[mythtv-users] Will moving to DDR-400 memory from DDR-333 improve performance?

[Joe Votour]

> On Sun, 2006-22-10 at 23:37 -0700, Yeechang Lee wrote:
>> I currently have 1.5GB of DDR-333 memory
>
> Does it not strike anyone else that this kind of memory requirement for
> a STB is absolutely ridiculous?
>
> OK, 1.5GB is probably overkill, but the 256MB I have in my FE/BE has, as
> of 0.20, become far too small to be able to run a full myth system in.
> Even with a 1G of swap, during a mythfilldatabase the machine thrashes
> the swap and frequently the OOM killer is invoked and ends up killing
> mysqld.
>
> Why is Myth using so much memory as of 0.20?
>
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>  6846 root       0   0  165m  39m  11m S  0.0 15.9 365:30.06 mythfrontend
>  8153 root       0   0  206m  15m   9m S  0.0  6.4  11:44.56 mythbackend
>
> Like seriously... 206MB for the backend and 165M for the frontend?
>
> Is this just my system or are most peoples 0.20 systems showing the same
> kind of memory use?
>

It is unfortunately the bloat of Linux and X11/Qt sneaking up on us. 
Believe me when I say that unfortunately, I could not do a better job
(except maybe use something other than Qt, but that's just because I'm a
poor C++ programmer).

If you want to trim down the memory, then you basically need to make the
machine a dedicated MythTV machine, with a stripped down kernel for only
your hardware and maybe even compile MythTV against uClibc.  You'd also
want to selectively compile options out of MythTV as well.

Most Linux-based set-top boxes use a CPU in the range of 200MHz and 32 or
64MB of memory.  Of course, they also don't use X (they use MicroWindows
or something smaller than X), they have dedicated MPEG-2/MPEG-4 decoding
chips (thus no need for software codecs), and their kernel is stripped
down to less than 1MB, they use BusyBox, etc., etc.

Also, most people are running both the frontend and the backend on the
same machine (although I am not).  This has higher memory requirements
than just a regular set-top box.  In terms of the servers that the cable
operators use, they are massive, and the set-top boxes, as I described
above, are puny - unless they run that bloated OCAP or OpenTV crap.

All in all, the memory usage isn't too bad for a Linux machine doing this
stuff.

-- Joe


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