[Bug 1592668] [NEW] plasmashell is eating 100% cpu and all UI is slow

[DimanNe]

Public bug reported:

plasmashell (and Xorg) processes have recently started to eat 100% cpu
and all UI operations are VERY slow now.

Some info from perf top:

Annotate _Z7qstrcmpRK10QByteArrayPKc
Zoom into plasmashell(2412) thread
Zoom into libQt5Core.so.5.5.1 DSO
Browse map details
Run scripts for samples of thread [plasmashell]
Run scripts for samples of symbol [_Z7qstrcmpRK10QByteArrayPKc]

Plasmashell thread
http://pastebin.com/CZtfCq7m

Xorg thread
http://pastebin.com/eAi9Ua9N

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: plasma-workspace 4:5.5.5.2-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-24.43-generic 4.4.10
Uname: Linux 4.4.0-24-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: KDE
Date: Wed Jun 15 09:50:25 2016
InstallationDate: Installed on 2012-11-28 (1294 days ago)
InstallationMedia: Kubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.1)
JournalErrors:
 Error: command ['journalctl', '-b', '--priority=warning', '--lines=1000'] failed with exit code 1: Hint: You are currently not seeing messages from other users and the system.
       Users in the 'systemd-journal' group can see all messages. Pass -q to
       turn off this notice.
 No journal files were opened due to insufficient permissions.
SourcePackage: plasma-workspace
UpgradeStatus: Upgraded to xenial on 2016-04-22 (53 days ago)

** Affects: plasma-workspace (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug xenial

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https://bugs.launchpad.net/bugs/1592668

Title:
  plasmashell is eating 100% cpu and all UI is slow

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