GCSamples.cs

using System;
using System.Globalization;
using System.Runtime;
using System.Threading;

namespace ConsoleApplication1
{
    internal class Program
    {
        // IMPORTANT: run release x64 build without debugging (Ctrl-F5 to launch)
        // IMPORTANT: add the following lines into app.config to enable the server GC:
        /*
          <runtime>
            <gcServer enabled="true"/>
          </runtime>
         */
        private static void Main()
        {
            Console.WindowWidth = 120;

            int SingleAllocSize = 64 * 1024; // lower than LOH treshold
            int RepeatCount = 8 * 1024;      // +512 mb at each step
            Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture; // to ignore locale on console output.

            Console.WriteLine("GC batch:");
            GCSettings.LatencyMode = GCLatencyMode.Batch;
            for (int i = 1; i <= 10; i++)
            {
                AllocMem(SingleAllocSize, i * RepeatCount);
            }

            Console.WriteLine();
            Console.WriteLine("GC low latency:");
            GCSettings.LatencyMode = GCLatencyMode.LowLatency;
            for (int i = 1; i <= 10; i++)
            {
                AllocMem(SingleAllocSize, i * RepeatCount);
            }

            Console.WriteLine("Done");
            Console.ReadKey();
        }

        private static void AllocMem(int allocSize, int allocCount)
        {
            var data = new byte[allocCount][];

            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();

            var mem = GC.GetTotalMemory(true);
            var gc00 = GC.CollectionCount(0);
            var gc01 = GC.CollectionCount(1);
            var gc02 = GC.CollectionCount(2);

            for (int i = 0; i < data.Length; i++)
            {
                data[i] = new byte[allocSize];
            }

            long[] genMem = new long[3];
            foreach (var item in data)
            {
                genMem[GC.GetGeneration(item)] += item.Length;
            }

            var mem2 = GC.GetTotalMemory(false);
            var gc10 = GC.CollectionCount(0);
            var gc11 = GC.CollectionCount(1);
            var gc12 = GC.CollectionCount(2);
            GC.KeepAlive(data);

            var m0 = genMem[0] / 1024d / 1024;
            var m1 = genMem[1] / 1024d / 1024;
            var m2 = genMem[2] / 1024d / 1024;
            var mTotal = (mem2 - mem) / 1024d / 1024;
            var gcDelta0 = gc10 - gc00;
            var gcDelta1 = gc11 - gc01;
            var gcDelta2 = gc12 - gc02;

            Console.WriteLine(
                "Allocated, MB: {0,8:N2} \t GC gen 0|1|2, MB: {1,8:N2} | {2,8:N2} | {3,8:N2} \t GC count 0-1-2: {4}-{5}-{6}",
                 mTotal, m0, m1, m2, gcDelta0, gcDelta1, gcDelta2);
        }
    }
}