[Gllug] FreeNX vs VNC?

[damion.yates at gmail.com]

On Tue, 27 Oct 2009, KJS wrote:

> I have a number of users logging in over VNC and leaving hanging
> desktop sessions which is using up loads of memory (some users are
> running a couple of VNC sessions...).

The advantage of connecting in to existing sessions is pretty great,
like screen(1) but with a GUI.  If users aren't aware of this and are
creating new ones each time, you need to educate them.  Are you sure
these sessions are left hanging by mistake?
 
> Which is running X & Gnome etc for each user and causing the server to
> swap out !

You need a more powerful machine, what if they all chose to log in and
work at the same time anyway?  Hanging sessions detached whilst a user
has created a new one is obviously wrong, this is your implementation of
the attaching method gone wrong IMO.  But you need more ram if you want
this as a viable solution.  Sorry just noticed the last thing you wrote,
if this isn't something you're promoting this machine is used for and
it's users own scripts re(or new)connecting to sessions, then yeah, I'd
ban VNC ;)
 
> I am wondering if I switch to FreeNX would this over come the problem?
> I remember reading that FreeNX shared memory with other process that
> used the same application (like MS TS does).

It's exactly the same other than being a bit fancier in some respects to
how it draws stuff and communicates the display in its protocol.  It
should seem a lot more responsive.
 
> I wondered if this was the case? As I can't find any info to back it
> up on their website.

The binaries, libraries etc will all be read from disk and cached in any
spare ram.  Other people loading the same stuff will be reading from the
same cache.  Only parts that need to be executed should be loaded,
you'll gain some shared memory usage inherently due to the goodness of
modern OS design (I can't argue this is Linux specific, or even UNIX
specific as the other OSes now also do this).

Only working data parts of the running processes where changes are
made, be where the OS copies that memory to a new part of RAM and take up
space per user.  You can check in top or ps what the resident vs actual
vs whatever other types of memory usage each of these uses.

It should technically be worse if some users use KDE and others Gnome as
you end up with both in use.  On the other hand I have a feeling that
the storage needs for gnome processes might not lend themselves well to
being shared for many users.

Damion
-- 
Gllug mailing list  -  Gllug at gllug.org.uk
http://lists.gllug.org.uk/mailman/listinfo/gllug