Garbage Collection (GC) in .NET.

  Let’s dive into the world of garbage collection (GC) in .NET. The garbage collector is a crucial component that manages memory allocation and reclaims memory for your application. Here’s a comprehensive overview:

1. Garbage Collection Basics:

   • The garbage collector automatically handles memory management, freeing developers from manual memory release tasks.
   • When you create an object using new, the runtime allocates memory for it from the managed heap.
   • As long as address space is available in the managed heap, the runtime continues allocating space for new objects.
   • Eventually, the garbage collector performs a collection to free memory by reclaiming unused objects.

2. Generational Garbage Collection:

   • The GC divides objects into three generations: Gen 0, Gen 1, and Gen 2.
   • Most objects die quickly (short-lived) in Gen 0 (e.g., request-scoped objects in a server app).
   • Gen 1 acts as a buffer between young and long-lived objects.
   • Gen 2 contains long-lived objects.
   • Gen 2 collections are also called full GCs.

3. Stages of Garbage Collection:

   • Marking Phase:
     • Identifies live objects by creating a list of them.
   • Relocating Phase:
     • Updates references to objects that will be compacted.
   • Compacting Phase:
     • Reclaims memory occupied by dead objects and compacts surviving objects.

4. Types of Garbage Collection:

   • Workstation GC:
     • Optimized for desktop applications.
     • Runs on a normal priority thread.
   • Server GC:
     • Default for ASP.NET Core apps.
     • Optimized for servers.
     • Creates a separate managed heap and GC thread per logical CPU.

5. Large Object Heap (LOH):

   • Definition: Objects greater than or equal to 85,000 bytes are considered large objects.
   • Placement: Large objects go on the LOH (sometimes called Gen 3).
   • Collection: Collected only during Gen 2 collections (full GCs).
   • Performance Implications:
     • Compacting large objects can be expensive.
     • LOH memory is usually not compacted to avoid moving large objects.
     • LOH is separate from the small object heap (SOH).

6. Size Threshold for LOH:

   • Any object allocation request for 85,000 bytes or more goes to the LOH.
   • This threshold was determined through performance tuning.