Console.WriteLine speeds up my code?

Question

I have been looking into speeding up my application as it is performance critical... i.e. every millisecond I can get out of it is better. To do this I have a method that calls some other methods and each of these other methods is wrapped with a Stopwatch timer and Console.WriteLine calls. I.e.:

private void SomeMainMethod()
{
    System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
    sw.Start();
    SomeMethod();
    sw.Stop();
    Console.WriteLine("Time for SomeMethod = {0}ms", sw.ElapsedMilliseconds);

    sw.Reset();
    sw.Start();
    SomeOtherMethod();
    sw.Stop();
    Console.WriteLine("Time for SomeOtherMethod= {0}ms", sw.ElapsedMilliseconds);

    //...
}

The problem is whenever I comment out the Stopwatch and Console.WriteLine lines the code runs about 20ms (not 50) slower which is a lot for what I need.

Does anyone know why this is?

EDIT: The SomeMainMethod method and others in the class are also wrapped in a Stopwatch and Console.WriteLine calls similar to above.

The SomeMainMethod and the methods it calls is part of a class that is part of a Class Library that is called from a console testbed, all of which is single threaded.

For more information: The app is running in x86 .NET 4.6.1 Release mode with optimisations enabled. I am also running this in visual studio 2013 not outside of it.

Answer 1

After reading a very similar question with no answers I may have found the issue. In the comments section a user (ForguesR) made the following comment:

It is really a big guess : maybe because you are writing to IO your thread gets more processor time because WriteLine is synchronized and thus blocking other threads.

So I wanted to check if this was indeed the case so I changed SomeMainMethod to like the following:

NOTE: It is generally not advised to play around with thread priorities, this was only a workaround to test the theory. I would strongly advise against doing this in production code unless you are 100% sure you know what you are doing. Then probably still stay away from it.

private void SomeMainMethod()
{
    System.Threading.ThreadPriority tp = System.Threading.ThreadPriority.Normal;
    try
    {
        tp = System.Threading.Thread.CurrentThread.Priority;

        System.Threading.Thread.CurrentThread.Priority = System.Threading.ThreadPriority.Highest;

        System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
        sw.Start();
        SomeMethod();
        sw.Stop();
        Console.WriteLine("Time for SomeMethod = {0}ms", sw.ElapsedMilliseconds);

        sw.Reset();
        sw.Start();
        SomeOtherMethod();
        sw.Stop();
        Console.WriteLine("Time for SomeOtherMethod= {0}ms", sw.ElapsedMilliseconds);

        //...
    }
    finally
    {
        System.Threading.Thread.CurrentThread.Priority = tp;
    }
}

After making this change my code now runs consistently faster (~10ms) when the Console and Stopwatch lines are commented out. Therefore I believe his comment was probably correct, at least in my situation.