Directory.EnumerateFiles perf

Benchmark.cs

using System.Runtime.InteropServices;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

BenchmarkRunner.Run<FindFirstFileBenchmark>();

[MemoryDiagnoser]
public partial class FindFirstFileBenchmark
{
    [Params(@"F:\src\roslyn")]
    public string BasePath { get; set; } = "";

    [Params(@"F:\src\roslyn\artifacts\bin\Microsoft.Build.Tasks.CodeAnalysis\Debug\net10.0\cs\")]
    public string SearchPath { get; set; } = "";

    // ───────────────────────────── Managed ─────────────────────────────

    [Benchmark(Baseline = true)]
    public bool DirectoryEnumerateFiles()
    {
        var searchPath = SearchPath;
        while (searchPath != BasePath && searchPath is { })
        {
            if (Directory.EnumerateFiles(searchPath, "*.docx").Any())
                return true;

            searchPath = Path.GetDirectoryName(searchPath);
        }
        return false;
    }

    // ──────────────────────────── Native ────────────────────────────

    [Benchmark]
    public unsafe bool FindFirstFileW()
    {
        var searchPath = SearchPath;
        while (searchPath != BasePath && searchPath is { })
        {
            if (find(searchPath))
                return true;

            searchPath = Path.GetDirectoryName(searchPath);
        }
        return false;

        bool find(string searchPath)
        {
            string searchPattern = Path.Combine(searchPath, "*.docx");

            WIN32_FIND_DATAW findData;
            var handle = NativeMethods.FindFirstFileW(searchPattern, &findData);

            if (handle == new nint(-1))
                return false;

            NativeMethods.FindClose(handle);
            return true;
        }
    }
}

// ═══════════════════════════════ P/Invoke ═══════════════════════════════

internal static partial class NativeMethods
{
    [LibraryImport("kernel32.dll", EntryPoint = "FindFirstFileW", StringMarshalling = StringMarshalling.Utf16)]
    internal static unsafe partial nint FindFirstFileW(string lpFileName, WIN32_FIND_DATAW* lpFindFileData);

    [LibraryImport("kernel32.dll", EntryPoint = "FindNextFileW", StringMarshalling = StringMarshalling.Utf16)]
    [return: MarshalAs(UnmanagedType.Bool)]
    internal static unsafe partial bool FindNextFileW(nint hFindFile, WIN32_FIND_DATAW* lpFindFileData);

    [LibraryImport("kernel32.dll", EntryPoint = "FindClose")]
    [return: MarshalAs(UnmanagedType.Bool)]
    internal static partial bool FindClose(nint hFindFile);
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
internal unsafe struct WIN32_FIND_DATAW
{
    public FileAttributes dwFileAttributes;
    public System.Runtime.InteropServices.ComTypes.FILETIME ftCreationTime;
    public System.Runtime.InteropServices.ComTypes.FILETIME ftLastAccessTime;
    public System.Runtime.InteropServices.ComTypes.FILETIME ftLastWriteTime;
    public uint nFileSizeHigh;
    public uint nFileSizeLow;
    public uint dwReserved0;
    public uint dwReserved1;
    public fixed char cFileName[260];
    public fixed char cAlternateFileName[14];
}

BenchMarkDotNetResults.txt

// * Summary *

BenchmarkDotNet v0.14.0, Windows 11 (10.0.26200.7840)
AMD Ryzen 9 3900X, 1 CPU, 24 logical and 12 physical cores
.NET SDK 10.0.103
  [Host]     : .NET 10.0.3 (10.0.326.7603), X64 RyuJIT AVX2
  DefaultJob : .NET 10.0.3 (10.0.326.7603), X64 RyuJIT AVX2


| Method                  | BasePath        | SearchPath              | Mean     | Error   | StdDev   | Ratio | RatioSD | Gen0   | Allocated | Alloc Ratio |
|------------------------ |---------------- |------------------------ |---------:|--------:|---------:|------:|--------:|-------:|----------:|------------:|
| DirectoryEnumerateFiles | F:\\src\\roslyn | F:\\sr(...)0\\cs\\ [80] | 227.7 us | 2.02 us |  1.89 us |  1.00 |    0.01 | 0.2441 |   3.38 KB |        1.00 |
| FindFirstFileW          | F:\\src\\roslyn | F:\\sr(...)0\\cs\\ [80] | 383.3 us | 7.60 us | 11.37 us |  1.68 |    0.05 |      - |   1.94 KB |        0.57 |

// * Legends *
  BasePath    : Value of the 'BasePath' parameter
  SearchPath  : Value of the 'SearchPath' parameter
  Mean        : Arithmetic mean of all measurements
  Error       : Half of 99.9% confidence interval
  StdDev      : Standard deviation of all measurements
  Ratio       : Mean of the ratio distribution ([Current]/[Baseline])
  RatioSD     : Standard deviation of the ratio distribution ([Current]/[Baseline])
  Gen0        : GC Generation 0 collects per 1000 operations
  Allocated   : Allocated memory per single operation (managed only, inclusive, 1KB = 1024B)
  Alloc Ratio : Allocated memory ratio distribution ([Current]/[Baseline])
  1 us        : 1 Microsecond (0.000001 sec)

// * Diagnostic Output - MemoryDiagnoser *


// ***** BenchmarkRunner: End *****
Run time: 00:00:56 (56.9 sec), executed benchmarks: 2

Global total time: 00:01:03 (63.12 sec), executed benchmarks: 2