TestTryStartNoGCRegion.cs

static void TestTryStartNoGCRegion(long sizeInBytes, bool preventGC, bool overAllocate = false)
{
    Console.WriteLine("Prevent GC: {0}, Over Allocate: {1}", preventGC, overAllocate);
    try
    {
        bool succeeded = false;

        if (preventGC)
        {
            succeeded = GC.TryStartNoGCRegion(sizeInBytes); //, disallowFullBlockingGC: true);
            Console.WriteLine("TryStartNoGCRegion: Size={0:N0} MB ({1:N0} K or {2:N0} bytes) {3}",
                              sizeInBytes / 1024.0 / 1024.0, sizeInBytes / 1024.0, sizeInBytes,
                              succeeded ? "SUCCEEDED" : "FAILED");
        }

        // TryStartNoGCRegion() causes a GC Collection, so call this once it's completed
        var gcBefore = new GCInfo();
        if (!preventGC || succeeded)
        {
            long allocated = 0;
            var numRuns = 5;
            var sizePerRun = sizeInBytes / numRuns;
            if (overAllocate)
                numRuns += 5;

            var lastGC = new GCInfo();
            for (int i = 0; i < numRuns; i++)
            {                    
                var test = new byte[sizePerRun];
                allocated += (test.Length);

                var currentGC = new GCInfo();
                var totalMemory = GC.GetTotalMemory(forceFullCollection: false);
                var gcOccured = (currentGC.Gen0 > lastGC.Gen0 || currentGC.Gen1 > lastGC.Gen1 || currentGC.Gen2 > lastGC.Gen2);
                Console.WriteLine("Allocated: {0,6:N2} MB, Mode: {1,12}, Gen0: {2}, Gen1: {3}, Gen2: {4}, {5}",
                                    allocated / 1024.0 / 1024.0,
                                    GCSettings.LatencyMode,
                                    currentGC.Gen0 - gcBefore.Gen0, 
                                    currentGC.Gen1 - gcBefore.Gen1, 
                                    currentGC.Gen2 - gcBefore.Gen2,
                                    gcOccured ? "**" : "");
                lastGC = currentGC;
            }
            if (GCSettings.LatencyMode == GCLatencyMode.NoGCRegion)
                GC.EndNoGCRegion();
        }
    }
    catch (ArgumentOutOfRangeException argEx)
    {
        // totalSize exceeds the ephemeral segment size.
        Console.WriteLine("{0:N0} MB ({1:N0} K or {2:N0} bytes) - {3}", 
                          sizeInBytes / 1024.0 / 1024.0, sizeInBytes / 1024.0, sizeInBytes, argEx.Message);
    }
    catch (Exception ex)
    {
        Console.WriteLine("{0:N0} MB ({1:N0} K or {2:N0} bytes) - {3} {4}", 
                          sizeInBytes / 1024.0 / 1024.0, sizeInBytes / 1024.0, sizeInBytes, ex.GetType().Name, ex.Message);
    }

    Console.WriteLine();
}