Improving performance of multithreaded HttpWebRequests in .NET

Question

I am trying to measure the throughput of a webservice.

In order to do that, I have written a small tool that continuously sends requests and reads responses from a number of threads.

The contents of the inner loop of each thread looks like this:

public void PerformRequest() {   WebRequest webRequest = WebRequest.Create(_uri);    webRequest.ContentType = "application/ocsp-request";   webRequest.Method = "POST";   webRequest.Credentials = _credentials;   webRequest.ContentLength = _request.Length;   ((HttpWebRequest)webRequest).KeepAlive = false;    using (Stream st = webRequest.GetRequestStream())     st.Write(_request, 0, _request.Length);    using (HttpWebResponse httpWebResponse = (HttpWebResponse)webRequest.GetResponse())   using (Stream responseStream = httpWebResponse.GetResponseStream())   using (BufferedStream bufferedStream = new BufferedStream(responseStream))   using (BinaryReader reader = new BinaryReader(bufferedStream))   {     if (httpWebResponse.StatusCode != HttpStatusCode.OK)       throw new WebException("Got response status code: " + httpWebResponse.StatusCode);      byte[] response = reader.ReadBytes((int)httpWebResponse.ContentLength);     httpWebResponse.Close();   }       } 

It seems to work okay, except that something seems to be limiting the tool. If I run two instances of the tool with each 40 threads, I get significantly more throughput than one instance with 80 threads.

I found the ServicePointManager.DefaultConnectionLimit property, which I set to 10000 (and it makes no difference if I set it through app.config as suggested by Jader Dias).

Are there any other settings in .NET or on my machine that can influence the performance? (I am running Vista, but I see the same problem on Windows Server 2003).

Perhaps some restrictions on how many connections a single process can make?

Answer 1

You must set the maxconnection parameter at the app.config or web.config file:

<?xml version="1.0" encoding="utf-8" ?> <configuration>   <system.net>     <connectionManagement>       <add address="*" maxconnection="80"/>     </connectionManagement>   </system.net> </configuration> 

Values up to 100 work very well with Windows XP.

Update: I just found out that the method above is an alternative way to set the System.Net.ServicePointManager.DefaultConnectionLimit