blog/Why_the_KDE_menu_is_slow_when__usr__is_NFS_mounted___and_a_workaround.html

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   6     <title>Petter Reinholdtsen: Why the KDE menu is slow when /usr/ is NFS mounted - and a workaround</title>
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  14  <h1>
  15      <a href="http://people.skolelinux.org/pere/blog/">Petter Reinholdtsen</a>
  16
  17  </h1>
  18
  19 </div>
  20
  21
  22     <div class="entry">
  23       <div class="title">Why the KDE menu is slow when /usr/ is NFS mounted - and a workaround</div>
  24       <div class="date"> 6th April 2012</div>
  25       <div class="body"><p>Recently I have spent time with
  26 <a href="http://www.slxdrift.no/">Skolelinux Drift AS</a> on speeding
  27 up a <a href="http://www.skolelinux.org/">Debian Edu / Skolelinux</a>
  28 Lenny installation using LTSP diskless workstations, and in the
  29 process I discovered something very surprising.  The reason the KDE
  30 menu was responding slow when using it for the first time, was mostly
  31 due to the way KDE find application icons.  I discovered that showing
  32 the Multimedia menu would cause more than 20 000 IP packages to be
  33 passed between the LTSP client and the NFS server.  Most of these were
  34
  35 NFS LOOKUP calls, resulting in a NFS3ERR_NOENT response.  Because the
  36 ping times between the client and the server were in the range 2-20
  37 ms, the menus would be very slow.  Looking at the strace of kicker in
  38 Lenny (or plasma-desktop i Squeeze - same problem there), I see that
  39 the source of these NFS calls are access(2) system calls for
  40 non-existing files.  KDE can do hundreds of access(2) calls to find
  41 one icon file.  In my example, just finding the mplayer icon required
  42 around 230 access(2) calls.</p>
  43
  44 <p>The KDE code seem to search for icons using a list of icon
  45 directories, and the list of possible directories is large.  In
  46 (almost) each directory, it look for files ending in .png, .svgz, .svg
  47 and .xpm.  The result is a very slow KDE menu when /usr/ is NFS
  48 mounted.  Showing a single sub menu may result in thousands of NFS
  49 requests.  I am not the first one to discover this.  I found a
  50 <a href="https://bugs.kde.org/show_bug.cgi?id=211416">KDE bug report
  51 from 2009</a> about this problem, and it is still unsolved.</p>
  52
  53 <p>My solution to speed up the KDE menu was to create a package
  54 kde-icon-cache that upon installation will look at all .desktop files
  55 used to generate the KDE menu, find their icons, search the icon paths
  56 for the file that KDE will end up finding at run time, and copying the
  57 icon file to /var/lib/kde-icon-cache/.  Finally, I add symlinks to
  58 these icon files in one of the first directories where KDE will look
  59 for them.  This cut down the number of file accesses required to find
  60 one icon from several hundred to less than 5, and make the KDE menu
  61 almost instantaneous.  I'm not quite sure where to make the package
  62 publicly available, so for now it is only available on request.</p>
  63
  64 <p>The bug report mention that this do not only affect the KDE menu
  65 and icon handling, but also the login process.  Not quite sure how to
  66 speed up that part without replacing NFS with for example NBD, and
  67 that is not really an option at the moment.</p>
  68
  69 <p>If you got feedback on this issue, please let us know on debian-edu
  70 (at) lists.debian.org.</p>
  71 </div>
  72
  73       <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>
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