[mythtv-users] mythbackend

[Ray Olszewski]

At 04:09 PM 5/22/2003 -0500, Hellboy wrote:
>I noticed when I was running MythTV, and watching Live TV that my CPU
>utilization was through the roof. My Athlon 900 was running between 88% and
>94.8% and leaving me with about 8MB of RAM left out of 384MB. Needless to
>say, that the box crashes for what I'm assuming is too heavy of a workload.

This description contains several (probable) misunderstandings.

1. You do understand, I hope, that "live TV" is not really "live". It is 
buffered, so the system has to run both an encoding process (mythbackend 
does that) and a decoding process (mythfrontent does that). So high CPU use 
is normal in this setting, especially for a relatively low-power system 
like yours.

2. The Linux kernel handles memory use in wuch a way that after a system 
has run for awhile, it will always report near-100% RAM use (I mean here 
the simple report that "top" provide, not the better one that "free" 
provides).

3. Even under heavy loads like this, systems do not normally "Crash", so 
there is no "needless to say" about it. See below for more on this one.

>I used SSH to log in remotely, and noticed that there were between 4 and 6
>processes for mythbackend that were running. Also, there were 2 or 3
>instances of mythfrontend running as well, each taking up 33MB of RAM. The
>number would fluctuate (one minute there would be two processes, the next
>would be six, then back again).

Both mythfrontend and mythbackend are threaded apps, and threads show up as 
multiple "processes" in top and ps. While what you are *seeing* could be 
indicative of a problem, what you are *describing* is way too vague to 
distinguish what you are seeing from normal operation.

>According to the docs, an 800MHZ P3 should be able to encode and decode
>allowing for Live TV  watching (although I'm assuming not much else).

Do the docs really say this? Without qualification? Your use of RTJPEG 
halps lighten the load, but even so, I'd be surprised if this system, or 
yours, can handle the load at the standard (480x480) capture size. My Cel 
1.7 GHz, running MPEG4, can just barely do it.

>I
>realize my CPU specs are not much higher than the bare minimum, and my RAM
>is lower than the 512MB but it looks like it should be able to pull it off.
>I'm using RTJPEG at the default cap res also.
>What concerns me is the multiple instances of both programs running, and I'm
>wondering if this normal, or if it is something I could pare back on. Sorry
>if this is kind of a noob question, but, well, I'm kind of a noob at this.
>Thanks for the help.

Aside from the crashes, are you seeing any of the usual problems that 
people describe in messages here when a MythTV system cannot keep up with 
the load?

If the crashes are the only problem, I'd look elsewhere than Myth itself 
for starters ... a bad component (mobo, CPU, RAM), a miscompiled kernel 
(trying to run DMA on a drive without including kernel support for the 
mobo's IDE chipset), overheating. It's hard to be specific without a better 
description of the symptom than "crashes" ... does the system freeze up and 
require a power-cycle reboot? Is there a kernel oops? Or what? After the 
system has "crashed", does it respond to pings? What else can you tell us 
about the crashes?