Reduce overheads of EventSource.WriteEvent(int, object[]) with ETW

[stephentoub]

Cuts allocation by ~3-4x on basic use cases by avoiding a List<int>(8) and List<object>(8) allocation along with the underlying arrays.

cc: @josalem, @brianrob

Method	Toolchain	Mean	Error	StdDev	Ratio	Allocated
Log	\main\corerun.exe	336.3 ns	2.58 ns	2.29 ns	1.00	296 B
Log	\pr\corerun.exe	311.2 ns	4.82 ns	4.27 ns	0.93	88 B

using BasicEventSourceTests;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System.Diagnostics.Tracing;

[MemoryDiagnoser]
public class Program
{
    static void Main(string[] args) => BenchmarkSwitcher.FromAssemblies(new[] { typeof(Program).Assembly }).Run(args);

    private static EtwListener s_listener;

    [GlobalSetup]
    public void Setup()
    {
        s_listener = new EtwListener(null);
        s_listener.EventSourceSynchronousEnable(MyEventSource.Log);
    }

    [GlobalCleanup]
    public void Cleanup() => s_listener.Dispose();

    [Benchmark]
    public void Log() => MyEventSource.Log.SomethingCool(42, 84);
}

[EventSource]
class MyEventSource : EventSource
{
    internal static readonly MyEventSource Log = new MyEventSource();

    [Event(1, Level = EventLevel.LogAlways)]
    public void SomethingCool(int i, float j) => WriteEvent(1, i, j);
}

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Issue Details

---

Cuts allocation by ~3-4x on basic use cases by avoiding a List<int>(8) and List<object>(8) allocation along with the underlying arrays.

cc: @josalem, @brianrob

Method	Toolchain	Mean	Error	StdDev	Ratio	Allocated
Log	\main\corerun.exe	336.3 ns	2.58 ns	2.29 ns	1.00	296 B
Log	\pr\corerun.exe	311.2 ns	4.82 ns	4.27 ns	0.93	88 B

using BasicEventSourceTests;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System.Diagnostics.Tracing;

[MemoryDiagnoser]
public class Program
{
    static void Main(string[] args) => BenchmarkSwitcher.FromAssemblies(new[] { typeof(Program).Assembly }).Run(args);

    private static EtwListener s_listener;

    [GlobalSetup]
    public void Setup()
    {
        s_listener = new EtwListener(null);
        s_listener.EventSourceSynchronousEnable(MyEventSource.Log);
    }

    [GlobalCleanup]
    public void Cleanup() => s_listener.Dispose();

    [Benchmark]
    public void Log() => MyEventSource.Log.SomethingCool(42, 84);
}

[EventSource]
class MyEventSource : EventSource
{
    internal static readonly MyEventSource Log = new MyEventSource();

    [Event(1, Level = EventLevel.LogAlways)]
    public void SomethingCool(int i, float j) => WriteEvent(1, i, j);
}

Author:	stephentoub
Assignees:	-
Labels:	area-System.Diagnostics.Tracing, tenet-performance
Milestone:	6.0.0

[brianrob]

LGTM, but will defer to @josalem for final sign-off. It would also be good to run the EventSource tests elevated (locally is fine), to confirm that the expected payloads come all the way through. Historically, the CI doesn't run elevated, and so the ETW tests don't run - only the EventListener tests run.

Also, I suspect that you might need to #ifdef this (grr...) due to the fact that this code targets .NET Framework via the EventSource.Redist package. That might be where the CI error is coming from too.

[stephentoub]

It would also be good to run the EventSource tests elevated (locally is fine)

you might need to #ifdef this (grr...)

Grrr indeed. I'm looking forward to us archiving that project ;-) I pushed a commit to address it.

[josalem]

LGTM! Thanks for running the tests elevated 😃.

It looks like the CI failures are NuGet restore failures. Let me see about rerunning the innerloop legs.

[josalem]

azp run runtime-dev-innerloop

[josalem]

Whoops, looks like GH posted that as a comment rather than a PR review.