Hi, I was playing a video in mplayer with the system monitor up. The case for that was observing mplayer cpu usage to determine if hardware accelerated decoding was working (it was). While doing that i noticed kwin going up in CPU usage. Only up to 1 percent so it's still nothing to worry about, but it does "point" to something in the kwin code that is running quite heavily while.. watching a video with mplayer.. I don't see a relation there so kwin might be doing something it doesn't need to do. So i ran kwin through callgrind (via valgrind) to figure out what's going on here. I didn't have debug symbols for the full frameworks/plasma/qt stack, just for kwin, so my findings might not expose the actual issue, but they will point in the direction of it. It looks like QObject::property is being called very often when opening an mplayer window. This property is being called (in a cycle) in kwineffects.cpp. The top callers of QObject::property are: - KWin::EffectWindow::pos - KWin::EffectWindow::isDesktop - KWin::EffectWindow::hasAlpha - KWin::EffectWindow::opacity - KWin::EffectWindow::isDeleted - KWin::EffectWindow::contentsRect What is going on here? Why are these methods (among a lot of others, but they call QObject::property less) being called in a cycle for mplayer, but not for - for instance - dolphin? One thing that's very important to notice when you decide to debug and fix this. The kwin cpu usage only goes up to 1% (and stays there) when _playing_ a video. Just having the mplayer window with a video in pause will not make kwin hang on 1%. If you need more info, feel free to ask. Reproducible: Always
because the compositor needs to perform a repaint of the desktop scene ~24 times a second for the refreshing video? it's oc. restricted to the require portions and layers - but those needs to be figured. dolphin otoh. doesn't perform constant updates (unless you scroll the view all the time)
(In reply to Thomas Lübking from comment #1) > because the compositor needs to perform a repaint of the desktop scene ~24 > times a second for the refreshing video? > it's oc. restricted to the require portions and layers - but those needs to > be figured. > > dolphin otoh. doesn't perform constant updates (unless you scroll the view > all the time) Hmm, that makes sense :) Thank you for clearing that up.
btw, do you have the transparency effect enabled and configured to set inactive windows translucent? (otherwise i'd expect the ::property calls to be optimized away except in debug builds of Qt)
I have the Translucency effect enabled with the default settings. Qt is build in release mode (system Qt, Archlinux). KWin was build with release and debug symbols. So not a full debug build.