Does iis 7.5 set a physical memory limit so that the garbage collector works more aggressively?

Question

I am currently doing load testing of an asp.net 4.0 web application hosted on a server with a 64-bit version of 2008 (iis 7.5).

The purpose of load testing is to determine the maximum memory usage of a web application if each page is cached simultaneously.

To evaluate this, I set the page output cache to 900 seconds, then I request every public URL through the xenu slen connection. This effectively requests 20,000 pages.

To control memory usage, I use both the Windows Performance Monitor and the Redgate 7.0 memory profiler.

I missed the test twice, test 1 with a physical memory limit set to 0 by default, and test 2 with a physical memory limit set to 921600 (900 MB).

Here is what I noticed

• In both tests, the application pool is never recycled.
• In test 1, the use of workflow memory is increased to 1300 MB. (Above test memory limit 2)
• In test 2, memory usage increases to 720 MB.
• In test 2, memory usage increases to 720 MB.
• In test 1, unused memory allocated for .Net is increased to 700 mb
• In test 2, it grows to 150 MB.

This leads me to my question: Does the physical memory limit set in iis 7.5 so that the garbage collector works more aggressively?

If it is not, what do I testify?

Answer 1

To really find if garbage collection is running, you can look at perf counters on it.

At a minimum, I would look at the Gen 0 counter and compare two scenarios.

http://msdn.microsoft.com/en-us/library/x2tyfybc.aspx