[Bug 877538] [NEW] kwin is slow with raster rendering & compositing disabled

[S. Christian Collins]

Public bug reported:

Since upgrading from Kubuntu 11.04 (KDE 4.6.2, Xorg 1.10.1, xserver-xorg
v7.6 kernel 2.6.38-11) to Kubuntu 11.10 (KDE 4.7.1, Xorg 1.10.4,
xserver-xorg v7.6, kernel 3.0.0-12), I have noticed a severe drop in
kwin performance when drawing changes to the window decorations.  The
slowness can be observed when new windows are created (the decorations
are slow to be created) and when windows become active or inactive (the
decorations are slow to change between active/inactive state).

Since I have been able to reproduce this problem on systems with both
Intel and NVIDIA graphics cards, I don't believe this bug to be graphics
driver-related.  The issue does not seem tied to any particular Kwin
theme either.

Please see the following YouTube video for a demonstration:
http://www.youtube.com/watch?v=MUSRzUyjXY0

The slowness goes away when kwin is switched to "native" rendering
instead of the default "raster".  According to the related KDE bug
report (https://bugs.kde.org/show_bug.cgi?id=284291), this will be fixed
in KDE 4.8.  However, the question for Kubuntu is whether or not kwin
should be set to "raster" or "native" rendering by default.

Steps to Reproduce:
This test can be reproduced easily using the Kubuntu 11.04 and 11.10 live CDs.  For best results, use a slower PC to do these tests:
1) Open Dolphin.
2) Click the desktop to make Dolphin an inactive window.  Click on Dolphin to
make it the active window.  You will observe a delay under Kubuntu 11.10 when
performing this step.  To see this effect easier, you may want to disable
animations and enable "outline active window title" in the Oxygen decoration
settings.
3) From Dolphin's "Help" menu, select "About Dolphin".  When the about window
appears, you will see the window decoration sluggish to appear around the
newly-created window contents.

Workaround:
Those affected by this bug can run the following command:
    kwin --replace --graphicssystem=native

If the kwin performance improves, you can make the setting permanent by creating the following script as /usr/local/bin/kwin-native:
    #!/bin/bash
    kwin --graphicssystem=native

Then, add the following to /etc/profile:
    export KDEWM="kwin-native"

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

-- 
You received this bug notification because you are a member of Kubuntu
Bugs, which is subscribed to kde-workspace in Ubuntu.
https://bugs.launchpad.net/bugs/877538

Title:
  kwin is slow with raster rendering & compositing disabled

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/kde-workspace/+bug/877538/+subscriptions