[Bug 1572939] [NEW] X11 forwarding slows down client

[Karl-Philipp Richter]

Public bug reported:

X11 forwarding slows down Ubuntu 16.04 with Unity desktop whose whole
graphic interface (including mouse pointer) repeatedly becomes
unresponsive for seconds if `ssh -X` or `ssh -X -C` is used. The
symptoms are the same as if the system were using slow swap space which
isn't the case (verified with `htop` in another tty which can still be
changed). This wasn't the case in previous unknown versions.

experienced with 1:6.9p1-2ubuntu0.1 on Ubuntu 15.10,
V_7_1_P1-171-g4c6cb83 source installation and 1:7.2p2-4 on Ubuntu 16.04

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ssh 1:7.2p2-4
Uname: Linux 4.5.0-040500-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Apr 21 12:19:12 2016
InstallationDate: Installed on 2015-12-12 (130 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
PackageArchitecture: all
SourcePackage: openssh
UpgradeStatus: Upgraded to xenial on 2016-03-14 (37 days ago)

** Affects: openssh (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug xenial

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https://bugs.launchpad.net/bugs/1572939

Title:
  X11 forwarding slows down client

Status in openssh package in Ubuntu:
  New

Bug description:
  X11 forwarding slows down Ubuntu 16.04 with Unity desktop whose whole
  graphic interface (including mouse pointer) repeatedly becomes
  unresponsive for seconds if `ssh -X` or `ssh -X -C` is used. The
  symptoms are the same as if the system were using slow swap space
  which isn't the case (verified with `htop` in another tty which can
  still be changed). This wasn't the case in previous unknown versions.

  experienced with 1:6.9p1-2ubuntu0.1 on Ubuntu 15.10,
  V_7_1_P1-171-g4c6cb83 source installation and 1:7.2p2-4 on Ubuntu
  16.04

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: ssh 1:7.2p2-4
  Uname: Linux 4.5.0-040500-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Thu Apr 21 12:19:12 2016
  InstallationDate: Installed on 2015-12-12 (130 days ago)
  InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
  PackageArchitecture: all
  SourcePackage: openssh
  UpgradeStatus: Upgraded to xenial on 2016-03-14 (37 days ago)

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