When profiling compiz/unity (during pulse animations) I noticed LauncherIcon::ColorForIcon was almost the single most expensive function (after malloc and free) in the compiz process. This didn't look right so I added some debug messages and found that it was SimpleLauncherIcon::GetTextureForSize repeatedly reloading (and reprocessing) some icons from scratch on every single redraw.
The cause is pretty obvious in SimpleLauncherIcon::GetTextureForSize. It assumes the loaded icon size is always exactly that of the desired icon size for the launcher. Obviously for most fixed sized icons this won't be true. So it reloads and reprocesses those icons on EVERY frame when redrawing the launcher.
Fixing the simple logic error in SimpleLauncherIcon::GetTextureForSize I found I could reduce compiz/unity CPU usage during animations (when the launcher is constantly redrawing) by up to 50%. And even a constant 25% improvement on my regular idle desktop. So definitely worth fixing.
ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: unity 3.8.16-0ubuntu1~natty1
ProcVersionSignature: Ubuntu 2.6.38-10.46-generic 2.6.38.7
Uname: Linux 2.6.38-10-generic x86_64
NonfreeKernelModules: fglrx
Architecture: amd64
CompizPlugins: [core,bailer,detection,composite,opengl,compiztoolbox,decor,vpswitch,place,imgpng,regex,unitymtgrabhandles,grid,session,snap,mousepoll,resize,move,animation,expo,ezoom,workarounds,resizeinfo,wall,staticswitcher,fade,scale,unityshell]
Date: Sun Aug 7 12:59:41 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
ProcEnviron:
LANGUAGE=en_AU:en
LANG=en_AU.UTF-8
SHELL=/bin/bash
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)
It seems a fix has already been committed to unity 4.x without a bug number:
http://