FSCacher.cs

using System.Collections.Concurrent;
using System.IO.MemoryMappedFiles;

using BlockingCollection<string> coll = new();

var threads = new Thread[100];
foreach (ref var thread in threads.AsSpan())
{
    thread = new Thread(RunThread) { IsBackground = true };
    thread.Start(coll);
}

var filesFromInputDirectories =
    from arg in args
    where Directory.Exists(arg)
    let dir = new DirectoryInfo(arg)
    from file in dir.EnumerateFiles("*", SearchOption.AllDirectories)
    select file;

var inputFiles =
    from arg in args
    where File.Exists(arg)
    select new FileInfo(arg);

var files =
    from file in filesFromInputDirectories.Concat(inputFiles)
    where file.Length > 0
    orderby file.Length
    select file;

foreach (var file in files.Distinct())
{
    coll.Add(file.FullName);
}

coll.CompleteAdding();

foreach (var thread in threads)
{
    thread.Join();
}

static unsafe void RunThread(object? collObj)
{
    if (collObj is not BlockingCollection<string> coll)
    {
        throw new ArgumentException("Expected a collection.", nameof(collObj));
    }

    foreach (string fl in coll.GetConsumingEnumerable())
    {
        using var fs = new FileStream(fl, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete);
        using var f = MemoryMappedFile.CreateFromFile(fs, null, 0, MemoryMappedFileAccess.Read, HandleInheritability.None, true);
        using var acc = f.CreateViewAccessor(0, 0, MemoryMappedFileAccess.Read);
        long len = acc.Capacity;
        byte* b = null;
        try
        {
            acc.SafeMemoryMappedViewHandle.AcquirePointer(ref b);
            for (long i = 0; i < len; i += 4096)
            {
                _ = b[i];
            }
        }
        catch (Exception ex)
        {
            Console.Error.WriteLine(ex);
        }
        finally
        {
            if (b != null)
            {
                acc.SafeMemoryMappedViewHandle.ReleasePointer();
            }
        }
    }
}