GC.SuppressFinalize performance compared to non-finalizable object

Question

Is a finalizable object with GC.SuppressFinalize the same as a normal unfinalizable object? The code below seems to prove they're treated differently, both on .NET 2 and 4:

class Class1 {

    public Class1()
    {
        GC.SuppressFinalize(this);
    }

    //~Class1() { }
}

class Program
{
    static void Main(string[] args)
    {
        Stopwatch sw = new Stopwatch();
        sw.Start();

        for (int i=0; i<100000000; i++)
        {
            new Class1();
        }

        sw.Stop();
        Console.WriteLine(sw.ElapsedMilliseconds);
    }
}

Adding the finalizer, but not changing anything else, causes the code to take far far longer (12601 ms compared to 889 ms).

I thought SuppressFinalize set a bit in the object header making the GC treat the object the same as a non-finalizable object, but this does not seem to be the case. So what's going on? What is different between a non-finalizable object and a finalizable object with GC.SuppressFinalize called on it?

Answer 1

As I understand it the CLR has a queue of objects for which finalization has been registered. Implementing a finalizer will put objects of the type on the queue. So in the case where the constructor calls SuppressFinalize, I imagine that the object is actually put on the queue only to be removed immediately, which could explain the overhead.