+ <div class="entry">
+ <div class="title"><a href="http://people.skolelinux.org/pere/blog/Why_the_KDE_menu_is_slow_when__usr__is_NFS_mounted___and_a_workaround.html">Why the KDE menu is slow when /usr/ is NFS mounted - and a workaround</a></div>
+ <div class="date"> 6th April 2012</div>
+ <div class="body"><p>Recently I have spent time with
+<a href="http://www.slxdrift.no/">Skolelinux Drift AS</a> on speeding
+up a <a href="http://www.skolelinux.org/">Debian Edu / Skolelinux</a>
+Lenny installation using LTSP diskless workstations, and in the
+process I discovered something very surprising. The reason the KDE
+menu was responding slow when using it for the first time, was mostly
+due to the way KDE find application icons. I discovered that showing
+the Multimedia menu would cause more than 20 000 IP packages to be
+passed between the LTSP client and the NFS server. Most of these were
+
+NFS LOOKUP calls, resulting in a NFS3ERR_NOENT response. Because the
+ping times between the client and the server were in the range 2-20
+ms, the menus would be very slow. Looking at the strace of kicker in
+Lenny (or plasma-desktop i Squeeze - same problem there), I see that
+the source of these NFS calls are access(2) system calls for
+non-existing files. KDE can do hundreds of access(2) calls to find
+one icon file. In my example, just finding the mplayer icon required
+around 230 access(2) calls.</p>
+
+<p>The KDE code seem to search for icons using a list of icon
+directories, and the list of possible directories is large. In
+(almost) each directory, it look for files ending in .png, .svgz, .svg
+and .xpm. The result is a very slow KDE menu when /usr/ is NFS
+mounted. Showing a single sub menu may result in thousands of NFS
+requests. I am not the first one to discover this. I found a
+<a href="https://bugs.kde.org/show_bug.cgi?id=211416">KDE bug report
+from 2009</a> about this problem, and it is still unsolved.</p>
+
+<p>My solution to speed up the KDE menu was to create a package
+kde-icon-cache that upon installation will look at all .desktop files
+used to generate the KDE menu, find their icons, search the icon paths
+for the file that KDE will end up finding at run time, and copying the
+icon file to /var/lib/kde-icon-cache/. Finally, I add symlinks to
+these icon files in one of the first directories where KDE will look
+for them. This cut down the number of file accesses required to find
+one icon from several hundred to less than 5, and make the KDE menu
+almost instantaneous. I'm not quite sure where to make the package
+publicly available, so for now it is only available on request.</p>
+
+<p>The bug report mention that this do not only affect the KDE menu
+and icon handling, but also the login process. Not quite sure how to
+speed up that part without replacing NFS with for example NBD, and
+that is not really an option at the moment.</p>
+
+<p>If you got feedback on this issue, please let us know on debian-edu
+(at) lists.debian.org.</p>
+</div>
+ <div class="tags">
+
+
+ Tags: <a href="http://people.skolelinux.org/pere/blog/tags/debian edu">debian edu</a>, <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>.
+
+
+ </div>
+ </div>
+ <div class="padding"></div>
+
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