an ASP.NET performance bottleneck mystery

Question

A classic ASP.NET app - AppSrv + MS SQL DB. Both servers are heavy-lifters 8 cores, 20 GB of RAM. When load testing, the throughput goes somewhere to 400 VirtualUsers (according

Answer 1

Problem is probably in your machine.config file.

You should check following configuration parameters:

• maxconnection
• maxIoThreads
• maxWorkerThreads
• minFreeThreads
• minLocalRequestFreeThreads

For short description check: IIS 6.0 Tuning for Performance

There are some differences between ASP.NET 1.1 and ASP.NET 2.0

ASP.NET 1.1

Guidelines about some practical values you can find in:

• Microsoft Kb article 821268
• MSDN Article "Chapter 6 — Improving ASP.NET Performance - Threading Explained"

Default values are way to low for any practical use and should be corrected according to suggestions in linked articles.

ASP.NET 2.0

Parameters are moved to processModel section and parameters are auto configured. Besides auto configuration, you can manually set parameter values, so you should check if:

• processModel is enabled
• autoConfig is set to true
  or
• parameters are set to correct values

For detailed description check: ASP.Net 2.0 processModel