Add ETW events that would measure application start up time.

[Tanya-Solyanik]

This is a request from the runtime team, aligned with their Arm64 effort. Related to dotnet/runtime#64993

As an example, here’s a pointer to how the perf lab does this. All of the start-up tests emit an event when they have completed start-up: https://github.com/dotnet/performance/blob/23b05253055e3c5253bf4a1c8d4d767f33c2b77b/src/tools/ScenarioMeasurement/Startup/GenericStartupParser.cs#L8

[merriemcgaw]

Definitely something we want to try to measure.

[dreddy-work]

@Tanya-Solyanik, Are you planning to take this up in 7.0?

[Tanya-Solyanik]

@Tanya-Solyanik, Are you planning to take this up in 7.0?

No, this is a request from the runtime team. Someone from our team should work with Rich to understand his goal, and then we need to decide if his goals align with ours.

[elachlan]

This would be nice to have. One of my main goals for working on Winforms was to try and speed up app performance. We currently rely heavily on NGEN as a part of the install process(.net 4.8). Currently .NET 6 starts significantly slower.

Related runtime issue which has an example app: dotnet/runtime#13339

[JeremyKuhne]

Measuring time isn't really generically practical as there aren't great places to measure and we're at the mercy of Windows message processing. When I was working on startup performance I was seeing wildly fluctuating times on Application.Run for a new Form().

What we do need and should have are allocation tracking tests for startup scenarios. We can do a hacky bit where we implement some tests that expect a specific amount of thread allocations, but they'll need a lot of attention as changes in the lower level runtime will also impact this from time to time. It would be best to get a perf test solution up and running but I don't see that we'll get that scheduled in the near future.

@elachlan if you can come up with measurement points that you think would be useful we can discuss.

[elachlan]

Thanks for the information, I guess the ETW events would help application developers profile their code better in production scenarios.

For myself, I am interested in general performance improvements across the board. Not just start-up performance.

[jkotas]

What we do need and should have are allocation tracking tests for startup scenarios.

Note that the common techniques for reducing allocations often regress startup performance. GC allocations are not a good proxy for startup performance. The best proxy for tracking startup performance of .NET apps is total number and code size of managed methods that are touched during startup.