intolerably on any
frontend that's being used as such.

    A computer is like a cabal of elves...