title: Does setting the physical memory limit in iis 7.5 cause the garbage collector to operate more aggressively?
body: <p>I am currently undertaking load testing of a  asp.net 4.0 web application hosted on a 64bit 2008 server (iis 7.5).  </p>
  
  <p>The purpose of the load testing it to determine the maximum memory usage by the web application if every page is cached simultaneously. </p>
  
  <p>To evaluate this I set the output cache duration of the pages to 900 seconds then I request each publicly accessible url via xenu link sluth. This effectively request 20,000 or so pages. </p>
  
  <p>To monitor memory usage I am using both Windows performance monitor and Redgate memory profiler 7.0.</p>
  
  <p>I have run the test twice, test 1 with the physical memory limit set to the default 0, and test 2 with the physical memory limit set to 921600 (900mb).</p>
  
  <p>Here is what I have observed, </p>
  
  <ul>
  <li>In both tests the application pool is never recycled. </li>
  <li>In test 1,  the worker process memory usage grows to 1,300mb. (Above the memory limit of test 2)</li>
  <li>In test 2, memory usage grows to 720mb. </li>
  <li>In test 2, memory usage grows to 720mb. </li>
  <li>In test 1, the unused memory allocated to .Net grows to 700mb </li>
  <li>In test 2 it  grows to 150mb.</li>
  </ul>
  
  <p>This leads me to my question, does setting the physical memory limit in iis 7.5 cause the garbage collector to operate more aggressively?</p>
  
  <p>If this is not the case what am I witnessing?</p>