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

[Jerome Yuzyk]

On Monday, August 17, 2015 09:15:38 PM Stephen Worthington wrote:
> 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
>
> >On Sunday, August 16, 2015 08:46:01 PM Simon Hobson wrote:
> >
> >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.

Thanks Simon. I got and have run mysqltuner.pl and applied its recommendations and made it a Monday-am cron job. Since I migrated, my database has 9 years of history in it for making good recommendations.
 
> 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.

I was wondering if I could use this feature. It seems all-or-nothing though, not per-recording, so I put aside trying it out. But, with hardware encoding and VDPAU decoding my CPU only gets busy during commflagging, and even then not much. I am currently commflagging High Quality SD recordings at 20 minutes per hour (95fps).

I have a re-purposed Core2 Duo E4500 2.2G with 4G and reading a couple old list threads it seems I have enough horsepower for my simple SD recording environment. I'll try it. Thanks for prompting me to look at it.


-- 
A little of Jerome's MythTV World: http://mythtv.bss.ab.ca