.NET 8 - String concat with + and StringBuilder with PGO on v PGO off

StringConcatDPGO.cs

using System.Text;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Columns;
using BenchmarkDotNet.Configs;
using BenchmarkDotNet.Environments;
using BenchmarkDotNet.Jobs;
using BenchmarkDotNet.Reports;

namespace BenchmarkDotNet.Samples
{
    [Config(typeof(Config))]
    [HideColumns(Column.RatioSD, Column.AllocRatio, Column.Error, Column.StdDev, Column.Runtime)]
    public class StringConcatDPGO
    {
        [Params(1000)]
        public int Concats { get; set; }

        [Benchmark]
        public string Plus()
        {
            var result = string.Empty;
            for (int i = 0; i < Concats; i++)
            {
                result = result + "1234567890";
            }

            return result;
        }

        [Benchmark]
        public string SB_10()
        {
            StringBuilder result = new StringBuilder();
            for (int i = 0; i < Concats; i++)
            {
                result.Append("1234567890");
            }

            return result.ToString();
        }

        private class Config : ManualConfig
        {
            public Config()
            {
                AddJob(Job.Default.WithId("Non DPGO")
                    .WithBaseline(true)
                    .WithRuntime(CoreRuntime.Core80)
                    .WithEnvironmentVariables(
                        new EnvironmentVariable("DOTNET_TieredPGO", "0")));

                AddJob(Job.Default.WithId("DPGO")
                    .WithRuntime(CoreRuntime.Core80)
                    .WithEnvironmentVariables(
                        new EnvironmentVariable("DOTNET_TieredPGO", "1")));

                SummaryStyle =
                    SummaryStyle.Default.WithRatioStyle(RatioStyle.Percentage)
                    .WithTimeUnit(Perfolizer.Horology.TimeUnit.Millisecond);
            }
        }
    }
}