1. From ‘dotnet run’
to “Hello World”
@matthewwarren
mattwarren.org

2. From ‘dotnet run’
to “Hello World”
http://raygun.com/apm

3. I ❤ ‘.NET Internals’

4. Understand one level below
your usual abstraction
Neal Ford

5. Demo – “Hello World”

6. Outline
• Main Components
• Hosting the runtime
• CLR Initialisation
• Type Loader
• JIT Compilation
• Everything Else

7. Main Components

8. CoreCLR Repository
• 2.6 million of source code, under src
• 8.2 million lines of test code
• 24,485 Files (7,466 source & 17,019 test)
– 6,626 C# (956 source & 5,670 test)
– 2,074 C and C++
– 3,701 IL
– 93 Assembler, 43 Python & 6 Perl!!

17. Virtual Machine (VM)
• Type System, Generics
• Built-in Types
• Loading types/classes
• Threading
• Exception Handling and Stack Walking
• Event Tracing and Profiling
• P/Invoke

18. Hosting

19. Hosting API
1. Identify the managed entry point
2. Find and load CoreCLR.dll
3. Get an ICLRRuntimeHost2 Instance
4. Set start-up flags and start the runtime
5. Preparing AppDomain settings
6. Create the AppDomain
7. Run managed code
8. Clean up
https://docs.microsoft.com/en-us/dotnet/core/tutorials/netcore-hosting

20. Demo – Hosting API

21. Initialisation

22. Initialising the CLR
• Phase 1 - Set-up infrastructure for all components
• Phase 2 - Initialise the core, low-level components
• Phase 3 - Start-up the low-level components, i.e. error
handling, profiling API, debugging
• Phase 4 - Start the main components, i.e. GC & AppDomains
• Phase 5 - Final setup and send out a notification
http://mattwarren.org/2017/02/07/The-68-things-the-CLR-does-before-
executing-a-single-line-of-your-code/

23. Demo - PerfView

24. ImageCourtesyof
JuliaEvans
@b0rk–jvns.ca

27. https://docs.microsoft.com/en-us/dotnet/standard/garbage-collection/fundamentals

28. Type Loader

31. http://mattwarren.org/2017/06/15/How-the-.NET-Rutime-loads-a-Type/

32. JIT Compilation

33. http://mattwarren.org/2017/12/15/How-does-.NET-JIT-a-
method-and-Tiered-Compilation/
Before JIT-ing

34. http://mattwarren.org/2017/12/15/How-does-.NET-JIT-a-
method-and-Tiered-Compilation/
Before JIT-ing
After JIT-ing

35. http://mattwarren.org/2017/12/15/How-does-.NET-JIT-a-
method-and-Tiered-Compilation/
Before JIT-ing
After JIT-ing with ‘Tiered Compilation’

36. http://mattwarren.org/2017/12/15/How-does-.NET-JIT-a-
method-and-Tiered-Compilation/
After JIT-ing with ‘Tiered Compilation’ - Optimised

37. Everything Else

38. Marshalling and P/Invoke

39. Resources
• http://mattwarren.org/tags/#Internals
– Resources for Learning about .NET Internals
– Exploring the Internals of the .NET Runtime
– Tools for Exploring .NET Internals
– Presentations and Talks covering '.NET Internals'
• Book of the Runtime (BotR)
– https://github.com/dotnet/coreclr/tree/master/Document
ation/botr

40. I ❤ ‘.NET Internals’
AMA