XDMCP / Gnome / KDE / Data transfer / GTK QT / Xorg extension

Jean-Francois Bouchard jean-francois.bouchard at idilia.com
Wed Nov 12 13:54:40 PST 2008


We are in process to migrate our Thin client to a new Linux install and
we are facing a problem :

Problem :
We experience very slow scroll speed (lets say, cat /var/log/messages)
in Gnome terminal via XDMCP. (1M file : 1.5 minute to display)

Prognostic :
We don't know exactly why this is happening. We suspect GTK/QT handling
of bitmap or vector to be a problem. This is maybe due to Xorg extension.

Observation :
* Under Konsole (KDE/QT3) we are able to display a 1M file in about 1.3
second (very smooth scrolling).
* Under Terminal (Gnome/GTK) we display the same file in a full screen
Terminal in about 1.5 minute.
* When displaying the text file via Konsole, the thin client receive
about 2Megs of data from the server.
* When displaying the text file via Terminal, the thin client receive
about 9 to 15Megs of data from the server.

Setup :
On the thin client we use ...
X Protocol Version 11, Revision 0, Release 7.1.1
Kernel 2.6.18-92.1.17.el5
Gnome 2.16
KDE 3.5

On the fat server ...
X Protocol Version 11, Revision 0, Release 6.8.2
Kernel 2.6.9-78.0.1.ELsmp
Gnome 2.8
KDE 3.3

Question :
We would like to know if this could be related to X protocol or the way
things are handled when drawing text ?
Note that we are able with Ubuntu 8.04 to get a better performance
(still, 10 times higher with Terminal then Konsole, but good (11 seconds).

Thank you in advance !

Jean-Francois Bouchard

Note in the log file on the thin client we see the following extension
loading :
(II) Loading /usr/lib/xorg/modules/extensions/libextmod.so
(II) Loading extension SHAPE
(II) Loading extension BIG-REQUESTS
(II) Loading extension SYNC
(II) Loading extension MIT-SCREEN-SAVER
(II) Loading extension XC-MISC
(II) Loading extension XFree86-VidModeExtension
(II) Loading extension XFree86-Misc
(II) Loading extension XFree86-DGA
(II) Loading extension DPMS
(II) Loading extension TOG-CUP
(II) Loading extension Extended-Visual-Information
(II) Loading extension XVideo
(II) Loading extension XVideo-MotionCompensation
(II) Loading extension X-Resource
(II) Loading /usr/lib/xorg/modules/extensions/libdbe.so
(II) Loading extension DOUBLE-BUFFER
(II) Loading /usr/lib/xorg/modules/extensions/libglx.so
(II) Loading extension GLX
(II) Loading /usr/lib/xorg/modules/extensions/librecord.so
(II) Loading extension RECORD
(II) Loading /usr/lib/xorg/modules/extensions/libdri.so
(II) Loading extension XFree86-DRI
(II) Initializing built-in extension MIT-SHM
(II) Initializing built-in extension XInputExtension
(II) Initializing built-in extension XTEST
(II) Initializing built-in extension XKEYBOARD
(II) Initializing built-in extension XC-APPGROUP
(II) Initializing built-in extension SECURITY
(II) Initializing built-in extension XINERAMA
(II) Initializing built-in extension XFIXES
(II) Initializing built-in extension XFree86-Bigfont
(II) Initializing built-in extension RENDER
(II) Initializing built-in extension RANDR
(II) Initializing built-in extension COMPOSITE
(II) Initializing built-in extension DAMAGE
(II) Initializing built-in extension XEVIE


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