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List:       kwin
Subject:    Re: kwin performance
From:       Lubos Lunak <l.lunak () suse ! cz>
Date:       2009-10-13 16:00:42
Message-ID: 200910131800.42835.l.lunak () suse ! cz
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On Friday 09 of October 2009, Chris Vickery wrote:
> Hello,
> I've been doing some benchmarking on kwin from KDE4 versus kwin of KDE3...
> I'm doing these benchmarks over XDMCP as that is the environment I wish to
> get working. Right off the bat using kde4 it was obvious that window
> management was much slower, and the benchmarks proved it.

> I, currently, use kwin3 on my KDE4
> session and it's actually quite a nice experience -- XDMCP sessions are not
> far off for KDE4, which means that KDE4 can be seen on a thin client pretty
> soon (which is my ultimate goal here).

 I think there are other facts for remote session than just the window manager 
performance, the applications themselves should perform well.

> So, my questions are as follows... Are there any configuration tweaks I can
> do to increase performance with kwin4? All visual effects are disabled
> right now. Also, does anyone know if there is a distinct part of kwin4 that
> makes it so much slower, and if so it would it be worth it/possible for me
> to hack though it and make a kwin4-light that has comparable performance to
> kwin3?

 What makes remote sessions slower are primarily roundtrips (i.e. the app 
requests something from the X server and synchronously waits for an answer). 
A second reason might be excessive amounts of data to transfer (e.g. if it 
would repeatedly do QImage->QPixmap transformations).

 There are tools for monitoring communication with the X server, e.g. xmon or 
xscope (IIRC the names). So the way to find the problems would be using one 
of these tools and identifying the places that do either of these expensive 
things - first running the tools to check which requests are often done in 
this way, then finding the places in code that cause them. It's not exactly 
simple and it's tedious - a way could be e.g. recompile Xlib and add 
basically a variant of kBacktrace() showing where the request comes from in 
KDE/Qt.

-- 
Lubos Lunak
KDE developer
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SUSE LINUX, s.r.o.   e-mail: l.lunak@suse.cz , l.lunak@kde.org
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Czech Republic       http://www.suse.cz
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