X Forwarding Much Slower on Hardy than Gutsy (ssh and telnet)

[Cornelius Brinegar]

I have machines running both recent Ubuntu releases (7.10 and 8.04), and when I ssh -X to the machines with Hardy Heron (8.04 AKA HH) GUI programs are not as responsive as they are with Gutsy Gibbon (7.10 AKA GG). Below is a summary of the behavior:

Slow:
ssh -X from GG to HH
ssh -X from HH to HH
ssh -X from HH to itself

Fast:
ssh -X from GG to another GG
ssh -X from GG to itself
ssh -X from HH to GG

The behavior is that scrolling, typing, and mouse clicks are not very responsive. Running the applications tested by sitting at the machines (not through ssh) results in normal operation. The applications tested have been Matlab, gvim, and gedit, and I don't believe the problem is specific to any of those programs. All of these ssh combinations should be quite fast, but any that does a ssh to one of 3 machines running HH has a slow GUI experience.

The same behavior exists when connecting using telnet (temporarily installed for testing). Also, internet speed tests show that both the GG and HH machines have very similar upload and download speeds, and all the machines are on a fast local network. And no significant background processes are running.

The problem is severe enough for me to revert back to GG (7.10) on my group's server so that it is possible to edit and execute MATLAB code efficiently through a ssh connection. The connection is now as fast as expected.

I have searched through Google, the Ubuntu forums, and Launchpad for duplicate bugs but have not found anything like this yet. Also, this is not the same issue where users were experiencing a slow request for a password. (I did post this issue in the forum with username cbrinegar.) The closest reports I have found are listed below:
https://bugs.launchpad.net/ubuntu/+source/tracker/+bug/229563

[oliford (oliford)]

I've recently upgraded to hardy and am also seeing this.

It also occurs if you enable TCP access to the xserver, set DISPLAY on another machine and use the hardy X-server directly.

[oliford (oliford)]

To clarify that a bit:
Running a program on a Gutsy machine displaying on an open Hardy X-Server is fast.
Running a program on a Hardy machine displaying on an open Gutsy X-Server is slow.
Running a program on a Hardy machine displaying on an open Hardy X-Server is slow.
(We only have 1 gutsy machine left)

This is after turning off 'Applications->Settings->Login Window->Deny TCP connections to x server' and running 'xhost +' to disable access control.
Tested with simple 'plot()' command in scilab.

[Jochen Schulz (schulz-math)]

It seems i have exactly the same problem. We use Matlab intensivly via ssh (and X-forwarding), but after upgrading to ubuntu hardy 8.04 it is really slow and nearly unusable in a daily matter. We circumvent the problem via using vnc client/server, but this solution is somewhat less flexible.

[oliford (oliford)]

This bug is still present in Intrepid. I had hoped the new version of X would have sorted it out, but no.

This was both connecting into Interpid from Hardy and vice versa.

[Alex Meakins (alex-meakins)]

I see exactly the same behaviour with both Hardy and Intrepid. This really does need to be fixed.

[oliford (oliford)]

I've found a workaround for this myself by simply dropping back to the gutsy X11 client library (/usr/lib/libX11.so.6).
Just get a copy of that library from gutsy and put it on your (in my case intrepid) machine under a different directory. Then put that directory in the library path eg:

mkdir /root/fixTheXClient
cp -Pv gutsymachine/usr/lib/libX11* /root/fixTheXClient

Then whenever you want to run a program with sensible speed graphics:
export LD_LIBRARY_PATH=/root/fixTheXClient:$LD_LIBRARY_PATH
{run your program}

You can check it's going to use the right one with:
ldd {your_program}

[Johannes Karlsson (johk)]

I have the same problem as described here.

The workaround, described by oliford, works for me as well. Thanks!

This thread seems to deal with a similar problem in Fedora 7 and onward:
http://www.mathworks.ch/matlabcentral/newsreader/view_thread/244711

It is suggested that building libX11 without xcb solves the problem. I haven't been able to try if this fixes the problem in Ubuntu as well.

[Thomas Smith (tgs-resc)]

A less hacky way of getting the non-xcb version of libX11-6 is to install older versions of the packages. Look for Martey Dodoo's comment in:

https://bugs.launchpad.net/ubuntu/+source/xcb/+bug/88815

I use VNC to connect to a server where I use Matlab and other programs. Upgrading the server from 7.10 Gutsy to 8.04 Hardy made everything terribly slow over VNC. Downgrading the libX11-6 packages to the ones given above sped up everything except Matlab, which is still unusably slow. *sigh*

[Thomas Smith (tgs-resc)]

This is still a problem in Jaunty, with libx11-6 version 2:1.1.99.2-1ubuntu2. Again, downgrading to libx11-6 and libx11-dev version 2:1.0.3-4ubuntu1 from Feisty fixed the problem.

https://launchpad.net/ubuntu/feisty/amd64/libx11-6

Any progress on fixing this? I have had no problems with anything needing XCB but not getting it, can't we just have a clean, non-slow version?

[oliford (oliford)]

This bug has finally gone away.

It definately works in lucid (fortunately, because downgrading libx11 causes too many other problems). I think it works fine in karmic too.

[smithfarm (presnypreklad)]

I'm running karmic and this bug bit me bad.