[X2Go-Dev] Bug#813: Performance drop using large virtual screen

[Hrvoje Habjanić]

Package: x2goserver
Version: 4.0.1.19-0~1062~ubuntu14.04.1

Hi.

I noticed that using large screens (bigger than 800x600) causes x2go to
start slowing down. Especially problematic are full-screen switches, for
example when you switch from one virtual screen to another, inside of
x2go virtual screen. This slow down is experienced as sudden session
freeze, depending on screen size, it can stall for up to few seconds.
After some time this becomes really annoying ...

This is not influenced by switching to different
encoding or line speed in GUI.

Eventually i did track down to cache sizes. In /usr/bin/x2gostartagent file
there is fixed cache size: "cache=8M,disk=32M".

Increasing this cache size completely removes this freeze, and also
significantly reduces session bandwidth! For example, with session
1680x1050, using 16bit RLE, changing cache to "64M" bandwidth drops
from 3-4Mbit/s down to ~200kbit/s! I also noticed better responsiveness
when using "disk=0".

So, it seems that default settings (cache=8M,disk=32M) are maybe too
small for todays use with lager virtual screens, and this should be
increased.
I would suggest using at least "cache=64M" as default.

Also, it would be nice to add a possibility to change those values in a nice
way, since directly editing the script is more like a hack. Also, when
script is
updated, changes are lost.

Regards,

H.