[spread] workspace switcher performance is poor, especially on low powered CPUs

[Florian Boucault]

TBD

[Florian Boucault (fboucault)]

Profiling shows the following distribution of time spent at startup of the spread:

35%
jpeg loading (in GnomeBackground?)

15.10%
QGraphicsViewPrivate::updateInputMethodSensitivity() and _XimParseStringFile
exactly that bug: https://bugs.launchpad.net/ubuntu/+source/libx11/+bug/681939
http://<email address hidden>/msg00523.html

~15%
QML Drawing with OpenGL backend

~10%
QML loading and items instantiation

5.39%
gtk_init

4.39%
_dl_lookup_symbol_x

0.94%
in wnck somewhere

0.85%
IconImageProvider (in Window.qml?)

[Florian Boucault (fboucault)]

Actions that have been tried to save a lot of CPU time when trying to bring the spread up:
- replace background loading by screenshoting nautilus window
- downscaling the screenshot of the windows when loading them
- remove need to load/unload window list
- make window override_redirect: view.setWindowFlags(Qt::X11BypassWindowManagerHint);

[Florian Boucault (fboucault)]

Note that the profiling in comment #1 was done with the OpenGL backend thus not showing what time is spent in drawing with the Raster backend which is likely to be much bigger.

[Florian Boucault (fboucault)]

Fixing this bug involves fixing https://bugs.launchpad.net/unity-2d/+bug/808716

[Florian Boucault (fboucault)]

Implementing action 1 will also fix bug https://bugs.launchpad.net/unity-2d/+bug/703574

[Florian Boucault (fboucault)]

Action 2 "downscaling the screenshot of the windows when loading them" has been submitted:
https://code.launchpad.net/~fboucault/unity-2d/spread_limit_sizes/+merge/84707

[Launchpad Janitor (janitor)]

This bug was fixed in the package unity-2d - 5.2.0-0ubuntu1

---------------
unity-2d (5.2.0-0ubuntu1) precise; urgency=low

  [ Didier Roche ]
  * New upstream release:
    - Select quicklist items with just one right click (LP: #688830)
    - Launcher - Dragging and dropping a running application in to the Trash
      should quit the application and (if the app is pinned to the Launcher)
      un-pin the application from the Launcher (LP: #870143)
    - Dash - "See more..." line should be base-aligned with section header
      (LP: #748101)
    - right click on the dash icon should display a list of the lenses
      (LP: #868452)
    - Top Bar - rename the "Desktop" title in the Top Bar (displayed when no
      window has focus) to "Ubuntu Desktop" (LP: #869873)
    - Application title on quicklist should be bold (or more visible)
      (LP: #900400)
    - unity-2d-launcher crashed with SIGSEGV when opening a folder on a CD
      (LP: #831868)
    - unity-2d-places crashed with SIGSEGV in QScriptValue::call()
      (LP: #836498)
    - unity-2d-launcher crashed with SIGSEGV in geis_finish() (LP: #850893)
    - unity-2d-places crashed with SIGABRT in raise() (LP: #857575)
    - unity-2d-launcher crashed with SIGSEGV in exit() (LP: #859596)
    - [spread] layout broken since bzr revision 799 of lp:unity-2d
      (LP: #900895)
    - [workspace switcher] keyboard navigation of workspace switcher broken
      for accessibility (LP: #744978)
    - [spread] workspace switcher performance is poor, especially on low
      powered CPUs (LP: #745764)
    - Launcher - the rendering of the BFB and Lens squircle does not match the
      design (LP: #838708)
    - [dash] Huge performance hit when scrolling search results with
      accessibility enabled (LP: #862956)
    - DBUS_STARTER_ADDRESS and DBUS_STARTER_BUS_TYPE aren't always unset from
      environment making gedit and possibly others fail to start (LP: #873027)
    - Win Key can not be disabled in Unity-2d (LP: #873580)
    - [dash] Unity-2d dash very slow to open (LP: #881756)
    - [tests] LauncherViewTest hanging (LP: #894380)
    - [tests] Unit tests failing due to lack of Xserver (LP: #894381)
    - [launcher] Alt+F1 broken: does not give the focus to the launcher's
      content (LP: #901505)
    - [tests] Add Automated User Experience testing (LP: #903495)
    - [workspace switcher] Performance can be poor when using the opengl
      backend because of window texture sizes that are not limited
      (LP: #808716)
    - [dash] no way to unmaximize (LP: #860400)
    - [launcher] In non-composite mode, background is black (LP: #879288)
    - [dash] Unity 2D shows 'Search' instead of 'Run Command' on ALT + F2
      (LP: #883392)
    - [launcher] Removing icon from launcher makes it hide immediately
      (LP: #884410)
    - OpenGL disabled regardless of use-opengl setting (LP: #887957)
    - if libdir does not equal lib (LP: #888164)
    - [launcher] Launcher stuck open while mouse moved to left corner of panel
      (LP: #892004)
    - [dash] Long results label are truncated instead of elided and a few
      pixels of the next line is visible (LP: #901491)
    - [launcher] Dash icon missing...