[FreeNX-kNX] NX screen refresh performance

Tue May 18 11:56:33 UTC 2010

Toni Asensi Esteve <asmond at orange.es> wrote on 18/05/2010 08:43:50:

> Les Mikesell wrote:
> 
> > It might help a bit to keep your screens as 'plain' as possible,
> > removing images and background gradients where you can to make it more
> > likely to be able to compress large blocks and cache and reuse them.
> 
> OK!. I created a new page about it:
> 
> http://openfacts2.berlios.de/wikien/index.php/BerliosProject:FreeNX_-
> _FAQ/Screen_Performance
> 

Hi Toni

Oh, so there is a FAQ !!

I thought you were joking !!

It might be worth adding a couple more things if you are maintaining a
FAQ.

For example, you can customize for quality at the expense of speed (or
visa versa) as far as the link is concerned
 or 
compress for slow links verses speed as far as loading the CUP/memory is
concerned 

You can disable caching etc on an old/under-rescourced workstation if
the link is quite quick which can save you having to buy hardware.

And

There are the usual issues regarding multi user machines which are often
more significant to the performance of an NX machine then NX its-self.

eg.

Image quality

If you want screen quality then upping the "custom jpeg quality", or
going to RGB only is a good idea but quality will of course hit the link.

Don't forget the Server<->Internet link, not just user's WAN links.

Low quality will help the link, but there will be a hit on the CPU if
you do high compression.

Response Time

If you disable the shared memory extension in the client, then
nomachine say you may get a quicker response time reaction 
to screen changes, ( I haven't bother trying it myself, but if you
use a fast LAN then it might be a good default )
and
disabling deferred screen updates on a fast WAN link may give
a less jerky response. It is a default LAN setting.

Link Speed

A slow link can run better with jpeg set to very low quality, but I 
wouldn't advise that for ordinary users because you can barely 
see what you are doing.

I've seen even "power users" who, for example have been told
about this sort of setting to give them the option of using it in a
cafe, fail to re-set it and then complain about link quality.

Link latency and packet loss can cause time out issues which no
amount of tweaking will fix.  A "slow" link may just be a cafe
with too many users reading email for a session based application.

Don't set up remote printing, shared drives unless you need them.

Server load

Disabling compression and encryption will reduce server load.

If your WANers use a VPN client you only need to encrypt if you
don't trust your LAN ( don't laugh, I've seen wi-fi used to monitor
(larger) VLAN packets being broadcast over London, Windoze
passwords, the lot )

and . . .

Useful work only

Running an application rootlessly, misses out the rest of the 
desktop, which can stop users running games, screensavers,
email, web browsers, apps they aren't using etc

Cost effective

In my view, tweaking is all well and good, but for a "reliable high
quality user experience" it's cheaper and more effective to  keep
reasonable defaults and :-

1/ stop the users using things they don't need to do
2/ add £200 worth of memory
2a/ get another CPU core ( Yup, can still be cheaper)
3/ don't use slow links ( there's always another cafe. take up thy
         st*rbucks card and walk )

. . . . rather than set up test-beds to compare RGB to high Q jpeg
over a variety of departmental tasks.

If you like that sort of thing, and the alternative is testing the
backups well and good.

Personally I find testing backups more rewarding.

My tuppen'orth

The most significant issue with performance is:-

don't let the users know that there are setting which can be
changed, else you'll get just-in-case/live-in-hope complaints
on the off chance that you can speed things up.

The more users fiddle, the more "witchcraft" type of associations
they make between cause and effect and the more thay fiddle.
It's not just restricted to 17th century Lancashire or Salem.

You can only tweak for one senario !!

Ye bottom line

Don't let your hardware let you down - you can only get so much
out of it.
Tweak your user-base (& management) not your setting.
Use tweak-time to do something more productive.

> So that new questions about this subject... can be redirected to that 
page. I
> also added those instructions that we use in our company; feel free 
> to correct 
> me: 
> 
>       - If, for example, you have a slow connection, you use the NX 
client and
>       you are using programs in the server that have a normal 
presentation 
>       ( those which show text, numbers, lines, squares, and so on in the
>       screen... but not photographs or gradients) it's better to 
configure the
>       client to use RGB compression in the menu "Display > Settings".

RGB is lossless encoding, ie mostly don't compress

Personally, I find it slower than a steamroller, unless on a LAN link.
jpeg is everywhere for a reason !!

> 
> Greetings:
> Toni
> ________________________________________________________________
>      Were you helped on this list with your FreeNX problem?
>     Then please write up the solution in the FreeNX Wiki/FAQ:
> 
> 
http://openfacts2.berlios.de/wikien/index.php/BerliosProject:FreeNX_-_FAQ
> 
>          Don't forget to check the NX Knowledge Base:
>                  http://www.nomachine.com/kb/ 
> 
> ________________________________________________________________
>        FreeNX-kNX mailing list --- FreeNX-kNX at kde.org
>       https://mail.kde.org/mailman/listinfo/freenx-knx
> ________________________________________________________________
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.kde.org/pipermail/freenx-knx/attachments/20100518/7f68e038/attachment.html>