Program.log

// * Detailed results *
Program_GetSystemTimeAsFileTime
Mean = 15.0677 ns, StdError = 0.0775 ns (0.51%); N = 60, StdDev = 0.6000 ns
Min = 14.3962 ns, Q1 = 14.6196 ns, Median = 14.8500 ns, Q3 = 15.3732 ns, Max = 17.0593 ns
IQR = 0.7536 ns, LowerFence = 13.4891 ns, UpperFence = 16.5036 ns
ConfidenceInterval = [14.9159 ns; 15.2195 ns] (CI 95%)


Program_UtcNow
Mean = 5.0350 ns, StdError = 0.0096 ns (0.19%); N = 110, StdDev = 0.1007 ns
Min = 4.9268 ns, Q1 = 4.9695 ns, Median = 4.9905 ns, Q3 = 5.0597 ns, Max = 5.4673 ns
IQR = 0.0902 ns, LowerFence = 4.8343 ns, UpperFence = 5.1949 ns
ConfidenceInterval = [5.0162 ns; 5.0538 ns] (CI 95%)


Total time: 00:02:05 (125.07 sec)

// * Summary *

BenchmarkDotNet=v0.9.4.0
OS=Microsoft Windows NT 6.2.9200.0
Processor=Intel(R) Core(TM) i7-4800MQ CPU @ 2.70GHz, ProcessorCount=8
Frequency=2630623 ticks, Resolution=380.1381 ns, Timer=TSC
HostCLR=MS.NET 4.0.30319.42000, Arch=32-bit RELEASE
JitModules=clrjit-v4.6.1080.0

Type=Program  Mode=Throughput  

                  Method |     Median |    StdDev |
------------------------ |----------- |---------- |
 GetSystemTimeAsFileTime | 14.8500 ns | 0.6000 ns |
                  UtcNow |  4.9905 ns | 0.1007 ns |

// ***** BenchmarkRunner: End *****

UnsafePInvoke.cs

public class Program
{
    static void Main() => BenchmarkRunner.Run<Program>();

    [Benchmark]
    public DateTime UtcNow() => DateTime.UtcNow;

    [Benchmark]
    public unsafe long GetSystemTimeAsFileTime()
    {
        long fileTime;
        GetSystemTimeAsFileTime(&fileTime);

        return fileTime;
    }

    [DllImport("kernel32.dll")]
    public static extern unsafe void GetSystemTimeAsFileTime(long* systemTimeAsFileTime);

}