C# メソッドをasyncにする、しないのパフォーマンス比較

asyncRead.cs

using System;
using System.IO;
using System.Linq;
using System.Threading.Tasks;

namespace ConsoleApplication4
{
    class Program
    {
        static void Main(string[] args)
        {
            Test().Wait();
            Console.Read();
        }

        static async Task Test()
        {
            var text = string.Join(Environment.NewLine, Enumerable.Range(1, 100000).Select(_ => Guid.NewGuid()));
            using (var reader = new TextReaderWrapper(new StringReader(text)))
            {
                while (null != await reader.ReadLineAsync()) ;
            }

            for (int i = 0; i < 10; i++)
            {
                var sw = System.Diagnostics.Stopwatch.StartNew();
                using (var reader = new TextReaderWrapper(new StringReader(text)))
                {
                    while (null != await reader.ReadLineAsync()) ;
                }
                sw.Stop();
                Console.Write(sw.ElapsedMilliseconds + ", ");

                sw.Restart();
                using (var reader = new TextReaderWrapper(new StringReader(text)))
                {
                    while (null != await reader.ReadLineAsync2()) ;
                }
                sw.Stop();
                Console.WriteLine(sw.ElapsedMilliseconds);
            }
        }

        class TextReaderWrapper : IDisposable
        {
            TextReader reader;
            public TextReaderWrapper(TextReader reader)
            {
                this.reader = reader;
            }
            
            public Task<string> ReadLineAsync()
            {
                return this.reader.ReadLineAsync();
            }

            public async Task<string> ReadLineAsync2()
            {
                return await this.reader.ReadLineAsync();
            }

            public void Dispose()
            {
                if (this.reader == null) return;
                this.reader.Dispose();
            }
        }
    }
}

result.txt

10万行のテキストをTextReader.ReadLineAsync() をラップしたメソッドで読み取り、実行時間を計測した結果

asyncなし, あり (単位 ms)
--------------
9, 20
8, 19
9, 19
9, 19
9, 19
8, 20
9, 19
8, 19
8, 19
9, 19
-------------
8.6, 19.2 (10回平均)

//asyncなし
public Task<string> ReadLineAsync()
{
    return this.reader.ReadLineAsync();
}

//asyncあり
public async Task<string> ReadLineAsync2()
{
    return await this.reader.ReadLineAsync();
}