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

[Paul Catchpole]

Indeed, you've raised some good points. Haven't got enough spare brain-power
during the working day to evaluate. Will give it some more thought later. 

What do you have your swappiness factor set to? 

I've reduced mine significantly, to 0.15 on the Frontend and 0.3 on the
backend from .6 default. This, I believe (:-)) should ensure the systems use
ram from the page/disk caches to service processes rather than from swap. I
especially don't want my frontend to swap over NFS more than necessary. 

Didn't mean to spread disinformation...

Paul 

---
Paul Catchpole CCNA
Consultant Network Specialist
 

-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Brian J. Murrell
Sent: 23 October 2006 16:48
To: Discussion about mythtv
Subject: Re: [mythtv-users] Will moving to DDR-400memory from DDR-333
improve performance?

On Mon, 2006-23-10 at 16:37 +0100, Paul Catchpole wrote:
> For what it's worth...
> 
> The RES column is (according to the docs for 'Top') the most appropriate
> descriptor for actual memory usage: 

Of course it is -- if you are just trying to judge physical ram usage.
But physical ram usage is not the issue here, it's VM usage.  Think
about how much disk thrashing is going to be needed to get what is not
in physical memory back into physical memory (and what is in physical
memory out to disk so that the incoming has somewhere to go) when it's
needed.

> 16735  8.4  600m 568m  31m  944 562m 7344 1631    0 S  15   0  0.7
> mythbackend

LOL.  So when some of that 568M of swapped out data is needed for
something it's going to thrash your disk swapping it back in from swap.

> 10158  3.2  145m 133m  12m 5712 135m 2284 2695    0 S  16   0  0.0 mysqld
> 
> So on the backend (2x DVB-T, 384mb RAM, P4 2.4ghz), mythbackend is using
> 31mbytes of RAM and mysql is using another 12mbyte. 

Yeah, at the moment.  What do you think your disk is going to do when
one of those process actually wakes up to do something and needs some of
that non-RES data?

> Just for interests' sake... 

Indeed.  Seems your numbers are far worse than mine even.  A 600MB
backend process!  Aye Karumba!

b.

-- 
My other computer is your Microsoft Windows server.

Brian J. Murrell