COMException when using hardware counters and in-process toolchain

[mlessmann]

A COMException gets thrown when using the new in-process toolchain and hardware counters (any) on a class containing at least two benchmark methods.

Minimal repro (run as admin):

class Program
{
    static void Main(string[] args)
    {
        var config = DefaultConfig.Instance
            .With(Job.Default
                .With(InProcessToolchain.Instance)
                .WithHardwareCounters(HardwareCounter.TotalCycles));
        BenchmarkRunner.Run<Bench>(config);
    }
}

public class Bench
{
    [Benchmark]
    public void M1() { }

    [Benchmark]
    public void M2() { }
}

The following exception gets thrown during AfterSetup of the second method:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.Runtime.InteropServices.COMException: The WMI data block or event notification has already been enabled. (Exception from HRESULT: 0x8007106E)
   at System.Runtime.InteropServices.Marshal.ThrowExceptionForHRInternal(Int32 errorCode, IntPtr errorInfo)
   at Microsoft.Diagnostics.Tracing.Session.TraceEventProfileSources.Set(Int32[] profileSourceIDs, Int32[] profileSourceIntervals)
   at BenchmarkDotNet.Diagnostics.Windows.PmcDiagnoser.GetInitializedStats(Benchmark benchmark)
   at BenchmarkDotNet.Diagnostics.Windows.EtwDiagnoser`1.Start(Process process, Benchmark benchmark)
   at BenchmarkDotNet.Diagnostics.Windows.PmcDiagnoser.BeforeMainRun(Process process, Benchmark benchmark)
   at BenchmarkDotNet.Diagnosers.CompositeDiagnoser.<>c__DisplayClass5_0.<BeforeMainRun>b__0(IDiagnoser diagnoser)
   at BenchmarkDotNet.Extensions.CommonExtensions.ForEach[T](IList`1 source, Action`1 command)
   at BenchmarkDotNet.Diagnosers.CompositeDiagnoser.BeforeMainRun(Process process, Benchmark benchmark)
   at BenchmarkDotNet.Toolchains.InProcess.InProcessHost.SendSignal(HostSignal hostSignal)
   at BenchmarkDotNet.Engines.Engine.Run()
   at BenchmarkDotNet.Toolchains.InProcess.InProcessRunner.Runnable.RunCore(IHost host, Benchmark benchmark, BenchmarkActionCodegen codegenMode)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at BenchmarkDotNet.Toolchains.InProcess.InProcessRunner.Run(IHost host, Benchmark benchmark, BenchmarkActionCodegen codegenMode)

I'm using the current nightly build 0.10.3.39 running on .NET 4.6 in VS2015 on Windows 10.

[adamsitnik]

Hello @mlessmann

I am glad that you try our new features. I am afraid that it's impossible to combine these two features. When we run in process we do some extra work, that can spoil the results of the Hardware Counters. That's why for the non-in process toolchain we perform separate run for the diagnosers only. I will find some free time and provide the docs and nice warning about this limitation