High memory usage by ASP.NET applications

Question

We have an issue with some of our ASP.Net applications. Some of our apps claim a large amount of memory from start as their working set.

On our 2 webfarm-servers (4g

Answer 1

Removing all Telerik Kendo MVC references (dll and such) fixed our problems. If we run the application without, all our memory problems are gone and we see normal memory use.

Basically: it was an external library causing high memory use.

Answer 2

I had a similar problem with some of my applications. I was able to solve the problem by properly closing the disposable database resources by wrapping them in using clauses.

For Entity Framework, that would mean to ensure you always close your context after each request. Connections should be disposed between requests.

using (var db = new MyEFContext())
{
   // Execute queries here
   var query = from u as db.User
               where u.UserId = 1234
               select u.Name;

   // Execute the query.
   return query.ToList();

   // This bracket will dispose the context properly.
}

You may need to wrap the context into a service that request-caches your context in order to keep it alive throughout the request, and disposes of it when complete.

Or, if using the pattern of having a single context for the entire controller like in the MSDN examples, make sure you override the Dispose(bool) method, like the example here.

protected override void Dispose(bool disposing)
{
    if (disposing)
    {
        db.Dispose();
    }
    base.Dispose(disposing);
}

So your controller (from above) should look like this:

namespace Foo.Api
{
    public class BarController : ApiController
    {
        private FooContext db = new FooContext(); 

        public IQueryable<Bar> GetBar(string bla)
        {
             return db.Bar.Where(f => f.Category.Equals(bla)).OrderBy(f => f.Year);
        }

        // WebApi 2 will call this automatically after each 
        // request. You need this to ensure your context is disposed
        // and the memory it is using is freed when your app does garbage 
        // collection.
        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                db.Dispose();
            }
            base.Dispose(disposing);
        }
    }
}

The behavior I saw was that the application would consume a lot of memory, but it could garbage collect enough memory to keep it from ever getting an OutOfMemoryException. This made it difficult to find the problem, but disposing the database resources solved it. One of the applications used to hover at around 600 MB of RAM usage, and now it hovers around 75 MB.

But this advice doesn't just apply to database connections. Any class that implements IDisposable should be suspect if you are running into memory leaks. But since you mentioned you are using EntityFramework, it is the most likely suspect.