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List:       kde-bugs-dist
Subject:    [kwin] [Bug 348206] New: KWin CPU usage rises when mplayer is playing a video
From:       Mark <markg85 () gmail ! com>
Date:       2015-05-25 14:36:33
Message-ID: bug-348206-17878 () http ! bugs ! kde ! org/
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https://bugs.kde.org/show_bug.cgi?id=348206

            Bug ID: 348206
           Summary: KWin CPU usage rises when mplayer is playing a video
           Product: kwin
           Version: unspecified
          Platform: Compiled Sources
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: core
          Assignee: kwin-bugs-null@kde.org
          Reporter: markg85@gmail.com

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

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