Missing StartupFlags in Runtime/Start event

[kkokosa]

/Runtime/Start event contains StartupFlags field, informing on various attributes provided to host. They were very useful, for example in PerfView analysis - showed in GCStats CLR Startup Flags view. It was a super convenient way to check GC mode, with the help of CONCURRENT_GC/SERVER_GC values. Especially when analysis of sessions recorded on external, not fully controlled environments (like customer support etc.). These flags are reported in .NET Framework apps, but are not used in .NET Core/.NET 5.

I wonder how we can return to informing about GC modes in the recorded session? Do we need a new dedicated "GC settings" event for that (taking the opportunity to add something more than GC mode)? I've created an issue on PerfView side too, but apparently, we need runtime support for that. Or maybe I'm missing something and we can get this info from a trace?

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[brianrob]

@noahfalk, @tommcdon

[tommcdon]

@sywhang @josalem

[josalem]

You're correct, it looks like the startupMode and startupFlags parameters are both unset when the event is fired. This event should be showing up in .net traces, but that field will be zero. I'll take a look at where we can get that information from and if we can inject it into the event since the field is already there.

CC @cshung who might know off the top of his head where the GC flags are stored or if they're being sent in a new/different event.

[Maoni0]

it's unfortunate this code was simply deleted, ironically it's the same way to get the startup flags for GC in coreclr as on .NET framework -

startupFlags = CorHost2::GetStartupFlags();

this is how the startup flags are obtained in InitializeStartupFlags in ceemain.cpp.