ASP.NET "Sessions Timed Out" Counter (perfmon.exe)

Question

I'm currently load testing an ASP.NET application. I'm charging with 500 users on the app, and while it's running I'm checking, in a perfmon.exe console, the "Sessions Actives" and "Sessions Timed Out" counters on the web server.

In my web.config, the session timeout is 3 minutes (for test's purpose).

So as the test goes, the "Sessions Actives" counter stays on about 900 active sessions, which I assume is normal because of the 500 active users and about 400 other whose sessions haven't timed out yet.

But when I look at the "Session Timed Out" counter, it countinuously increases. It just goes down gradually when the load test finishes.

What is this counter exactly? As I understand it, it's the deprecated sessions that have not been yet cleaned up (by the garbage collector?) and are still using memory.

Since our application is using a huge ammount of memory, I'm trying to find exactly where is that memory.

Answer 1

The counter seems to be indicating what is happening. i.e. As the sessions that are active start up, the counter for active goes to the right number.. and at some point they start to die down and they trigger the session time out to increase (i.e. the sessions that are summarily dismissed by the ASP.NET infrastructure). I am not sure what you are expecting to see. I recommend reading the chapters, 15, 16 and 17 of the Improving .NET Application Performance and Scalability book. They are pretty enlightening in this regard.