ASP.NET 4.0 PrivateBytesLimit not working

Does anybody know if there are any major changes in the output chache setting in the web.config in ASP.NET 4.0? I have created two websites one on .NET 3.5 and one on .NET 4.0. They have only one page with large html in it and output cache turn on. I made a small app to call the sites with different parameter value to increase the cached pages. In both web.config I added the following setting

<system.web>
    <caching>
        <cache privateBytesLimit="104857600" privateBytesPollTime="00:00:10"/>
    </caching>
</system.web>

Here are my page output cache settings:

<%@ OutputCache VaryByParam="d" Duration="50000"%>

which should limit the private bytes to 100 MB and should set the pooling interval to 10 seconds. I watched the memory growth of bot sites I noticed that every once in a while(about 10 seconds as I have set it in the web.config) the .NET 3.5 website's memory goes down.

The .NET 4.0 website's memory size first reaches 3 GB and then falls down to about 1.3 GB but not to it's limit of 100MB. The .NET 3.5 website's memory decreases to approximately 100 MB.

So my question is what am I doing wrong? What do I have to do to make my site free some cache when it reaches its private bytes limit. Are there any other settings I should do to 开发者_开发百科make this work.

Any help you could give me would be Greatly appreciated!