GNOME via remote X server - slow root window redraw

[Toralf Lund]

John Summerfied wrote:

> Toralf Lund wrote:
>
>> Hi.
>>
>> I though I might forward a question of mine that got no response on 
>> the mailing list:
>
That should be "the GNOME mailing list"...

>>
>>> Another thing I thought would be fun to try on my new Mini Mac: I'm
>>> logging into GNOME on my FC3 box via XDMCP (on the Fedora host) and 'X
>>> -broadcast' (on the Mac.)  [ ... ]
>>>
>>> - Toralf
>>
>>
>>
>> Actually, the problem could be that the connection just isn't fast 
>> enough for smooth image data display; I'm using an 11Mb wireless 
>> link, which I now think is quite a bit slower in real terms even than 
>> 10Mb UTP Ethernet. However, the operation is just as slow with a 
>> plain-colour background as it is when using an image. Does this mean 
>> that raw pixel data is sent to the display even in the former mode? Why?
>
>
> I've used X -query to login to several different machines on my 100 
> mbit LAN. There was some slight slowness compared with X on the same 
> box, but nothing of concern.

I think that's pretty much the conclusion I reached, too, when I did 
similar things on the LAN at work earlier, but it's been a long time 
since I used a setup like that there.

>
> I have used VNC over dialup as recently as today, and I found a 
> 1024x768 usable. Not great, but usable. "X -query" would not be a goer 
> over a modem.

I guess not. Although *some* operations would probably be faster via X 
-query. The way I understand it, VNC is in some ways more demanding on 
bandwith because everything is essentially transferred in terms of pixel 
data, while with X, certain "large" operations might be encoded as 
high-level commands requiring next to nothing from the network. On the 
other hand, VNC seems to transfer pixels in a much more efficient manner 
than X, so it you end up doing image data operations after all, VNC is 
probably better.

I've also thought about testing LBX (low bandwidth X), but I'm not quite 
sure how to set it up. I mean, the documentation explains the low-level 
architecture in great detail, but it's not obvious from reading it (to 
me at least) how it all fits together. I mean, how exactly do I set it 
up so that a user may run a full logion session from a remote X server?

>
>
> Note that the usability of VNC or X over a network depends on what 
> one's doing. _I_ was mostly typing into xterms and the like, with a 
> bit of mozzie mail reading. Playing games or movies would be another 
> thing altogether.
>
> I do not think Gnome a relevant part of your problem.

Well, maybe not to a great extent, but the performance does seem to be 
influenced by the implementation of the desktop background draw 
routines, which surely depend on the actualy environment used. I suspect 
that GNOME uses low-level pixel data operations where higher-level 
drawing routines would be a lot more efficient, i.e. that it uses 
XPutImage() instead of XFillRectangle() or whatever...

- Toralf