.NET Profiling for client apps (Desktop/CLI/Mobile)

[bruno-garcia]

Follow up from: #1955

Goals:

• Done on our fork: Fix the overhead until Create TraceLog (ETLX) without writing to file microsoft/perfview#1829 is addressed can be a blocker. We need to document this clearly while in beta, and address this with a fork or another approach to bypass file writing.
• Add SentryOptions.ProfilesSampleRate
• Add Benchmarks to validate the overhead is at about 5% (or whatever target we have right now)
• Dogfood with Symbol Collector CLI
• Documentation
• Bring Sentry.Profiling into Sentry #2314 (we'll punt this until we GA profiling)

Followups from: #2206

Some notes:

• We should support the lowest .NET version possible but for as long as we have no friction to do so. If supporting .NET 6 is the simplest/what we get OOTB, we should take that route. It's a new feature and we expect new customers/those upgrading to take advantage of. in other words: No .NET Framework or unsupported .NET Core as a goal.
• mark threads that don't run any user code as in-app=false
• should we filter-out sentry-specific/profiling-specific samples? marked as in-app=false
• provide debug_meta images if we want to show line numbers - this may need to be opt-in as it will likely add some runtime overhead
• it may be possible to handle GCstart & GCend events to show garbage collection
• Figure out thread names (we only have native thread IDs though so it seems to be a problem)
• Mobile/MAUI is a stretch goal (see: filipnavara/maui-sentry-profile)

[vaind]

Performance findings

I've done some benchmarks from various angles and what I've found (full results in this file) is:

• there's a fixed synchronous overhead at sampling-profiler start - on my machine, it's about 110 ms
• the overhead of profiling itself on a single-thread workload is about 4 %

The start-profiling overhead is unacceptable in all but very long transactions. Therefore, to make this GA, we would likely need to collect the profile continuously and slice it when a transaction runs, instead of starting to profile for each transaction.

[bruno-garcia]

microsoft/perfview#1867