EventSource startup initialization

[noahfalk]

Fixes #105845

Previously MetricsEventSource wasn't being created for apps that didn't ever create a Meter. This caused a chicken-and-egg problem for RuntimeMetrics which weren't created until MetricsEventSource started a tracing session. This change ensures that MetricsEventSource will be created on demand if ETW, EventPipe, or EventListener based tooling starts a tracing session. I took some extra effort to create the EventSource in a deferred fashion to avoid eager loading System.Diagnostics.DiagnosticSource.dll when it might never be needed.

Aside from the fix there were some small improvements:

• Moved NativeRuntimeEventSource to initialize in the same place as other startup EventSources
• Removed a useless lock(EventListener.EventListenersLock) around EventPipe eventProvider registration

[noahfalk]

I think this is ready for review now. The CI failures appear spurious.
@tarekgh @brianrob @dotnet/dotnet-diag @lambdageek @lateralusX

[noahfalk]

@LakshanF @MichalStrehovsky - this change also adjusted the NativeAOT startup slightly by moving the ModuleInitializer attribute from RuntimeEventSource.Initialize() to EventSource.InitializeDefaultEventSources().

@elinor-fung - this change adjusts the startup path you were just editing earlier this week.

[tarekgh]

LGTM. Thanks!

[brianrob]

I suspect that I just missed something here, but want to check - I see where you register the listeners for ETW and EventPipe and trigger creation if/when a command comes in. How is EventListener handled? Something will need to create the MetricsEventSource so that OnEventSourceCreated gets called. I'm assuming you have this covered and I just missed it.

[noahfalk]

How is EventListener handled? Something will need to create the MetricsEventSource so that OnEventSourceCreated gets called. I'm assuming you have this covered and I just missed it.

Yep, thats this part right here to handle EventListener callbacks:
https://github.com/dotnet/runtime/pull/106014/files#diff-ebcaac338c0ea28059b6d78c1d8725941f461bb7d6b08d83024c3f873ce012a1R4579-R4581

[MichalStrehovsky]

@LakshanF @MichalStrehovsky - this change also adjusted the NativeAOT startup slightly by moving the ModuleInitializer attribute from RuntimeEventSource.Initialize() to EventSource.InitializeDefaultEventSources().

This means any app with EventSourceSupport=true will pay for this in terms of size, but it doesn't look terrible. I triggered a rt-sz run and it seems like we'll have a 30 kB regression in dotnet new webapiaot: MichalStrehovsky/rt-sz#60 (comment). Most of this cost actually comes from Type.GetType since nothing else uses that API.

It doesn't make a huge difference in EventSource cost (dotnet new webapiaot followed by dotnet publish vs dotnet publish -p:EventSourceSupport=false shows EventSourceSupport increases size by 11%, or 1 MB).

[brianrob]

How is EventListener handled? Something will need to create the MetricsEventSource so that OnEventSourceCreated gets called. I'm assuming you have this covered and I just missed it.

Yep, thats this part right here to handle EventListener callbacks: https://github.com/dotnet/runtime/pull/106014/files#diff-ebcaac338c0ea28059b6d78c1d8725941f461bb7d6b08d83024c3f873ce012a1R4579-R4581

Thanks! LGTM.

[noahfalk]

Thanks for the feedback, it should all be addressed now. Once CI confirms no new issues I'll merge.