title: Increase Max Connections under Ubuntu? (Tsung concurrency test)
body: <p>I am testing NodeJs, especially the concurrency. I am using Tsung for this. 
  Unfortunately Tsung seems not be able to spawn enough users. I'm only getting about 30K simultaneous connections although ~2GB RAM is still unused. (<a href="http://img715.imageshack.us/img715/2428/screenshotocy.png" rel="nofollow noreferrer">Check the charts</a>)</p>
  
  <p>The XML-Config File is the following: </p>
  
  <pre><code>&lt;tsung loglevel="notice" version="1.0"&gt;
  &lt;!-- Client side setup --&gt;
  −
  &lt;clients&gt;
  &lt;client host="localhost" use_controller_vm="false"/&gt;
  &lt;client host="localhost" use_controller_vm="false"/&gt;
  &lt;/clients&gt;
  &lt;!-- Server side setup --&gt;
  −
  &lt;servers&gt;
  &lt;server host="localhost" port="8000" type="tcp"/&gt;
  &lt;/servers&gt;
  −
  &lt;!--
   to start os monitoring (cpu, network, memory). Use an erlang
    agent on the remote machine or SNMP. erlang is the default 
  --&gt;
  −
  &lt;monitoring&gt;
  &lt;monitor host="localhost" type="erlang"/&gt;
  &lt;/monitoring&gt;
  −
  &lt;load&gt;
  −    
  &lt;arrivalphase phase="1" duration="50" unit="minute"&gt;
  &lt;users interarrival="0.000000001" unit="second"/&gt;
  &lt;/arrivalphase&gt;
  &lt;/load&gt;
  −
  &lt;sessions&gt;
  −
  &lt;session name="nodeJS" probability="100" type="ts_http"&gt;
  −
  &lt;for from="0" to="40" incr="1" var="counter"&gt;
  −
  &lt;request&gt;
  &lt;http url="http://localhost:8000/" version="1.1" method="GET"/&gt;
  &lt;/request&gt;
  &lt;thinktime random="false" value="300"/&gt;
  &lt;/for&gt;
  &lt;/session&gt;
  &lt;/sessions&gt;
  &lt;/tsung&gt;
  </code></pre>
  
  <p>So how to increase the users, so that all the RAM is used???</p>