Recently I have spent time with +Skolelinux Drift AS on speeding +up a Debian Edu / Skolelinux +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.
+ +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 +KDE bug report +from 2009 about this problem, and it is still unsolved.
+ +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.
+ +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.
+ +If you got feedback on this issue, please let us know on debian-edu +(at) lists.debian.org.
+ +