Version:           4.8.0 (using Devel) 
OS:                Linux

After upgrade to KDE 4.8 beta 1 (and now in beta 2) I noticed that after some time is the kwin cpu usage more then 20% even there are no effects running. Restart of kwin (kwin --replace) decrease kwin cpu usage to 0-2%. After some time, kwin cpu usage again more than 20%.

Reproducible: Always

Steps to Reproduce:
1) Work as usual and monitor kwin cpu usage.
2) When is kwin cpu usage high, restart kwin (ALT+F2 and kwin --replace)
3) Kwin cpu usage is low again.

Actual Results:  
Kwin uses about 20% of cpu after some time (hour and more). Even there is nothing to do - no effects active.

Expected Results:  
Kwin cpu usage should be minimal when nothing happen.

$ LANG=C kwin -v
Qt: 4.7.4
KDE Development Platform: 4.7.90 (4.8 Beta2 (4.7.90)
KWin: 4.7.90 (4.8 Beta2 (4.7.90)

GK: nVidia Corporation G98M [Quadro NVS 160M]
driver: [I] x11-drivers/nvidia-drivers (290.10@1.12.2011)

OpenGL composition enabled, OpenGL2 shaders and vertical synchronisation enabled.

$ cat kwinrc
[$Version]
update_info=kwin_remove_effects.upd:kwin4.7_effects

[Compositing]
AnimationSpeed=3
Backend=OpenGL
CheckIsSafe=true
DisableChecks=false
Enabled=true
GLDirect=true
GLLegacy=false
GLMode=SHM
GLTextureFilter=2
GLVSync=true
HiddenPreviews=5
OpenGLIsUnsafe=false
UnredirectFullscreen=true
XRenderSmoothScale=false

[Desktops]
Name_1=
Name_2=
Name_3=
Name_4=
Number=4

[Effect-BoxSwitch]
TabBox=false
TabBoxAlternative=false

[Effect-CoverSwitch]
TabBox=false

[Effect-Cube]
BackgroundColor=0,0,0
BorderActivate=9
BorderActivateCylinder=9
BorderActivateSphere=9
CapColor=197,197,197
CapDeformation=50
Caps=true
CloseOnMouseRelease=false
DisplayDesktopName=true
InvertKeys=false
InvertMouse=false
Opacity=80
OpacityDesktopOnly=false
Reflection=true
RotationDuration=0
TabBox=false
TexturedCaps=true
Wallpaper=
ZOrdering=true
ZPosition=100

[Effect-DesktopGrid]
BorderActivate=9

[Effect-FlipSwitch]
BorderActivate=9
BorderActivateAll=9
TabBox=false

[Effect-PresentWindows]
BorderActivate=9
BorderActivateAll=7
TabBox=true

[ElectricBorders]
Bottom=None
BottomLeft=None
BottomRight=None
Left=None
Right=None
Top=None
TopLeft=None
TopRight=None

[Plugins]
kwin4_effect_blurEnabled=false
kwin4_effect_boxswitchEnabled=false
kwin4_effect_coverswitchEnabled=false
kwin4_effect_cubeEnabled=false
kwin4_effect_cubeslideEnabled=false
kwin4_effect_dashboardEnabled=true
kwin4_effect_desktopgridEnabled=true
kwin4_effect_dialogparentEnabled=true
kwin4_effect_diminactiveEnabled=false
kwin4_effect_dimscreenEnabled=true
kwin4_effect_explosionEnabled=false
kwin4_effect_fadeEnabled=false
kwin4_effect_fadedesktopEnabled=false
kwin4_effect_fallapartEnabled=false
kwin4_effect_flipswitchEnabled=false
kwin4_effect_glideEnabled=true
kwin4_effect_highlightwindowEnabled=false
kwin4_effect_invertEnabled=false
kwin4_effect_loginEnabled=true
kwin4_effect_logoutEnabled=true
kwin4_effect_lookingglassEnabled=false
kwin4_effect_magiclampEnabled=false
kwin4_effect_magnifierEnabled=false
kwin4_effect_minimizeanimationEnabled=true
kwin4_effect_mousemarkEnabled=false
kwin4_effect_outlineEnabled=true
kwin4_effect_presentwindowsEnabled=true
kwin4_effect_resizeEnabled=false
kwin4_effect_scaleinEnabled=false
kwin4_effect_screenshotEnabled=true
kwin4_effect_sheetEnabled=false
kwin4_effect_showfpsEnabled=false
kwin4_effect_showpaintEnabled=false
kwin4_effect_slideEnabled=true
kwin4_effect_slidebackEnabled=false
kwin4_effect_slidingpopupsEnabled=true
kwin4_effect_snaphelperEnabled=false
kwin4_effect_startupfeedbackEnabled=true
kwin4_effect_taskbarthumbnailEnabled=true
kwin4_effect_thumbnailasideEnabled=false
kwin4_effect_trackmouseEnabled=false
kwin4_effect_translucencyEnabled=true
kwin4_effect_windowgeometryEnabled=false
kwin4_effect_wobblywindowsEnabled=true
kwin4_effect_zoomEnabled=false

[PopupInfo]
PopupHideDelay=1000
ShowPopup=false
TextOnly=false

[Style]
BorderSize=1
ButtonsOnLeft=MSF
ButtonsOnRight=HIAX
CustomButtonPositions=true
PluginLib=kwin3_oxygen
ShowToolTips=true

[SubSession: 11b8bc33-3c70-48e0-8173-79d17423ae4f]
active=-1
count=0

[SubSession: c37db738-92cd-459e-a174-d003feb33b94]
active=-1
count=0

[SubSession: fd198773-dd85-40a1-ac75-39f66fb73723]
active=-1
count=0

[Windows]
ActiveMouseScreen=false
AutoRaise=false
AutoRaiseInterval=750
AutogroupInForeground=false
AutogroupSimilarWindows=false
ClickRaise=true
DelayFocus=false
DelayFocusInterval=0
ElectricBorderCooldown=350
ElectricBorderDelay=150
ElectricBorderMaximize=true
ElectricBorderTiling=true
ElectricBorders=2
FocusPolicy=ClickToFocus
FocusStealingPreventionLevel=2
HideUtilityWindowsForInactive=true
InactiveTabsSkipTaskbar=false
Placement=Smart
RollOverDesktops=false
SeparateScreenFocus=false
ShadeHover=false
ShadeHoverInterval=250
TilingDefaultLayout=0
TilingOn=false
TilingRaisePolicy=0