[Benchmark]
public int Rented()
{
    var array = _pool.Rent(2);
    array[0] = 1;
    array[1] = 2;
    var result = array[0] + array[1];
    _pool.Return(array);
    return result;
}

[Benchmark(Baseline = true)]
public int Allocated()
{
    var array = new int[2];
    array[0] = 1;
    array[1] = 2;

    var result = array[0] + array[1];
    return result;
}

BenchmarkDotNet=v0.11.5, OS=Windows 10.0.17763.475 (1809/October2018Update/Redstone5)
AMD Ryzen 7 2700X, 1 CPU, 8 logical and 4 physical cores
.NET Core SDK=3.0.100-preview5-011568
  [Host]     : .NET Core 3.0.0-preview5-27626-15 (CoreCLR 4.6.27622.75, CoreFX 4.700.19.22408), 64bit RyuJIT
  DefaultJob : .NET Core 3.0.0-preview5-27626-15 (CoreCLR 4.6.27622.75, CoreFX 4.700.19.22408), 64bit RyuJIT


|    Method |      Mean |     Error |    StdDev | Ratio | RatioSD |  Gen 0 | Gen 1 | Gen 2 | Allocated |
|---------- |----------:|----------:|----------:|------:|--------:|-------:|------:|------:|----------:|
|    Rented | 29.563 ns | 0.1736 ns | 0.1450 ns |  5.01 |    0.27 |      - |     - |     - |         - |
| Allocated |  5.825 ns | 0.1440 ns | 0.2522 ns |  1.00 |    0.00 | 0.0077 |     - |     - |      32 B |