[mythtv-users] What to do with lots of RAM?

Stephen Worthington stephen_agent at jsw.gen.nz
Mon Aug 17 09:15:38 UTC 2015


On Sun, 16 Aug 2015 20:46:01 +0100, you wrote:

>Jerome Yuzyk <jerome at supernet.ab.ca> wrote:
>
>> My "new" 0.27.4 FE/BE has 4G of RAM, only 1M of which seems to be used, leaving me to wonder what I can do with the rest of it to speed up MythTV as much as possible. Other than running rsyncd to be a backup for my other machines, the box is only going to run MythTV and maybe a browser for Internet content. 
>> 
>> 
>> MySQL tuning is an obvious candidate, and I've already added some MySQL settings from
>> https://www.mythtv.org/wiki/Installing_MythTV_on_Fedora#MariaDB_performance
>> 
>> 	key_buffer = 16M
>> 	table_cache = 128
>> 	sort_buffer_size = 2M
>> 	myisam_sort_buffer_size = 8M
>> 	query_cache_size = 16M
>
>Ignore other people's numbers - use mysqltuner.pl.
>Note that you'll need to adjust your settings over time as the tables (particularly oldrecorded) get bigger. Read up on what each setting it suggests actually does, and be prepared to take a while as you need to leave the system to run for a while to get valid stats after making changes.
>
>Your aim is to try and get all the tables to stay in ram all the time - that minimises disk access.
>
>Other than this, just let the system use the extra ram for caching. For one thing, it'll help with things like commflagging and trancoding new recordings by allowing more of the new recording to stay in ram.

With sufficient RAM and a modern processor, you should be able to run
commercial flagging in real-time, with at least one recording being
flagged on each processor core.  Doing that means that the flagging is
done from the buffers/cache instead of having to read the data back
from disk again, greatly reducing the disk usage and allowing more
recordings per drive to be done at the same time.


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