title: Unoconv/libreoffice command line convert very slow
body: <p>I'm using unoconv or libreoffice to convert documents, <code>odt-&gt;pdf</code>, by <code>PHP exec()</code>. This process is very fast on one of my server (about 1s).
  Now I have another, much faster server, and this process is taking almost 20s! 
  And it's with the same, small 20k files. I googled, I set the same configuration, and can't find any clues - what could be the reason?</p>
  
  <p>Result is the same when i'm using unoconv, and libreoffice directly. When <code>starting unoconv --listener</code> first, first conversion can be made in about 20 seconds. Then all conversions are fast again.</p>
  
  <p>It seems that simple starting Libreoffice is taking a lot of time, but why?</p>