Arch Linux

mouseman

Member

From: Outta nowhere

Registered: 2014-04-04

Posts: 298

[Solved] X11Forwarding over SSH extremely slow

There is so much about the subject to be found but almost all of it (what I could find) applies to bandwitdh limitations, compression or encryption cipher.

The problem is that when I start an X application remotely, it takes minutes (yes, minutes) to just draw the window. When I was troubleshooting yesterday I tried compression and different ciphers, including aes128-cbc which I believe is hardware accellerated on newer i5 and i7 CPU's but nothing really mattered.

I'm ssh'ing to a local machine over wired gigabit network.

Last night I enabled these on the server, they were commented out:
X11DisplayOffset 10
X11UseLocalhost no

And restarted sshd. And while I didn't understand why, it was suddenly working fast. I could start virtualbox and work with VM's like it was running locally. In retrospect, it must have been something else because today, everything is slow again and no settings have changed.

When I start virtualbox for instance, I am getting these messages:

Qt WARNING: X Error: BadAccess (attempt to access private resource denied) 10
  Major opcode: 2 (X_ChangeWindowAttributes)
  Resource id:  0xac
Xlib:  extension "SYNC" missing on display "localhost:10.0".
Qt WARNING: libpng warning: iCCP: known incorrect sRGB profile

I searched for these errors and warnings, I believe the iCCP message is harmless but the other 2 I have no idea about. Searching finds some obscure stuff that doesn't seem helpful to me in my case.

Does anyone have any idea what is causing things to be so incredibly slow?

Thanks in advance!

For reference, sshd_config on the server:
<snip>

Edit:
The NIC in the server is acting up, I noticed speed dropping to kb/s. Luckily it has 2 NIC's onboard and the other one works without trouble.

Last edited by mouseman (2015-03-29 12:25:15)