[Cialug] X11 applications over SSH very slow to start

[Daniel A. Ramaley]

I have a Debian Testing server that i'm SSH'ing to. The box is on a LAN 
with gigabit ethernet, so the network is nice and fast. SSH login is 
very fast. X11 applications, once started, perform very fast. The 
problem is that X11 applications are *very* slow to start. By "very" i 
mean from when i run a command there will be a 5 to 15 *minute* delay 
before the application appears. Once started, however, everything is 
nice and fast as one would expect on a gigabit LAN.

I tried setting "UseDNS no" in sshd_config on the server and restarting; 
no effect.

I tried SSH'ing with "-vvv". Here's the debug output i get when running 
an X11 program (emacs, but i don't think that matters since all X11 
applications seem to be affected):


debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 42410
debug2: fd 7 setting O_NONBLOCK
debug3: fd 7 is O_NONBLOCK
debug1: channel 1: new [x11]
debug1: confirm x11
debug2: channel 1: rcvd eof
debug2: channel 1: output open -> drain
debug2: channel 1: obuf empty
debug2: channel 1: close_write
debug2: channel 1: output drain -> closed
debug1: channel 1: FORCE input drain
debug2: channel 1: ibuf empty
debug2: channel 1: send eof
debug2: channel 1: input drain -> closed
debug2: channel 1: send close
debug3: channel 1: will not send data after close
debug2: channel 1: rcvd close
debug3: channel 1: will not send data after close
debug2: channel 1: is dead
debug2: channel 1: garbage collecting
debug1: channel 1: free: x11, nchannels 2
debug3: channel 1: status: The following connections are open:
  #0 client-session (t4 r0 i0/0 o0/0 fd 4/5 cc -1)
  #1 x11 (t4 r3 i3/0 o3/0 fd 7/7 cc -1)

debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 42412
debug2: fd 7 setting O_NONBLOCK
debug3: fd 7 is O_NONBLOCK
debug1: channel 1: new [x11]
debug1: confirm x11
debug2: channel 1: rcvd eof
debug2: channel 1: output open -> drain
debug2: channel 1: obuf empty
debug2: channel 1: close_write
debug2: channel 1: output drain -> closed
debug1: channel 1: FORCE input drain
debug2: channel 1: ibuf empty
debug2: channel 1: send eof
debug2: channel 1: input drain -> closed
debug2: channel 1: send close
debug3: channel 1: will not send data after close
debug2: channel 1: rcvd close
debug3: channel 1: will not send data after close
debug2: channel 1: is dead
debug2: channel 1: garbage collecting
debug1: channel 1: free: x11, nchannels 2
debug3: channel 1: status: The following connections are open:
  #0 client-session (t4 r0 i0/0 o0/0 fd 4/5 cc -1)
  #1 x11 (t4 r3 i3/0 o3/0 fd 7/7 cc -1)

debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 42414
debug2: fd 7 setting O_NONBLOCK
debug3: fd 7 is O_NONBLOCK
debug1: channel 1: new [x11]
debug1: confirm x11
debug1: client_input_channel_open: ctype x11 rchan 4 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 42416
debug2: fd 8 setting O_NONBLOCK
debug3: fd 8 is O_NONBLOCK
debug1: channel 2: new [x11]
debug1: confirm x11
debug2: channel 2: rcvd eof
debug2: channel 2: output open -> drain
debug2: channel 2: obuf empty
debug2: channel 2: close_write
debug2: channel 2: output drain -> closed
debug1: channel 2: FORCE input drain
debug2: channel 2: ibuf empty
debug2: channel 2: send eof
debug2: channel 2: input drain -> closed
debug2: channel 2: send close
debug3: channel 2: will not send data after close
debug2: channel 2: rcvd close
debug3: channel 2: will not send data after close
debug2: channel 2: is dead
debug2: channel 2: garbage collecting
debug1: channel 2: free: x11, nchannels 3
debug3: channel 2: status: The following connections are open:
  #0 client-session (t4 r0 i0/0 o0/0 fd 4/5 cc -1)
  #1 x11 (t4 r3 i0/0 o0/0 fd 7/7 cc -1)
  #2 x11 (t4 r4 i3/0 o3/0 fd 8/8 cc -1)


After about 6 or 7 minutes and all of those debug lines, then emacs 
finally opened. Any ideas?

__
Daniel A. Ramaley
Network Engineer 2

Dial Center 112, Drake University
2407 Carpenter Ave / Des Moines IA 50311 USA
Tel: +1 515 271-4540
Fax: +1 515 271-1938
E-mail: daniel.ramaley at drake.edu