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• This talk dives deep!

• Examines internal data structures

• They will change!

• Internals knowledge not needed to write .NET apps

Quick Refresher: The Unmanaged World

Quick Refresher: The CLR

Agenda

1. Compilation

Agenda

2. Packaging: Assemblies

2. Metadata IL – Intermediate Language

• IL – The language for execution

• Independent of CPU and platform

• Created by Microsoft, external commercial and academic language/compiler writers

• Stack based virtual machine:

2. Metadata IL – Intermediate Language

• IL – The language for execution

• Independent of CPU and platform

• Created by Microsoft, external commercial and academic language/compiler writers

• Stack based:

2. Metadata IL – Intermediate Language

• IL – The language for execution

• Independent of CPU and platform

• Created by Microsoft, external commercial and academic language/compiler writers

• Stack based:

2. Metadata IL – Intermediate Language

• IL – The language for execution

• Independent of CPU and platform

• Created by Microsoft, external commercial and academic language/compiler writers

• Stack based:

2. Metadata IL – Intermediate Language

• IL – The language for execution

• Independent of CPU and platform

• Created by Microsoft, external commercial and academic language/compiler writers

• Stack based:

2. Metadata IL – Intermediate Language

• IL – The language for execution

• Independent of CPU and platform

• Created by Microsoft, external commercial and academic language/compiler writers

• Stack based:

2. Metadata IL – Intermediate Language

• IL – The language for execution

• Independent of CPU and platform

• Created by Microsoft, external commercial and academic language/compiler writers

• Stack based:

2. Metadata IL – Intermediate Language

• IL – The language for execution

• Independent of CPU and platform

• Created by Microsoft, external commercial and academic language/compiler writers

• Stack based:

2. Metadata IL – Verification

• When processing IL, runtime verifies the IL to make sure it’s “safe”

• Every IL construct is called with the correct amount of stack parameters
• Every method is called with the correct type and number of parameters

• Helps prevents buffer overflows, underruns

• Helps prevent security holes

• Safety allows multiple managed applications in the same process

Agenda

3. Loading and Layout Startup logic

• OS hands the image to a CLR shim (mscoree.dll)

• Which starts the runtime

• Runtime performs the following:

• Loads assembly in to memory and sets up the MD reader
• Resolves immediate dependencies
• Slurps metadata, creates internal data structures
• Starts execution at Assembly entry point

Agenda

4. Execution Invocation

4. Execution Invocation – JIT output

4. Execution JIT Optimizations

• Register Allocation

• locals, temps, evaluation stack

• Loop unroll

• Dead code elimination

• #define SOMETHING 0 if (SOMETHING > 10) a = x; // dead code statement

• Constant and Copy propagation

• Processor specific code generation

4. Execution JIT Optimizations

• Range check elimination

Agenda

5. Runtime services A look at the Garbage Collector

• Reference tracking (tracing) GC

• Large object heap – objects over 80k

• Generational (three gen)

• Mark sweep and compact

Agenda

More Information

• My Blog: http://blogs.msdn.com/brada

Questions?

BACKUP

New runtime features for V2.0

• Generics

• 64 bit (Itanium and x86-64)

• ReflectionOnly context

• Delegate Relaxation

• Lightweight Code Generation

• NGen/NGen services

• Stub based dispatch

• MDbg

• Edit and Continue

• BCL Enhancements

Generational GC

Generational GC

• Generations Dynamically Tuned

• CPU Cache Size
• Acceptable Fragmentation

• Older Generations are Larger / More Stable

• Require Collection Less Often
• Are More Expensive to Collect
• Can Have References to Newer Objects

What is Generics?

• Type checking, no boxing, no downcasts

• Increased sharing (typed collections)

• Instantiated at run-time, not compile-time

• Work for both reference and value types

• Code shared for reference types

• Exact run-time type information

What is Generics?

C# Generics

Bits & bytes under the hood

• New metadata tables

• Flags defines variance and special constraints

• GenericParamConstraint defines type constraints

Implementation choices

• Code sharing

• Modula 3 and ML use code sharing
• Type identity can be a problem
• Runtime type checking required

• Code specialization

• C++ templates uses specialization
• Code bloat can be a problem

4. Execution JIT Optimizations

• JIT Inlining (method example)

4. Execution JIT No inline == SLOW

4. Execution NextFib() method

4. Execution JIT Inlining == FAST!