title: a large number of apache threads when I do the Apache concurrent test in perfork MPM
body: <p>My Apache is 2.4.18 in Ubuntu 16.04.</p>
  
  <p>When I do the concurrent test in Jmeter, my test script is like this:
  <a href="https://i.stack.imgur.com/VuXkq.png" rel="nofollow noreferrer">Test Script in the concurrent testing</a></p>
  
  <p>I use <code>sar -q 1</code> and <code>htop</code> to monitor the number of processes and threads</p>
  
  <p>when it's 5 users concurrent, the the number of processes and threads growth very fast(260 --> 1417 in four minutes)</p>
  
  <p>and I also get the result in <code>pidstat -wt 1</code><a href="https://i.stack.imgur.com/IzSlC.png" rel="nofollow noreferrer">Monitor result</a></p>
  
  <p>What's wrong about my apache server? </p>
  
  <p>For my apache server , I use the prefork MPM(use processes).  Why there is so many apache threads?</p>
  
  <p>I try to modify the configuration(cat back the <code>Time out</code>/<code>KeepAliveTimeout</code>)and <code>mpm_prefork.conf</code>, but these don't work to me?</p>
  
  <p>I have no idea about finding the key to the problem. To the first, what should I do?
  Really thanks in advance.</p>