C#だけど2マイクロ秒くらいだよ。
var sw = new System.Diagnostics.Stopwatch();
sw.Start();
for (var i = 0; i < 1000; i++) {new Thread(F);}
decimal time = (decimal)sw.ElapsedTicks / System.Diagnostics.Stopwatch.Frequency;
Console.WriteLine("{0} [ms]", time / 1000 * 1000);