public interface ISomeInterface
        {
            int Do(int i);
        }

        // ...

        public struct SomeStruct : ISomeInterface
        {
            public int Do(int i) => i + 1;
        }
        public struct SomeStruct2 : ISomeInterface
        {
            public int Do(int i) => i - 1;
        }

        // ...

        private static int DoCore(this ISomeInterface x, int i) => x.Do(i);

        public static void Main(string[] args)
        {
            Console.WindowWidth = 120;

            const int Count = 100 * 1000 * 1000;
            SomeStruct s = new SomeStruct();

            Measure("DirectCall", () =>
            {
                for (int i = 0; i < Count; i++)
                {
                    s.Do(i);
                }
                return Count;
            });

            Measure("ExtensionMethod", () =>
            {
                for (int i = 0; i < Count; i++)
                {
                    s.DoCore(i);
                }
                return Count;
            });

            Console.WriteLine();
            Console.WriteLine("Done.");
            Console.ReadKey();
        }

        private static void Measure(string name, Func<long> callback)
        {
            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();

            var mem = GC.GetTotalMemory(true);
            var gc00 = GC.CollectionCount(0);
            var gc01 = GC.CollectionCount(1);
            var gc02 = GC.CollectionCount(2);

            var sw = Stopwatch.StartNew();
            var result = callback();
            sw.Stop();

            var mem2 = GC.GetTotalMemory(false);
            var gc10 = GC.CollectionCount(0);
            var gc11 = GC.CollectionCount(1);
            var gc12 = GC.CollectionCount(2);

            var memDelta = (mem2 - mem) / 1024.0;
            var gcDelta0 = gc10 - gc00;
            var gcDelta1 = gc11 - gc01;
            var gcDelta2 = gc12 - gc02;

            Console.WriteLine(
                "{0,20}: {1,5}ms, ips: {2,22:N} | Mem: {3,9:N2} kb, GC 0/1/2: {4}/{5}/{6} => {7,6}",
                name, sw.ElapsedMilliseconds, result / sw.Elapsed.TotalSeconds, memDelta, gcDelta0, gcDelta1, gcDelta2, result);
        }