MVC3 memory management - asp.net-mvc-3

Question

What is the best way to check memory usage in an ASP.NET MVC3 application?
I have been told by my hosting provider to recyle the IIS application pool every so often to improve the speed of the site. Is this what is 'recommended practice'? Surely I shouldn't need to restart my application every so often? I'd much rather find out if it is an issue with memory usage in my application and correct it. So any tips & best practices you use would be quite helpful too.
The application is based on ASP.NET MVC3, C# and EF Code First. Any guidance, links appreciated.
EDIT:
I found this page after I posted, which is quite useful. But I'd still like to hear any other views.
ASP.NET MVC and EF Code First Memory Usage
Thank you

Answer 1

I have a site that never recycles (until the machine is rebooted weekly)
Your application generally should keep performing fine. If it doesn't, there is some leak.
This can occur because
Cache never expires
Cache never expires
Session storage keeps growing and never times out
ObjectContexts are never disposed and kept in the session, etc
Objects that should be disposed aren't
Objects that are created via a dependency injection container aren't setup to release after each request, and thus potentially have internal collections that keep growing.
There are more causes - but these are a few main ones.
So the question really is 'there is no best practice - it depends on your app'
If you are worried about current sessions during a restart, keep in mind a restart can be quick and current requests are allowed to finish (sometimes) and forms authentication tokens will survive the restart, however sessions will not unless you configure an out of process state server.
If your memory usage keeps growing, then setup a restart schedule, otherwise do once a week or never - or setup once memory goes to XYZ then reset. ASP.NET will restart automatically once a certain threshold is reached as well based on what the hoster has setup on memoryLimit:
http://msdn.microsoft.com/en-us/library/7w2sway1.aspx

Answer 2

By default IIS recycles the application pool automatically at an interval (I think is 29 hours or so) but that is surely set by the host, no matter how little or how much memory you're the process is using. THe recycling trigger can be a time interval or when the process hits a certain memory usage limit. I'm sure any shared host has both of them set.
About memory usage, you can use the GC.GetTotalMemory method which will give you an approximate usage. Even when using Perfmon the readings aren't very accurate but it gives you an idea.
//global.asax.cs
void Application_EndRequest(object o,EventArgs a)
{
var ctype=Context.Response.Headers["Content-Type"];
if (ctype == null || !ctype.Contains("text/html")) return;
Context.Response.Write(string.format("<p>Memory usage: {0}</p>",GC.GetTotalMemory(false)));
}
Be aware that you'll see the usage increasing increasing until the GC kicks in and the usage will drop to a more 'realistic' value.
If you have the money I recommend a specialized tool such as the Memory profiler
Other things you can do to at least be ready if the application has memory or performance problems:
Proper layering of the application, means you can refactor the more inefficient parts without affecting the others.
The Repository pattern will be very helpful, because you can start using EF , find out that EF uses to much memory (like in the link you've found), but then you could switch the repository implementation to use PetaPoco or Dapper.net.
In general an OR\M is more of a heavy library, if the application doesn't need ORM features but just a quick way to work with a db, use from the beginning a mico-Orm like those mentioned above.
Always dispose objects implementing IDisposable.
When dealing with large db records, use pagination. It's good for both server resources usage and user experience
Apply the YAGNI (You Aint Gonna Need It) principle as much as possible, this somehow implies a bit of TDD :)