[mythtv-users] CPU load when watching TV

lee lee at yun.yagibdah.de
Tue Dec 15 11:58:41 UTC 2009

On Mon, Dec 14, 2009 at 11:01:48AM -0500, Rod Smith wrote:
> On Monday 14 December 2009 08:22:52 am lee wrote:
> > room. When I want to watch something on TV, I create a DVD for that.
> To me, this sounds very awkward. Some people build dedicated front-end systems 
> for this purpose. Such systems don't even need a disk; they can be booted 
> over the network. Another approach is to use a video distribution system to 
> move the video from the computer in one room to the TV in another room. A 
> friend of mine has a setup like that; his Myth box is in his basement and he 
> watches it upstairs.

Yeah, it is awkward --- but the only way I have for now. And what
other devices are there than computers that could be used as frontends
for mythtv?

Perhaps I can put a Mac into the living room, we'll see ... I'll try
to put a frontend on it, anyway.

> > 23189 lee       40   0  566m  57m  23m S   17  1.5  30:36.82 kwin
> >  7271 lee       40   0  787m 137m  42m S   14  3.5   3:04.45 mythfrontend
> > 23044 root      40   0 3210m  51m  10m S    5  1.3  19:02.28 Xorg
> >  5585 mythtv    40   0  582m  27m 9884 S    1  0.7   2:35.99 mythbackend
> If this is typical, and nothing was spiking or at an unusually low value for 
> playback, then I'd say that MythTV is consuming very little CPU
> time.

It shouldn't use much ... I'm using the cpufreq stuff, and the
ondemand governor sets the cores to 800MHz mott. I don't know what
effect that might have on the CPU percentage shown. In theory, 25% at
800MHz should be like 6% at 3400MHz ...

> On a dedicated Myth box, the 17% CPU time consumed by kwin would be
> unacceptable.

Why would it be unacceptable?

> I'm actually surprised that kwin is consuming so much CPU time. Does 
> its CPU consumption go down when you stop playing back video? It could be 
> there's some inefficient coding in there that's causing its CPU needs to 
> skyrocket with a dynamic display. For comparison, I'm using XFce and its 
> xfwm4 window manager on my desktop system, and its CPU use doesn't even make 
> the list that's displayed by top in a standard window. Ditto for openbox on 
> my dedicated MythTV box.

Hm, you're right, it does use a lot CPU. It goes down maybe 1% or 2%
when I pause the playback. I wonder what it's doing ...

> That said, your overall CPU use is low enough that I wouldn't recommend 
> switching away from KDE, or changing its window manager, just for this. If it 
> caused stuttering or other CPU contention issues, it might be worth 
> switching, and likewise if this were a dedicated MythTV system. Since you use 
> the computer as a desktop system, though, changing your window manager will 
> require you to change the way you use the system, at least a little, and 
> that's not worth it.

Well, I'm using kde only since a few days. I've been using
enlightenment for years, then tried fvwm2 for a while. It's nice to
try out new stuff every now and then ...

> > > Why do you say that suspend-to-disk is dangerous? If you've got specific
> > > references saying it's unreliable, I'd be interested in seeing them. If
> > > not, I wouldn't worry about it.
> >
> > Just look at all the warnings in the help of the kernel
> > configuration.
> I don't read the warnings as being that dire. The fsck utility does
> a good job of recovering from such damage, and has done so on my
> laptop a couple of times. Of course, if you think you're likely to
> frequently forget you were in a suspended state and change hardware,
> then playing it safe makes sense. For me, this wouldn't be an issue
> on a dedicated MythTV box, but it could be on other systems.

It takes only one time where it goes wrong, and all my data would be
lost. Chances are that it will go wrong at some time.

> > > The biggest load is when mythfilldatabase runs
> >
> > So far, I haven't noticed any of that. I'm only getting EPG data as
> > there doesn't seem to be any other useable source available.
> I'm in the US and so use Schedules Direct and mythfilldatabase. I'm less 
> familiar with how Myth handles EPG data.

It just reads it? ;) I think the backend keeps going through the
channels to read the info all the time, or regularly. These updates
don't seem to generate much load.

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