Performance of Object.GetType()

Question

We have lots of logging calls in our app. Our logger takes a System.Type parameter so it can show which component created the call. Sometimes, when we can be bothered, we

Answer 1

I strongly suspect that GetType() will take significantly less time than any actual logging. Of course, there's the possibility that your call to Logger.Log won't do any actual IO... I still suspect the difference will be irrelevant though.

EDIT: Benchmark code is at the bottom. Results:

typeof(Test): 2756ms
TestType (field): 1175ms
test.GetType(): 3734ms

That's calling the method 100 million times - the optimisation gains a couple of seconds or so. I suspect the real logging method will have a lot more work to do, and calling that 100 million times will take a lot longer than 4 seconds in total, even if it doesn't write anything out. (I could be wrong, of course - you'd have to try that yourself.)

In other words, as normal, I'd go with the most readable code rather than micro-optimising.

using System;
using System.Diagnostics;
using System.Runtime.CompilerServices;

class Test
{
    const int Iterations = 100000000;

    private static readonly Type TestType = typeof(Test);

    static void Main()
    {
        int total = 0;
        // Make sure it's JIT-compiled
        Log(typeof(Test)); 

        Stopwatch sw = Stopwatch.StartNew();
        for (int i = 0; i < Iterations; i++)
        {
            total += Log(typeof(Test));
        }
        sw.Stop();
        Console.WriteLine("typeof(Test): {0}ms", sw.ElapsedMilliseconds);

        sw = Stopwatch.StartNew();
        for (int i = 0; i < Iterations; i++)
        {
            total += Log(TestType);
        }
        sw.Stop();
        Console.WriteLine("TestType (field): {0}ms", sw.ElapsedMilliseconds);

        Test test = new Test();
        sw = Stopwatch.StartNew();
        for (int i = 0; i < Iterations; i++)
        {
            total += Log(test.GetType());
        }
        sw.Stop();
        Console.WriteLine("test.GetType(): {0}ms", sw.ElapsedMilliseconds);
    }

    // I suspect your real Log method won't be inlined,
    // so let's mimic that here
    [MethodImpl(MethodImplOptions.NoInlining)]
    static int Log(Type type)
    {
        return 1;
    }
}